* [PATCH v19 0/7] crash: Kernel handling of CPU and memory hot un/plug
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
Once the kdump service is loaded, if changes to CPUs or memory occur,
either by hot un/plug or off/onlining, the crash elfcorehdr must also
be updated.
The elfcorehdr describes to kdump the CPUs and memory in the system,
and any inaccuracies can result in a vmcore with missing CPU context
or memory regions.
The current solution utilizes udev to initiate an unload-then-reload
of the kdump image (eg. kernel, initrd, boot_params, puratory and
elfcorehdr) by the userspace kexec utility. In the original post I
outlined the significant performance problems related to offloading
this activity to userspace.
This patchset introduces a generic crash handler that registers with
the CPU and memory notifiers. Upon CPU or memory changes, from either
hot un/plug or off/onlining, this generic handler is invoked and
performs important housekeeping, for example obtaining the appropriate
lock, and then invokes an architecture specific handler to do the
appropriate elfcorehdr update.
In the case of x86_64, the arch specific handler generates a new
elfcorehdr, and overwrites the old one in memory; thus no involvement
with userspace needed.
To realize the benefits/test this patchset, one must make a couple
of minor changes to userspace:
- Prevent udev from updating kdump crash kernel on hot un/plug changes.
Add the following as the first lines to the RHEL udev rule file
/usr/lib/udev/rules.d/98-kexec.rules:
# The kernel handles updates to crash elfcorehdr for cpu and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
With this changeset applied, the two rules evaluate to false for
cpu and memory change events and thus skip the userspace
unload-then-reload of kdump.
- Change to the kexec_file_load for loading the kdump kernel:
Eg. on RHEL: in /usr/bin/kdumpctl, change to:
standard_kexec_args="-p -d -s"
which adds the -s to select kexec_file_load() syscall.
This kernel patchset also supports kexec_load() with a modified kexec
userspace utility. A working changeset to the kexec userspace utility
is posted to the kexec-tools mailing list here:
http://lists.infradead.org/pipermail/kexec/2022-October/026032.html
To use the kexec-tools patch, apply, build and install kexec-tools,
then change the kdumpctl's standard_kexec_args to replace the -s with
--hotplug. The removal of -s reverts to the kexec_load syscall and
the addition of --hotplug invokes the changes put forth in the
kexec-tools patch.
Regards,
eric
---
v19: 6mar2023
- Rebased onto 6.2.0
- Did away with offlinecpu, per Thomas Gleixner.
- Changed to CPUHP_BP_PREPARE_DYN instead of CPUHP_AP_ONLINE_DYN.
- Did away with elfcorehdr_index_valid, per Sourabh.
- Convert to for_each_possible_cpu() in crash_prepare_elf64_headers()
per Sourabh.
- Small optimization for x86 cpu changes.
v18: 31jan2023
https://lkml.org/lkml/2023/1/31/1356
- Rebased onto 6.2.0-rc6
- Renamed struct kimage member hotplug_event to hp_action, and
re-enumerated the KEXEC_CRASH_HP_x items, adding _NONE at 0.
- Moved to cpuhp state CPUHP_BP_PREPARE_DYN instead of
CPUHP_AP_ONLINE_DYN in order to minimize window of time CPU
is not reflected in elfcorehdr.
- Reworked some of the comments and commit messages to offer
more of the why, than what, per Thomas Gleixner.
v17: 18jan2023
https://lkml.org/lkml/2023/1/18/1420
- Rebased onto 6.2.0-rc4
- Moved a bit of code around so that kexec_load()-only builds
work, per Sourabh.
- Corrected computation of number of memory region Phdrs needed
when x86 memory hotplug is not enabled, per Baoquan.
v16: 5jan2023
https://lkml.org/lkml/2023/1/5/673
- Rebased onto 6.2.0-rc2
- Corrected error identified by Baoquan.
v15: 9dec2022
https://lkml.org/lkml/2022/12/9/520
- Rebased onto 6.1.0-rc8
- Replaced arch_un/map_crash_pages() with direct use of
kun/map_local_pages(), per Boris.
- Some x86 changes, per Boris.
v14: 16nov2022
https://lkml.org/lkml/2022/11/16/1645
- Rebased onto 6.1.0-rc5
- Introduced CRASH_HOTPLUG Kconfig item to better fine tune
compilation of feature components, per Boris.
- Removed hp_action parameter to arch_crash_handle_hotplug_event()
as it is unused.
v13: 31oct2022
https://lkml.org/lkml/2022/10/31/854
- Rebased onto 6.1.0-rc3, which means converting to use the new
kexec_trylock() away from mutex_lock(kexec_mutex).
- Moved arch_un/map_crash_pages() into kexec.h and default
implementation using k/unmap_local_pages().
- Changed more #ifdef's into IS_ENABLED()
- Changed CRASH_MAX_MEMORY_RANGES to 8192 from 32768, and it moved
into x86 crash.c as #define rather Kconfig item, per Boris.
- Check number of Phdrs against PN_XNUM, max possible.
v12: 9sep2022
https://lkml.org/lkml/2022/9/9/1358
- Rebased onto 6.0-rc4
- Addressed some minor formatting items, per Baoquan
v11: 26aug2022
https://lkml.org/lkml/2022/8/26/963
- Rebased onto 6.0-rc2
- Redid the rework of __weak to use asm/kexec.h, per Baoquan
- Reworked some comments and minor items, per Baoquan
v10: 21jul2022
https://lkml.org/lkml/2022/7/21/1007
- Rebased to 5.19.0-rc7
- Per Sourabh, corrected build issue with arch_un/map_crash_pages()
for architectures not supporting this feature.
- Per David Hildebrand, removed the WARN_ONCE() altogether.
- Per David Hansen, converted to use of kmap_local_page().
- Per Baoquan He, replaced use of __weak with the kexec technique.
v9: 13jun2022
https://lkml.org/lkml/2022/6/13/3382
- Rebased to 5.18.0
- Per Sourabh, moved crash_prepare_elf64_headers() into common
crash_core.c to avoid compile issues with kexec_load only path.
- Per David Hildebrand, replaced mutex_trylock() with mutex_lock().
- Changed the __weak arch_crash_handle_hotplug_event() to utilize
WARN_ONCE() instead of WARN(). Fix some formatting issues.
- Per Sourabh, introduced sysfs attribute crash_hotplug for memory
and CPUs; for use by userspace (udev) to determine if the kernel
performs crash hot un/plug support.
- Per Sourabh, moved the code detecting the elfcorehdr segment from
arch/x86 into crash_core:handle_hotplug_event() so both kexec_load
and kexec_file_load can benefit.
- Updated userspace kexec-tools kexec utility to reflect change to
using CRASH_MAX_MEMORY_RANGES and get_nr_cpus().
- Updated the new proposed udev rules to reflect using the sysfs
attributes crash_hotplug.
v8: 5may2022
https://lkml.org/lkml/2022/5/5/1133
- Per Borislav Petkov, eliminated CONFIG_CRASH_HOTPLUG in favor
of CONFIG_HOTPLUG_CPU || CONFIG_MEMORY_HOTPLUG, ie a new define
is not needed. Also use of IS_ENABLED() rather than #ifdef's.
Renamed crash_hotplug_handler() to handle_hotplug_event().
And other corrections.
- Per Baoquan, minimized the parameters to the arch_crash_
handle_hotplug_event() to hp_action and cpu.
- Introduce KEXEC_CRASH_HP_INVALID_CPU definition, per Baoquan.
- Per Sourabh Jain, renamed and repurposed CRASH_HOTPLUG_ELFCOREHDR_SZ
to CONFIG_CRASH_MAX_MEMORY_RANGES, mirroring kexec-tools change
by David Hildebrand. Folded this patch into the x86
kexec_file_load support patch.
v7: 13apr2022
https://lkml.org/lkml/2022/4/13/850
- Resolved parameter usage to crash_hotplug_handler(), per Baoquan.
v6: 1apr2022
https://lkml.org/lkml/2022/4/1/1203
- Reword commit messages and some comment cleanup per Baoquan.
- Changed elf_index to elfcorehdr_index for clarity.
- Minor code changes per Baoquan.
v5: 3mar2022
https://lkml.org/lkml/2022/3/3/674
- Reworded description of CRASH_HOTPLUG_ELFCOREHDR_SZ, per
David Hildenbrand.
- Refactored slightly a few patches per Baoquan recommendation.
v4: 9feb2022
https://lkml.org/lkml/2022/2/9/1406
- Refactored patches per Baoquan suggestsions.
- A few corrections, per Baoquan.
v3: 10jan2022
https://lkml.org/lkml/2022/1/10/1212
- Rebasing per Baoquan He request.
- Changed memory notifier per David Hildenbrand.
- Providing example kexec userspace change in cover letter.
RFC v2: 7dec2021
https://lkml.org/lkml/2021/12/7/1088
- Acting upon Baoquan He suggestion of removing elfcorehdr from
the purgatory list of segments, removed purgatory code from
patchset, and it is signficiantly simpler now.
RFC v1: 18nov2021
https://lkml.org/lkml/2021/11/18/845
- working patchset demonstrating kernel handling of hotplug
updates to x86 elfcorehdr for kexec_file_load
RFC: 14dec2020
https://lkml.org/lkml/2020/12/14/532
- proposed concept of allowing kernel to handle hotplug update
of elfcorehdr
---
Eric DeVolder (7):
crash: move a few code bits to setup support of crash hotplug
crash: add generic infrastructure for crash hotplug support
kexec: exclude elfcorehdr from the segment digest
crash: memory and cpu hotplug sysfs attributes
x86/crash: add x86 crash hotplug support
crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
x86/crash: optimize cpu changes
.../admin-guide/mm/memory-hotplug.rst | 8 +
Documentation/core-api/cpu_hotplug.rst | 18 +
arch/x86/Kconfig | 13 +
arch/x86/include/asm/kexec.h | 15 +
arch/x86/kernel/crash.c | 129 ++++++-
drivers/base/cpu.c | 14 +
drivers/base/memory.c | 13 +
include/linux/crash_core.h | 9 +
include/linux/kexec.h | 49 ++-
kernel/crash_core.c | 320 ++++++++++++++++++
kernel/kexec_core.c | 5 +
kernel/kexec_file.c | 187 +---------
12 files changed, 577 insertions(+), 203 deletions(-)
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* [PATCH v19 0/7] crash: Kernel handling of CPU and memory hot un/plug
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
Once the kdump service is loaded, if changes to CPUs or memory occur,
either by hot un/plug or off/onlining, the crash elfcorehdr must also
be updated.
The elfcorehdr describes to kdump the CPUs and memory in the system,
and any inaccuracies can result in a vmcore with missing CPU context
or memory regions.
The current solution utilizes udev to initiate an unload-then-reload
of the kdump image (eg. kernel, initrd, boot_params, puratory and
elfcorehdr) by the userspace kexec utility. In the original post I
outlined the significant performance problems related to offloading
this activity to userspace.
This patchset introduces a generic crash handler that registers with
the CPU and memory notifiers. Upon CPU or memory changes, from either
hot un/plug or off/onlining, this generic handler is invoked and
performs important housekeeping, for example obtaining the appropriate
lock, and then invokes an architecture specific handler to do the
appropriate elfcorehdr update.
In the case of x86_64, the arch specific handler generates a new
elfcorehdr, and overwrites the old one in memory; thus no involvement
with userspace needed.
To realize the benefits/test this patchset, one must make a couple
of minor changes to userspace:
- Prevent udev from updating kdump crash kernel on hot un/plug changes.
Add the following as the first lines to the RHEL udev rule file
/usr/lib/udev/rules.d/98-kexec.rules:
# The kernel handles updates to crash elfcorehdr for cpu and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
With this changeset applied, the two rules evaluate to false for
cpu and memory change events and thus skip the userspace
unload-then-reload of kdump.
- Change to the kexec_file_load for loading the kdump kernel:
Eg. on RHEL: in /usr/bin/kdumpctl, change to:
standard_kexec_args="-p -d -s"
which adds the -s to select kexec_file_load() syscall.
This kernel patchset also supports kexec_load() with a modified kexec
userspace utility. A working changeset to the kexec userspace utility
is posted to the kexec-tools mailing list here:
http://lists.infradead.org/pipermail/kexec/2022-October/026032.html
To use the kexec-tools patch, apply, build and install kexec-tools,
then change the kdumpctl's standard_kexec_args to replace the -s with
--hotplug. The removal of -s reverts to the kexec_load syscall and
the addition of --hotplug invokes the changes put forth in the
kexec-tools patch.
Regards,
eric
---
v19: 6mar2023
- Rebased onto 6.2.0
- Did away with offlinecpu, per Thomas Gleixner.
- Changed to CPUHP_BP_PREPARE_DYN instead of CPUHP_AP_ONLINE_DYN.
- Did away with elfcorehdr_index_valid, per Sourabh.
- Convert to for_each_possible_cpu() in crash_prepare_elf64_headers()
per Sourabh.
- Small optimization for x86 cpu changes.
v18: 31jan2023
https://lkml.org/lkml/2023/1/31/1356
- Rebased onto 6.2.0-rc6
- Renamed struct kimage member hotplug_event to hp_action, and
re-enumerated the KEXEC_CRASH_HP_x items, adding _NONE at 0.
- Moved to cpuhp state CPUHP_BP_PREPARE_DYN instead of
CPUHP_AP_ONLINE_DYN in order to minimize window of time CPU
is not reflected in elfcorehdr.
- Reworked some of the comments and commit messages to offer
more of the why, than what, per Thomas Gleixner.
v17: 18jan2023
https://lkml.org/lkml/2023/1/18/1420
- Rebased onto 6.2.0-rc4
- Moved a bit of code around so that kexec_load()-only builds
work, per Sourabh.
- Corrected computation of number of memory region Phdrs needed
when x86 memory hotplug is not enabled, per Baoquan.
v16: 5jan2023
https://lkml.org/lkml/2023/1/5/673
- Rebased onto 6.2.0-rc2
- Corrected error identified by Baoquan.
v15: 9dec2022
https://lkml.org/lkml/2022/12/9/520
- Rebased onto 6.1.0-rc8
- Replaced arch_un/map_crash_pages() with direct use of
kun/map_local_pages(), per Boris.
- Some x86 changes, per Boris.
v14: 16nov2022
https://lkml.org/lkml/2022/11/16/1645
- Rebased onto 6.1.0-rc5
- Introduced CRASH_HOTPLUG Kconfig item to better fine tune
compilation of feature components, per Boris.
- Removed hp_action parameter to arch_crash_handle_hotplug_event()
as it is unused.
v13: 31oct2022
https://lkml.org/lkml/2022/10/31/854
- Rebased onto 6.1.0-rc3, which means converting to use the new
kexec_trylock() away from mutex_lock(kexec_mutex).
- Moved arch_un/map_crash_pages() into kexec.h and default
implementation using k/unmap_local_pages().
- Changed more #ifdef's into IS_ENABLED()
- Changed CRASH_MAX_MEMORY_RANGES to 8192 from 32768, and it moved
into x86 crash.c as #define rather Kconfig item, per Boris.
- Check number of Phdrs against PN_XNUM, max possible.
v12: 9sep2022
https://lkml.org/lkml/2022/9/9/1358
- Rebased onto 6.0-rc4
- Addressed some minor formatting items, per Baoquan
v11: 26aug2022
https://lkml.org/lkml/2022/8/26/963
- Rebased onto 6.0-rc2
- Redid the rework of __weak to use asm/kexec.h, per Baoquan
- Reworked some comments and minor items, per Baoquan
v10: 21jul2022
https://lkml.org/lkml/2022/7/21/1007
- Rebased to 5.19.0-rc7
- Per Sourabh, corrected build issue with arch_un/map_crash_pages()
for architectures not supporting this feature.
- Per David Hildebrand, removed the WARN_ONCE() altogether.
- Per David Hansen, converted to use of kmap_local_page().
- Per Baoquan He, replaced use of __weak with the kexec technique.
v9: 13jun2022
https://lkml.org/lkml/2022/6/13/3382
- Rebased to 5.18.0
- Per Sourabh, moved crash_prepare_elf64_headers() into common
crash_core.c to avoid compile issues with kexec_load only path.
- Per David Hildebrand, replaced mutex_trylock() with mutex_lock().
- Changed the __weak arch_crash_handle_hotplug_event() to utilize
WARN_ONCE() instead of WARN(). Fix some formatting issues.
- Per Sourabh, introduced sysfs attribute crash_hotplug for memory
and CPUs; for use by userspace (udev) to determine if the kernel
performs crash hot un/plug support.
- Per Sourabh, moved the code detecting the elfcorehdr segment from
arch/x86 into crash_core:handle_hotplug_event() so both kexec_load
and kexec_file_load can benefit.
- Updated userspace kexec-tools kexec utility to reflect change to
using CRASH_MAX_MEMORY_RANGES and get_nr_cpus().
- Updated the new proposed udev rules to reflect using the sysfs
attributes crash_hotplug.
v8: 5may2022
https://lkml.org/lkml/2022/5/5/1133
- Per Borislav Petkov, eliminated CONFIG_CRASH_HOTPLUG in favor
of CONFIG_HOTPLUG_CPU || CONFIG_MEMORY_HOTPLUG, ie a new define
is not needed. Also use of IS_ENABLED() rather than #ifdef's.
Renamed crash_hotplug_handler() to handle_hotplug_event().
And other corrections.
- Per Baoquan, minimized the parameters to the arch_crash_
handle_hotplug_event() to hp_action and cpu.
- Introduce KEXEC_CRASH_HP_INVALID_CPU definition, per Baoquan.
- Per Sourabh Jain, renamed and repurposed CRASH_HOTPLUG_ELFCOREHDR_SZ
to CONFIG_CRASH_MAX_MEMORY_RANGES, mirroring kexec-tools change
by David Hildebrand. Folded this patch into the x86
kexec_file_load support patch.
v7: 13apr2022
https://lkml.org/lkml/2022/4/13/850
- Resolved parameter usage to crash_hotplug_handler(), per Baoquan.
v6: 1apr2022
https://lkml.org/lkml/2022/4/1/1203
- Reword commit messages and some comment cleanup per Baoquan.
- Changed elf_index to elfcorehdr_index for clarity.
- Minor code changes per Baoquan.
v5: 3mar2022
https://lkml.org/lkml/2022/3/3/674
- Reworded description of CRASH_HOTPLUG_ELFCOREHDR_SZ, per
David Hildenbrand.
- Refactored slightly a few patches per Baoquan recommendation.
v4: 9feb2022
https://lkml.org/lkml/2022/2/9/1406
- Refactored patches per Baoquan suggestsions.
- A few corrections, per Baoquan.
v3: 10jan2022
https://lkml.org/lkml/2022/1/10/1212
- Rebasing per Baoquan He request.
- Changed memory notifier per David Hildenbrand.
- Providing example kexec userspace change in cover letter.
RFC v2: 7dec2021
https://lkml.org/lkml/2021/12/7/1088
- Acting upon Baoquan He suggestion of removing elfcorehdr from
the purgatory list of segments, removed purgatory code from
patchset, and it is signficiantly simpler now.
RFC v1: 18nov2021
https://lkml.org/lkml/2021/11/18/845
- working patchset demonstrating kernel handling of hotplug
updates to x86 elfcorehdr for kexec_file_load
RFC: 14dec2020
https://lkml.org/lkml/2020/12/14/532
- proposed concept of allowing kernel to handle hotplug update
of elfcorehdr
---
Eric DeVolder (7):
crash: move a few code bits to setup support of crash hotplug
crash: add generic infrastructure for crash hotplug support
kexec: exclude elfcorehdr from the segment digest
crash: memory and cpu hotplug sysfs attributes
x86/crash: add x86 crash hotplug support
crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
x86/crash: optimize cpu changes
.../admin-guide/mm/memory-hotplug.rst | 8 +
Documentation/core-api/cpu_hotplug.rst | 18 +
arch/x86/Kconfig | 13 +
arch/x86/include/asm/kexec.h | 15 +
arch/x86/kernel/crash.c | 129 ++++++-
drivers/base/cpu.c | 14 +
drivers/base/memory.c | 13 +
include/linux/crash_core.h | 9 +
include/linux/kexec.h | 49 ++-
kernel/crash_core.c | 320 ++++++++++++++++++
kernel/kexec_core.c | 5 +
kernel/kexec_file.c | 187 +---------
12 files changed, 577 insertions(+), 203 deletions(-)
--
2.31.1
^ permalink raw reply [flat|nested] 46+ messages in thread
* [PATCH v19 1/7] crash: move a few code bits to setup support of crash hotplug
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
The crash hotplug support leans on the work for the kexec_file_load()
syscall. To also support the kexec_load() syscall, a few bits of code
need to be move outside of CONFIG_KEXEC_FILE. As such, these bits are
moved out of kexec_file.c and into a common location crash_core.c.
No functionality change intended.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
include/linux/kexec.h | 30 +++----
kernel/crash_core.c | 182 ++++++++++++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 181 -----------------------------------------
3 files changed, 197 insertions(+), 196 deletions(-)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 5dd4343c1bbe..582ea213467a 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -105,6 +105,21 @@ struct compat_kexec_segment {
};
#endif
+/* Alignment required for elf header segment */
+#define ELF_CORE_HEADER_ALIGN 4096
+
+struct crash_mem {
+ unsigned int max_nr_ranges;
+ unsigned int nr_ranges;
+ struct range ranges[];
+};
+
+extern int crash_exclude_mem_range(struct crash_mem *mem,
+ unsigned long long mstart,
+ unsigned long long mend);
+extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
+ void **addr, unsigned long *sz);
+
#ifdef CONFIG_KEXEC_FILE
struct purgatory_info {
/*
@@ -238,21 +253,6 @@ static inline int arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
}
#endif
-/* Alignment required for elf header segment */
-#define ELF_CORE_HEADER_ALIGN 4096
-
-struct crash_mem {
- unsigned int max_nr_ranges;
- unsigned int nr_ranges;
- struct range ranges[];
-};
-
-extern int crash_exclude_mem_range(struct crash_mem *mem,
- unsigned long long mstart,
- unsigned long long mend);
-extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
- void **addr, unsigned long *sz);
-
#ifndef arch_kexec_apply_relocations_add
/*
* arch_kexec_apply_relocations_add - apply relocations of type RELA
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 87ef6096823f..8a439b6d723b 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -10,6 +10,7 @@
#include <linux/utsname.h>
#include <linux/vmalloc.h>
#include <linux/sizes.h>
+#include <linux/kexec.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -314,6 +315,187 @@ static int __init parse_crashkernel_dummy(char *arg)
}
early_param("crashkernel", parse_crashkernel_dummy);
+int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
+ void **addr, unsigned long *sz)
+{
+ Elf64_Ehdr *ehdr;
+ Elf64_Phdr *phdr;
+ unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
+ unsigned char *buf;
+ unsigned int cpu, i;
+ unsigned long long notes_addr;
+ unsigned long mstart, mend;
+
+ /* extra phdr for vmcoreinfo ELF note */
+ nr_phdr = nr_cpus + 1;
+ nr_phdr += mem->nr_ranges;
+
+ /*
+ * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
+ * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
+ * I think this is required by tools like gdb. So same physical
+ * memory will be mapped in two ELF headers. One will contain kernel
+ * text virtual addresses and other will have __va(physical) addresses.
+ */
+
+ nr_phdr++;
+ elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
+ elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
+
+ buf = vzalloc(elf_sz);
+ if (!buf)
+ return -ENOMEM;
+
+ ehdr = (Elf64_Ehdr *)buf;
+ phdr = (Elf64_Phdr *)(ehdr + 1);
+ memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
+ ehdr->e_ident[EI_CLASS] = ELFCLASS64;
+ ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
+ ehdr->e_ident[EI_VERSION] = EV_CURRENT;
+ ehdr->e_ident[EI_OSABI] = ELF_OSABI;
+ memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
+ ehdr->e_type = ET_CORE;
+ ehdr->e_machine = ELF_ARCH;
+ ehdr->e_version = EV_CURRENT;
+ ehdr->e_phoff = sizeof(Elf64_Ehdr);
+ ehdr->e_ehsize = sizeof(Elf64_Ehdr);
+ ehdr->e_phentsize = sizeof(Elf64_Phdr);
+
+ /* Prepare one phdr of type PT_NOTE for each present CPU */
+ for_each_present_cpu(cpu) {
+ phdr->p_type = PT_NOTE;
+ notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
+ phdr->p_offset = phdr->p_paddr = notes_addr;
+ phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
+ (ehdr->e_phnum)++;
+ phdr++;
+ }
+
+ /* Prepare one PT_NOTE header for vmcoreinfo */
+ phdr->p_type = PT_NOTE;
+ phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
+ phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
+ (ehdr->e_phnum)++;
+ phdr++;
+
+ /* Prepare PT_LOAD type program header for kernel text region */
+ if (need_kernel_map) {
+ phdr->p_type = PT_LOAD;
+ phdr->p_flags = PF_R|PF_W|PF_X;
+ phdr->p_vaddr = (unsigned long) _text;
+ phdr->p_filesz = phdr->p_memsz = _end - _text;
+ phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
+ ehdr->e_phnum++;
+ phdr++;
+ }
+
+ /* Go through all the ranges in mem->ranges[] and prepare phdr */
+ for (i = 0; i < mem->nr_ranges; i++) {
+ mstart = mem->ranges[i].start;
+ mend = mem->ranges[i].end;
+
+ phdr->p_type = PT_LOAD;
+ phdr->p_flags = PF_R|PF_W|PF_X;
+ phdr->p_offset = mstart;
+
+ phdr->p_paddr = mstart;
+ phdr->p_vaddr = (unsigned long) __va(mstart);
+ phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
+ phdr->p_align = 0;
+ ehdr->e_phnum++;
+ pr_debug("Crash PT_LOAD ELF header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
+ phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
+ ehdr->e_phnum, phdr->p_offset);
+ phdr++;
+ }
+
+ *addr = buf;
+ *sz = elf_sz;
+ return 0;
+}
+
+int crash_exclude_mem_range(struct crash_mem *mem,
+ unsigned long long mstart, unsigned long long mend)
+{
+ int i, j;
+ unsigned long long start, end, p_start, p_end;
+ struct range temp_range = {0, 0};
+
+ for (i = 0; i < mem->nr_ranges; i++) {
+ start = mem->ranges[i].start;
+ end = mem->ranges[i].end;
+ p_start = mstart;
+ p_end = mend;
+
+ if (mstart > end || mend < start)
+ continue;
+
+ /* Truncate any area outside of range */
+ if (mstart < start)
+ p_start = start;
+ if (mend > end)
+ p_end = end;
+
+ /* Found completely overlapping range */
+ if (p_start == start && p_end == end) {
+ mem->ranges[i].start = 0;
+ mem->ranges[i].end = 0;
+ if (i < mem->nr_ranges - 1) {
+ /* Shift rest of the ranges to left */
+ for (j = i; j < mem->nr_ranges - 1; j++) {
+ mem->ranges[j].start =
+ mem->ranges[j+1].start;
+ mem->ranges[j].end =
+ mem->ranges[j+1].end;
+ }
+
+ /*
+ * Continue to check if there are another overlapping ranges
+ * from the current position because of shifting the above
+ * mem ranges.
+ */
+ i--;
+ mem->nr_ranges--;
+ continue;
+ }
+ mem->nr_ranges--;
+ return 0;
+ }
+
+ if (p_start > start && p_end < end) {
+ /* Split original range */
+ mem->ranges[i].end = p_start - 1;
+ temp_range.start = p_end + 1;
+ temp_range.end = end;
+ } else if (p_start != start)
+ mem->ranges[i].end = p_start - 1;
+ else
+ mem->ranges[i].start = p_end + 1;
+ break;
+ }
+
+ /* If a split happened, add the split to array */
+ if (!temp_range.end)
+ return 0;
+
+ /* Split happened */
+ if (i == mem->max_nr_ranges - 1)
+ return -ENOMEM;
+
+ /* Location where new range should go */
+ j = i + 1;
+ if (j < mem->nr_ranges) {
+ /* Move over all ranges one slot towards the end */
+ for (i = mem->nr_ranges - 1; i >= j; i--)
+ mem->ranges[i + 1] = mem->ranges[i];
+ }
+
+ mem->ranges[j].start = temp_range.start;
+ mem->ranges[j].end = temp_range.end;
+ mem->nr_ranges++;
+ return 0;
+}
+
Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
void *data, size_t data_len)
{
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index dd5983010b7b..ead3443e7f9d 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -1135,184 +1135,3 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
return 0;
}
#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
-
-int crash_exclude_mem_range(struct crash_mem *mem,
- unsigned long long mstart, unsigned long long mend)
-{
- int i, j;
- unsigned long long start, end, p_start, p_end;
- struct range temp_range = {0, 0};
-
- for (i = 0; i < mem->nr_ranges; i++) {
- start = mem->ranges[i].start;
- end = mem->ranges[i].end;
- p_start = mstart;
- p_end = mend;
-
- if (mstart > end || mend < start)
- continue;
-
- /* Truncate any area outside of range */
- if (mstart < start)
- p_start = start;
- if (mend > end)
- p_end = end;
-
- /* Found completely overlapping range */
- if (p_start == start && p_end == end) {
- mem->ranges[i].start = 0;
- mem->ranges[i].end = 0;
- if (i < mem->nr_ranges - 1) {
- /* Shift rest of the ranges to left */
- for (j = i; j < mem->nr_ranges - 1; j++) {
- mem->ranges[j].start =
- mem->ranges[j+1].start;
- mem->ranges[j].end =
- mem->ranges[j+1].end;
- }
-
- /*
- * Continue to check if there are another overlapping ranges
- * from the current position because of shifting the above
- * mem ranges.
- */
- i--;
- mem->nr_ranges--;
- continue;
- }
- mem->nr_ranges--;
- return 0;
- }
-
- if (p_start > start && p_end < end) {
- /* Split original range */
- mem->ranges[i].end = p_start - 1;
- temp_range.start = p_end + 1;
- temp_range.end = end;
- } else if (p_start != start)
- mem->ranges[i].end = p_start - 1;
- else
- mem->ranges[i].start = p_end + 1;
- break;
- }
-
- /* If a split happened, add the split to array */
- if (!temp_range.end)
- return 0;
-
- /* Split happened */
- if (i == mem->max_nr_ranges - 1)
- return -ENOMEM;
-
- /* Location where new range should go */
- j = i + 1;
- if (j < mem->nr_ranges) {
- /* Move over all ranges one slot towards the end */
- for (i = mem->nr_ranges - 1; i >= j; i--)
- mem->ranges[i + 1] = mem->ranges[i];
- }
-
- mem->ranges[j].start = temp_range.start;
- mem->ranges[j].end = temp_range.end;
- mem->nr_ranges++;
- return 0;
-}
-
-int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
- void **addr, unsigned long *sz)
-{
- Elf64_Ehdr *ehdr;
- Elf64_Phdr *phdr;
- unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
- unsigned char *buf;
- unsigned int cpu, i;
- unsigned long long notes_addr;
- unsigned long mstart, mend;
-
- /* extra phdr for vmcoreinfo ELF note */
- nr_phdr = nr_cpus + 1;
- nr_phdr += mem->nr_ranges;
-
- /*
- * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
- * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
- * I think this is required by tools like gdb. So same physical
- * memory will be mapped in two ELF headers. One will contain kernel
- * text virtual addresses and other will have __va(physical) addresses.
- */
-
- nr_phdr++;
- elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
- elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
-
- buf = vzalloc(elf_sz);
- if (!buf)
- return -ENOMEM;
-
- ehdr = (Elf64_Ehdr *)buf;
- phdr = (Elf64_Phdr *)(ehdr + 1);
- memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
- ehdr->e_ident[EI_CLASS] = ELFCLASS64;
- ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
- ehdr->e_ident[EI_VERSION] = EV_CURRENT;
- ehdr->e_ident[EI_OSABI] = ELF_OSABI;
- memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
- ehdr->e_type = ET_CORE;
- ehdr->e_machine = ELF_ARCH;
- ehdr->e_version = EV_CURRENT;
- ehdr->e_phoff = sizeof(Elf64_Ehdr);
- ehdr->e_ehsize = sizeof(Elf64_Ehdr);
- ehdr->e_phentsize = sizeof(Elf64_Phdr);
-
- /* Prepare one phdr of type PT_NOTE for each present CPU */
- for_each_present_cpu(cpu) {
- phdr->p_type = PT_NOTE;
- notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
- phdr->p_offset = phdr->p_paddr = notes_addr;
- phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
- (ehdr->e_phnum)++;
- phdr++;
- }
-
- /* Prepare one PT_NOTE header for vmcoreinfo */
- phdr->p_type = PT_NOTE;
- phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
- phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
- (ehdr->e_phnum)++;
- phdr++;
-
- /* Prepare PT_LOAD type program header for kernel text region */
- if (need_kernel_map) {
- phdr->p_type = PT_LOAD;
- phdr->p_flags = PF_R|PF_W|PF_X;
- phdr->p_vaddr = (unsigned long) _text;
- phdr->p_filesz = phdr->p_memsz = _end - _text;
- phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
- ehdr->e_phnum++;
- phdr++;
- }
-
- /* Go through all the ranges in mem->ranges[] and prepare phdr */
- for (i = 0; i < mem->nr_ranges; i++) {
- mstart = mem->ranges[i].start;
- mend = mem->ranges[i].end;
-
- phdr->p_type = PT_LOAD;
- phdr->p_flags = PF_R|PF_W|PF_X;
- phdr->p_offset = mstart;
-
- phdr->p_paddr = mstart;
- phdr->p_vaddr = (unsigned long) __va(mstart);
- phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
- phdr->p_align = 0;
- ehdr->e_phnum++;
- pr_debug("Crash PT_LOAD ELF header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
- phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
- ehdr->e_phnum, phdr->p_offset);
- phdr++;
- }
-
- *addr = buf;
- *sz = elf_sz;
- return 0;
-}
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 1/7] crash: move a few code bits to setup support of crash hotplug
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
The crash hotplug support leans on the work for the kexec_file_load()
syscall. To also support the kexec_load() syscall, a few bits of code
need to be move outside of CONFIG_KEXEC_FILE. As such, these bits are
moved out of kexec_file.c and into a common location crash_core.c.
No functionality change intended.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
include/linux/kexec.h | 30 +++----
kernel/crash_core.c | 182 ++++++++++++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 181 -----------------------------------------
3 files changed, 197 insertions(+), 196 deletions(-)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 5dd4343c1bbe..582ea213467a 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -105,6 +105,21 @@ struct compat_kexec_segment {
};
#endif
+/* Alignment required for elf header segment */
+#define ELF_CORE_HEADER_ALIGN 4096
+
+struct crash_mem {
+ unsigned int max_nr_ranges;
+ unsigned int nr_ranges;
+ struct range ranges[];
+};
+
+extern int crash_exclude_mem_range(struct crash_mem *mem,
+ unsigned long long mstart,
+ unsigned long long mend);
+extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
+ void **addr, unsigned long *sz);
+
#ifdef CONFIG_KEXEC_FILE
struct purgatory_info {
/*
@@ -238,21 +253,6 @@ static inline int arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
}
#endif
-/* Alignment required for elf header segment */
-#define ELF_CORE_HEADER_ALIGN 4096
-
-struct crash_mem {
- unsigned int max_nr_ranges;
- unsigned int nr_ranges;
- struct range ranges[];
-};
-
-extern int crash_exclude_mem_range(struct crash_mem *mem,
- unsigned long long mstart,
- unsigned long long mend);
-extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
- void **addr, unsigned long *sz);
-
#ifndef arch_kexec_apply_relocations_add
/*
* arch_kexec_apply_relocations_add - apply relocations of type RELA
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 87ef6096823f..8a439b6d723b 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -10,6 +10,7 @@
#include <linux/utsname.h>
#include <linux/vmalloc.h>
#include <linux/sizes.h>
+#include <linux/kexec.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -314,6 +315,187 @@ static int __init parse_crashkernel_dummy(char *arg)
}
early_param("crashkernel", parse_crashkernel_dummy);
+int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
+ void **addr, unsigned long *sz)
+{
+ Elf64_Ehdr *ehdr;
+ Elf64_Phdr *phdr;
+ unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
+ unsigned char *buf;
+ unsigned int cpu, i;
+ unsigned long long notes_addr;
+ unsigned long mstart, mend;
+
+ /* extra phdr for vmcoreinfo ELF note */
+ nr_phdr = nr_cpus + 1;
+ nr_phdr += mem->nr_ranges;
+
+ /*
+ * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
+ * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
+ * I think this is required by tools like gdb. So same physical
+ * memory will be mapped in two ELF headers. One will contain kernel
+ * text virtual addresses and other will have __va(physical) addresses.
+ */
+
+ nr_phdr++;
+ elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
+ elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
+
+ buf = vzalloc(elf_sz);
+ if (!buf)
+ return -ENOMEM;
+
+ ehdr = (Elf64_Ehdr *)buf;
+ phdr = (Elf64_Phdr *)(ehdr + 1);
+ memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
+ ehdr->e_ident[EI_CLASS] = ELFCLASS64;
+ ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
+ ehdr->e_ident[EI_VERSION] = EV_CURRENT;
+ ehdr->e_ident[EI_OSABI] = ELF_OSABI;
+ memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
+ ehdr->e_type = ET_CORE;
+ ehdr->e_machine = ELF_ARCH;
+ ehdr->e_version = EV_CURRENT;
+ ehdr->e_phoff = sizeof(Elf64_Ehdr);
+ ehdr->e_ehsize = sizeof(Elf64_Ehdr);
+ ehdr->e_phentsize = sizeof(Elf64_Phdr);
+
+ /* Prepare one phdr of type PT_NOTE for each present CPU */
+ for_each_present_cpu(cpu) {
+ phdr->p_type = PT_NOTE;
+ notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
+ phdr->p_offset = phdr->p_paddr = notes_addr;
+ phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
+ (ehdr->e_phnum)++;
+ phdr++;
+ }
+
+ /* Prepare one PT_NOTE header for vmcoreinfo */
+ phdr->p_type = PT_NOTE;
+ phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
+ phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
+ (ehdr->e_phnum)++;
+ phdr++;
+
+ /* Prepare PT_LOAD type program header for kernel text region */
+ if (need_kernel_map) {
+ phdr->p_type = PT_LOAD;
+ phdr->p_flags = PF_R|PF_W|PF_X;
+ phdr->p_vaddr = (unsigned long) _text;
+ phdr->p_filesz = phdr->p_memsz = _end - _text;
+ phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
+ ehdr->e_phnum++;
+ phdr++;
+ }
+
+ /* Go through all the ranges in mem->ranges[] and prepare phdr */
+ for (i = 0; i < mem->nr_ranges; i++) {
+ mstart = mem->ranges[i].start;
+ mend = mem->ranges[i].end;
+
+ phdr->p_type = PT_LOAD;
+ phdr->p_flags = PF_R|PF_W|PF_X;
+ phdr->p_offset = mstart;
+
+ phdr->p_paddr = mstart;
+ phdr->p_vaddr = (unsigned long) __va(mstart);
+ phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
+ phdr->p_align = 0;
+ ehdr->e_phnum++;
+ pr_debug("Crash PT_LOAD ELF header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
+ phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
+ ehdr->e_phnum, phdr->p_offset);
+ phdr++;
+ }
+
+ *addr = buf;
+ *sz = elf_sz;
+ return 0;
+}
+
+int crash_exclude_mem_range(struct crash_mem *mem,
+ unsigned long long mstart, unsigned long long mend)
+{
+ int i, j;
+ unsigned long long start, end, p_start, p_end;
+ struct range temp_range = {0, 0};
+
+ for (i = 0; i < mem->nr_ranges; i++) {
+ start = mem->ranges[i].start;
+ end = mem->ranges[i].end;
+ p_start = mstart;
+ p_end = mend;
+
+ if (mstart > end || mend < start)
+ continue;
+
+ /* Truncate any area outside of range */
+ if (mstart < start)
+ p_start = start;
+ if (mend > end)
+ p_end = end;
+
+ /* Found completely overlapping range */
+ if (p_start == start && p_end == end) {
+ mem->ranges[i].start = 0;
+ mem->ranges[i].end = 0;
+ if (i < mem->nr_ranges - 1) {
+ /* Shift rest of the ranges to left */
+ for (j = i; j < mem->nr_ranges - 1; j++) {
+ mem->ranges[j].start =
+ mem->ranges[j+1].start;
+ mem->ranges[j].end =
+ mem->ranges[j+1].end;
+ }
+
+ /*
+ * Continue to check if there are another overlapping ranges
+ * from the current position because of shifting the above
+ * mem ranges.
+ */
+ i--;
+ mem->nr_ranges--;
+ continue;
+ }
+ mem->nr_ranges--;
+ return 0;
+ }
+
+ if (p_start > start && p_end < end) {
+ /* Split original range */
+ mem->ranges[i].end = p_start - 1;
+ temp_range.start = p_end + 1;
+ temp_range.end = end;
+ } else if (p_start != start)
+ mem->ranges[i].end = p_start - 1;
+ else
+ mem->ranges[i].start = p_end + 1;
+ break;
+ }
+
+ /* If a split happened, add the split to array */
+ if (!temp_range.end)
+ return 0;
+
+ /* Split happened */
+ if (i == mem->max_nr_ranges - 1)
+ return -ENOMEM;
+
+ /* Location where new range should go */
+ j = i + 1;
+ if (j < mem->nr_ranges) {
+ /* Move over all ranges one slot towards the end */
+ for (i = mem->nr_ranges - 1; i >= j; i--)
+ mem->ranges[i + 1] = mem->ranges[i];
+ }
+
+ mem->ranges[j].start = temp_range.start;
+ mem->ranges[j].end = temp_range.end;
+ mem->nr_ranges++;
+ return 0;
+}
+
Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
void *data, size_t data_len)
{
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index dd5983010b7b..ead3443e7f9d 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -1135,184 +1135,3 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
return 0;
}
#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
-
-int crash_exclude_mem_range(struct crash_mem *mem,
- unsigned long long mstart, unsigned long long mend)
-{
- int i, j;
- unsigned long long start, end, p_start, p_end;
- struct range temp_range = {0, 0};
-
- for (i = 0; i < mem->nr_ranges; i++) {
- start = mem->ranges[i].start;
- end = mem->ranges[i].end;
- p_start = mstart;
- p_end = mend;
-
- if (mstart > end || mend < start)
- continue;
-
- /* Truncate any area outside of range */
- if (mstart < start)
- p_start = start;
- if (mend > end)
- p_end = end;
-
- /* Found completely overlapping range */
- if (p_start == start && p_end == end) {
- mem->ranges[i].start = 0;
- mem->ranges[i].end = 0;
- if (i < mem->nr_ranges - 1) {
- /* Shift rest of the ranges to left */
- for (j = i; j < mem->nr_ranges - 1; j++) {
- mem->ranges[j].start =
- mem->ranges[j+1].start;
- mem->ranges[j].end =
- mem->ranges[j+1].end;
- }
-
- /*
- * Continue to check if there are another overlapping ranges
- * from the current position because of shifting the above
- * mem ranges.
- */
- i--;
- mem->nr_ranges--;
- continue;
- }
- mem->nr_ranges--;
- return 0;
- }
-
- if (p_start > start && p_end < end) {
- /* Split original range */
- mem->ranges[i].end = p_start - 1;
- temp_range.start = p_end + 1;
- temp_range.end = end;
- } else if (p_start != start)
- mem->ranges[i].end = p_start - 1;
- else
- mem->ranges[i].start = p_end + 1;
- break;
- }
-
- /* If a split happened, add the split to array */
- if (!temp_range.end)
- return 0;
-
- /* Split happened */
- if (i == mem->max_nr_ranges - 1)
- return -ENOMEM;
-
- /* Location where new range should go */
- j = i + 1;
- if (j < mem->nr_ranges) {
- /* Move over all ranges one slot towards the end */
- for (i = mem->nr_ranges - 1; i >= j; i--)
- mem->ranges[i + 1] = mem->ranges[i];
- }
-
- mem->ranges[j].start = temp_range.start;
- mem->ranges[j].end = temp_range.end;
- mem->nr_ranges++;
- return 0;
-}
-
-int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
- void **addr, unsigned long *sz)
-{
- Elf64_Ehdr *ehdr;
- Elf64_Phdr *phdr;
- unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
- unsigned char *buf;
- unsigned int cpu, i;
- unsigned long long notes_addr;
- unsigned long mstart, mend;
-
- /* extra phdr for vmcoreinfo ELF note */
- nr_phdr = nr_cpus + 1;
- nr_phdr += mem->nr_ranges;
-
- /*
- * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
- * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
- * I think this is required by tools like gdb. So same physical
- * memory will be mapped in two ELF headers. One will contain kernel
- * text virtual addresses and other will have __va(physical) addresses.
- */
-
- nr_phdr++;
- elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
- elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
-
- buf = vzalloc(elf_sz);
- if (!buf)
- return -ENOMEM;
-
- ehdr = (Elf64_Ehdr *)buf;
- phdr = (Elf64_Phdr *)(ehdr + 1);
- memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
- ehdr->e_ident[EI_CLASS] = ELFCLASS64;
- ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
- ehdr->e_ident[EI_VERSION] = EV_CURRENT;
- ehdr->e_ident[EI_OSABI] = ELF_OSABI;
- memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD);
- ehdr->e_type = ET_CORE;
- ehdr->e_machine = ELF_ARCH;
- ehdr->e_version = EV_CURRENT;
- ehdr->e_phoff = sizeof(Elf64_Ehdr);
- ehdr->e_ehsize = sizeof(Elf64_Ehdr);
- ehdr->e_phentsize = sizeof(Elf64_Phdr);
-
- /* Prepare one phdr of type PT_NOTE for each present CPU */
- for_each_present_cpu(cpu) {
- phdr->p_type = PT_NOTE;
- notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
- phdr->p_offset = phdr->p_paddr = notes_addr;
- phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
- (ehdr->e_phnum)++;
- phdr++;
- }
-
- /* Prepare one PT_NOTE header for vmcoreinfo */
- phdr->p_type = PT_NOTE;
- phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
- phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
- (ehdr->e_phnum)++;
- phdr++;
-
- /* Prepare PT_LOAD type program header for kernel text region */
- if (need_kernel_map) {
- phdr->p_type = PT_LOAD;
- phdr->p_flags = PF_R|PF_W|PF_X;
- phdr->p_vaddr = (unsigned long) _text;
- phdr->p_filesz = phdr->p_memsz = _end - _text;
- phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
- ehdr->e_phnum++;
- phdr++;
- }
-
- /* Go through all the ranges in mem->ranges[] and prepare phdr */
- for (i = 0; i < mem->nr_ranges; i++) {
- mstart = mem->ranges[i].start;
- mend = mem->ranges[i].end;
-
- phdr->p_type = PT_LOAD;
- phdr->p_flags = PF_R|PF_W|PF_X;
- phdr->p_offset = mstart;
-
- phdr->p_paddr = mstart;
- phdr->p_vaddr = (unsigned long) __va(mstart);
- phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
- phdr->p_align = 0;
- ehdr->e_phnum++;
- pr_debug("Crash PT_LOAD ELF header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
- phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
- ehdr->e_phnum, phdr->p_offset);
- phdr++;
- }
-
- *addr = buf;
- *sz = elf_sz;
- return 0;
-}
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
To support crash hotplug, a mechanism is needed to update the crash
elfcorehdr upon CPU or memory changes (eg. hot un/plug or off/
onlining). The crash elfcorehdr describes the CPUs and memory to
be written into the vmcore.
To track CPU changes, callbacks are registered with the cpuhp
mechanism via cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN). The
crash hotplug elfcorehdr update has no explicit ordering requirement
(relative to other cpuhp states), so meets the criteria for
utilizing CPUHP_BP_PREPARE_DYN. CPUHP_BP_PREPARE_DYN is a dynamic
state and avoids the need to introduce a new state for crash
hotplug. Also, this is the last state in the PREPARE group, just
prior to the STARTING group, which is very close to the CPU
starting up in a plug/online situation, or stopping in a unplug/
offline situation. This minimizes the window of time during an
actual plug/online or unplug/offline situation in which the
elfcorehdr would be inaccurate. Note that for a CPU being unplugged
or offlined, the CPU will still be present in the list of CPUs
generated by crash_prepare_elf64_headers(). However, there is no
need to explicitly omit the CPU, see the discussion in the patch
'crash: change crash_prepare_elf64_headers() to
for_each_possible_cpu()'.
To track memory changes, a notifier is registered to capture the
memblock MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier().
The CPU callbacks and memory notifiers invoke crash_handle_hotplug_event()
which performs needed tasks and then dispatches the event to the
architecture specific arch_crash_handle_hotplug_event() to update the
elfcorehdr with the current state of CPUs and memory. During the
process, the kexec_lock is held.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
include/linux/crash_core.h | 9 +++
include/linux/kexec.h | 11 +++
kernel/crash_core.c | 138 +++++++++++++++++++++++++++++++++++++
kernel/kexec_core.c | 5 ++
4 files changed, 163 insertions(+)
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index de62a722431e..e14345cc7a22 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -84,4 +84,13 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,
int parse_crashkernel_low(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base);
+#define KEXEC_CRASH_HP_NONE 0
+#define KEXEC_CRASH_HP_ADD_CPU 1
+#define KEXEC_CRASH_HP_REMOVE_CPU 2
+#define KEXEC_CRASH_HP_ADD_MEMORY 3
+#define KEXEC_CRASH_HP_REMOVE_MEMORY 4
+#define KEXEC_CRASH_HP_INVALID_CPU -1U
+
+struct kimage;
+
#endif /* LINUX_CRASH_CORE_H */
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 582ea213467a..2dcc4d65f5a9 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -33,6 +33,7 @@ extern note_buf_t __percpu *crash_notes;
#include <linux/compat.h>
#include <linux/ioport.h>
#include <linux/module.h>
+#include <linux/highmem.h>
#include <asm/kexec.h>
/* Verify architecture specific macros are defined */
@@ -368,6 +369,12 @@ struct kimage {
struct purgatory_info purgatory_info;
#endif
+#ifdef CONFIG_CRASH_HOTPLUG
+ int hp_action;
+ int elfcorehdr_index;
+ bool elfcorehdr_updated;
+#endif
+
#ifdef CONFIG_IMA_KEXEC
/* Virtual address of IMA measurement buffer for kexec syscall */
void *ima_buffer;
@@ -497,6 +504,10 @@ static inline int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, g
static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) { }
#endif
+#ifndef arch_crash_handle_hotplug_event
+static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 8a439b6d723b..dba4b75f7541 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -11,6 +11,8 @@
#include <linux/vmalloc.h>
#include <linux/sizes.h>
#include <linux/kexec.h>
+#include <linux/memory.h>
+#include <linux/cpuhotplug.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -18,6 +20,7 @@
#include <crypto/sha1.h>
#include "kallsyms_internal.h"
+#include "kexec_internal.h"
/* vmcoreinfo stuff */
unsigned char *vmcoreinfo_data;
@@ -697,3 +700,138 @@ static int __init crash_save_vmcoreinfo_init(void)
}
subsys_initcall(crash_save_vmcoreinfo_init);
+
+#ifdef CONFIG_CRASH_HOTPLUG
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+/*
+ * To accurately reflect hot un/plug changes of cpu and memory resources
+ * (including onling and offlining of those resources), the elfcorehdr
+ * (which is passed to the crash kernel via the elfcorehdr= parameter)
+ * must be updated with the new list of CPUs and memories.
+ *
+ * In order to make changes to elfcorehdr, two conditions are needed:
+ * First, the segment containing the elfcorehdr must be large enough
+ * to permit a growing number of resources; the elfcorehdr memory size
+ * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
+ * Second, purgatory must explicitly exclude the elfcorehdr from the
+ * list of segments it checks (since the elfcorehdr changes and thus
+ * would require an update to purgatory itself to update the digest).
+ */
+static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
+{
+ /* Obtain lock while changing crash information */
+ if (kexec_trylock()) {
+
+ /* Check kdump is loaded */
+ if (kexec_crash_image) {
+ struct kimage *image = kexec_crash_image;
+
+ if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
+ hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
+ pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
+ else
+ pr_debug("hp_action %u\n", hp_action);
+
+ /*
+ * When the struct kimage is allocated, the elfcorehdr_index
+ * is set to -1. Find the segment containing the elfcorehdr,
+ * if not already found. This works for both the kexec_load
+ * and kexec_file_load paths.
+ */
+ if (image->elfcorehdr_index < 0) {
+ unsigned long mem;
+ unsigned char *ptr;
+ unsigned int n;
+
+ for (n = 0; n < image->nr_segments; n++) {
+ mem = image->segment[n].mem;
+ ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
+ if (ptr) {
+ /* The segment containing elfcorehdr */
+ if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
+ image->elfcorehdr_index = (int)n;
+ }
+ kunmap_local(ptr);
+ }
+ }
+ }
+
+ if (image->elfcorehdr_index < 0) {
+ pr_err("unable to locate elfcorehdr segment");
+ goto out;
+ }
+
+ /* Needed in order for the segments to be updated */
+ arch_kexec_unprotect_crashkres();
+
+ /* Differentiate between normal load and hotplug update */
+ image->hp_action = hp_action;
+
+ /* Now invoke arch-specific update handler */
+ arch_crash_handle_hotplug_event(image);
+
+ /* No longer handling a hotplug event */
+ image->hp_action = KEXEC_CRASH_HP_NONE;
+ image->elfcorehdr_updated = true;
+
+ /* Change back to read-only */
+ arch_kexec_protect_crashkres();
+ }
+
+out:
+ /* Release lock now that update complete */
+ kexec_unlock();
+ }
+}
+
+static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
+{
+ switch (val) {
+ case MEM_ONLINE:
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+
+ case MEM_OFFLINE:
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block crash_memhp_nb = {
+ .notifier_call = crash_memhp_notifier,
+ .priority = 0
+};
+
+static int crash_cpuhp_online(unsigned int cpu)
+{
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
+ return 0;
+}
+
+static int crash_cpuhp_offline(unsigned int cpu)
+{
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
+ return 0;
+}
+
+static int __init crash_hotplug_init(void)
+{
+ int result = 0;
+
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ register_memory_notifier(&crash_memhp_nb);
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
+ "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
+ }
+
+ return result;
+}
+
+subsys_initcall(crash_hotplug_init);
+#endif
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 969e8f52f7da..f2f9d41ce5df 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -276,6 +276,11 @@ struct kimage *do_kimage_alloc_init(void)
/* Initialize the list of unusable pages */
INIT_LIST_HEAD(&image->unusable_pages);
+#ifdef CONFIG_CRASH_HOTPLUG
+ image->elfcorehdr_index = -1;
+ image->elfcorehdr_updated = false;
+#endif
+
return image;
}
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
To support crash hotplug, a mechanism is needed to update the crash
elfcorehdr upon CPU or memory changes (eg. hot un/plug or off/
onlining). The crash elfcorehdr describes the CPUs and memory to
be written into the vmcore.
To track CPU changes, callbacks are registered with the cpuhp
mechanism via cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN). The
crash hotplug elfcorehdr update has no explicit ordering requirement
(relative to other cpuhp states), so meets the criteria for
utilizing CPUHP_BP_PREPARE_DYN. CPUHP_BP_PREPARE_DYN is a dynamic
state and avoids the need to introduce a new state for crash
hotplug. Also, this is the last state in the PREPARE group, just
prior to the STARTING group, which is very close to the CPU
starting up in a plug/online situation, or stopping in a unplug/
offline situation. This minimizes the window of time during an
actual plug/online or unplug/offline situation in which the
elfcorehdr would be inaccurate. Note that for a CPU being unplugged
or offlined, the CPU will still be present in the list of CPUs
generated by crash_prepare_elf64_headers(). However, there is no
need to explicitly omit the CPU, see the discussion in the patch
'crash: change crash_prepare_elf64_headers() to
for_each_possible_cpu()'.
To track memory changes, a notifier is registered to capture the
memblock MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier().
The CPU callbacks and memory notifiers invoke crash_handle_hotplug_event()
which performs needed tasks and then dispatches the event to the
architecture specific arch_crash_handle_hotplug_event() to update the
elfcorehdr with the current state of CPUs and memory. During the
process, the kexec_lock is held.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
include/linux/crash_core.h | 9 +++
include/linux/kexec.h | 11 +++
kernel/crash_core.c | 138 +++++++++++++++++++++++++++++++++++++
kernel/kexec_core.c | 5 ++
4 files changed, 163 insertions(+)
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index de62a722431e..e14345cc7a22 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -84,4 +84,13 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,
int parse_crashkernel_low(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base);
+#define KEXEC_CRASH_HP_NONE 0
+#define KEXEC_CRASH_HP_ADD_CPU 1
+#define KEXEC_CRASH_HP_REMOVE_CPU 2
+#define KEXEC_CRASH_HP_ADD_MEMORY 3
+#define KEXEC_CRASH_HP_REMOVE_MEMORY 4
+#define KEXEC_CRASH_HP_INVALID_CPU -1U
+
+struct kimage;
+
#endif /* LINUX_CRASH_CORE_H */
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 582ea213467a..2dcc4d65f5a9 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -33,6 +33,7 @@ extern note_buf_t __percpu *crash_notes;
#include <linux/compat.h>
#include <linux/ioport.h>
#include <linux/module.h>
+#include <linux/highmem.h>
#include <asm/kexec.h>
/* Verify architecture specific macros are defined */
@@ -368,6 +369,12 @@ struct kimage {
struct purgatory_info purgatory_info;
#endif
+#ifdef CONFIG_CRASH_HOTPLUG
+ int hp_action;
+ int elfcorehdr_index;
+ bool elfcorehdr_updated;
+#endif
+
#ifdef CONFIG_IMA_KEXEC
/* Virtual address of IMA measurement buffer for kexec syscall */
void *ima_buffer;
@@ -497,6 +504,10 @@ static inline int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, g
static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) { }
#endif
+#ifndef arch_crash_handle_hotplug_event
+static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 8a439b6d723b..dba4b75f7541 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -11,6 +11,8 @@
#include <linux/vmalloc.h>
#include <linux/sizes.h>
#include <linux/kexec.h>
+#include <linux/memory.h>
+#include <linux/cpuhotplug.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -18,6 +20,7 @@
#include <crypto/sha1.h>
#include "kallsyms_internal.h"
+#include "kexec_internal.h"
/* vmcoreinfo stuff */
unsigned char *vmcoreinfo_data;
@@ -697,3 +700,138 @@ static int __init crash_save_vmcoreinfo_init(void)
}
subsys_initcall(crash_save_vmcoreinfo_init);
+
+#ifdef CONFIG_CRASH_HOTPLUG
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+/*
+ * To accurately reflect hot un/plug changes of cpu and memory resources
+ * (including onling and offlining of those resources), the elfcorehdr
+ * (which is passed to the crash kernel via the elfcorehdr= parameter)
+ * must be updated with the new list of CPUs and memories.
+ *
+ * In order to make changes to elfcorehdr, two conditions are needed:
+ * First, the segment containing the elfcorehdr must be large enough
+ * to permit a growing number of resources; the elfcorehdr memory size
+ * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
+ * Second, purgatory must explicitly exclude the elfcorehdr from the
+ * list of segments it checks (since the elfcorehdr changes and thus
+ * would require an update to purgatory itself to update the digest).
+ */
+static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
+{
+ /* Obtain lock while changing crash information */
+ if (kexec_trylock()) {
+
+ /* Check kdump is loaded */
+ if (kexec_crash_image) {
+ struct kimage *image = kexec_crash_image;
+
+ if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
+ hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
+ pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
+ else
+ pr_debug("hp_action %u\n", hp_action);
+
+ /*
+ * When the struct kimage is allocated, the elfcorehdr_index
+ * is set to -1. Find the segment containing the elfcorehdr,
+ * if not already found. This works for both the kexec_load
+ * and kexec_file_load paths.
+ */
+ if (image->elfcorehdr_index < 0) {
+ unsigned long mem;
+ unsigned char *ptr;
+ unsigned int n;
+
+ for (n = 0; n < image->nr_segments; n++) {
+ mem = image->segment[n].mem;
+ ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
+ if (ptr) {
+ /* The segment containing elfcorehdr */
+ if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
+ image->elfcorehdr_index = (int)n;
+ }
+ kunmap_local(ptr);
+ }
+ }
+ }
+
+ if (image->elfcorehdr_index < 0) {
+ pr_err("unable to locate elfcorehdr segment");
+ goto out;
+ }
+
+ /* Needed in order for the segments to be updated */
+ arch_kexec_unprotect_crashkres();
+
+ /* Differentiate between normal load and hotplug update */
+ image->hp_action = hp_action;
+
+ /* Now invoke arch-specific update handler */
+ arch_crash_handle_hotplug_event(image);
+
+ /* No longer handling a hotplug event */
+ image->hp_action = KEXEC_CRASH_HP_NONE;
+ image->elfcorehdr_updated = true;
+
+ /* Change back to read-only */
+ arch_kexec_protect_crashkres();
+ }
+
+out:
+ /* Release lock now that update complete */
+ kexec_unlock();
+ }
+}
+
+static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
+{
+ switch (val) {
+ case MEM_ONLINE:
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+
+ case MEM_OFFLINE:
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block crash_memhp_nb = {
+ .notifier_call = crash_memhp_notifier,
+ .priority = 0
+};
+
+static int crash_cpuhp_online(unsigned int cpu)
+{
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
+ return 0;
+}
+
+static int crash_cpuhp_offline(unsigned int cpu)
+{
+ crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
+ return 0;
+}
+
+static int __init crash_hotplug_init(void)
+{
+ int result = 0;
+
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ register_memory_notifier(&crash_memhp_nb);
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
+ "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
+ }
+
+ return result;
+}
+
+subsys_initcall(crash_hotplug_init);
+#endif
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 969e8f52f7da..f2f9d41ce5df 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -276,6 +276,11 @@ struct kimage *do_kimage_alloc_init(void)
/* Initialize the list of unusable pages */
INIT_LIST_HEAD(&image->unusable_pages);
+#ifdef CONFIG_CRASH_HOTPLUG
+ image->elfcorehdr_index = -1;
+ image->elfcorehdr_updated = false;
+#endif
+
return image;
}
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 3/7] kexec: exclude elfcorehdr from the segment digest
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
When a crash kernel is loaded via the kexec_file_load() syscall, the
kernel places the various segments (ie crash kernel, crash initrd,
boot_params, elfcorehdr, purgatory, etc) in memory. For those
architectures that utilize purgatory, a hash digest of the segments
is calculated for integrity checking. This digest is embedded into
the purgatory image prior to placing purgatory in memory.
This patchset updates the elfcorehdr on CPU or memory changes.
However, changes to the elfcorehdr in turn cause purgatory
integrity checking to fail (at crash time, and no vmcore created).
Therefore, this patch explicitly excludes the elfcorehdr segment
from the list of segments used to create the digest. By doing so,
this permits updates to the elfcorehdr in response to CPU or memory
changes, and avoids the need to also recompute the hash digest and
reload purgatory.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
kernel/kexec_file.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index ead3443e7f9d..14e55fbc1ad7 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -723,6 +723,12 @@ static int kexec_calculate_store_digests(struct kimage *image)
for (j = i = 0; i < image->nr_segments; i++) {
struct kexec_segment *ksegment;
+#ifdef CONFIG_CRASH_HOTPLUG
+ /* Exclude elfcorehdr segment to allow future changes via hotplug */
+ if (j == image->elfcorehdr_index)
+ continue;
+#endif
+
ksegment = &image->segment[i];
/*
* Skip purgatory as it will be modified once we put digest
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 3/7] kexec: exclude elfcorehdr from the segment digest
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
When a crash kernel is loaded via the kexec_file_load() syscall, the
kernel places the various segments (ie crash kernel, crash initrd,
boot_params, elfcorehdr, purgatory, etc) in memory. For those
architectures that utilize purgatory, a hash digest of the segments
is calculated for integrity checking. This digest is embedded into
the purgatory image prior to placing purgatory in memory.
This patchset updates the elfcorehdr on CPU or memory changes.
However, changes to the elfcorehdr in turn cause purgatory
integrity checking to fail (at crash time, and no vmcore created).
Therefore, this patch explicitly excludes the elfcorehdr segment
from the list of segments used to create the digest. By doing so,
this permits updates to the elfcorehdr in response to CPU or memory
changes, and avoids the need to also recompute the hash digest and
reload purgatory.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
kernel/kexec_file.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index ead3443e7f9d..14e55fbc1ad7 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -723,6 +723,12 @@ static int kexec_calculate_store_digests(struct kimage *image)
for (j = i = 0; i < image->nr_segments; i++) {
struct kexec_segment *ksegment;
+#ifdef CONFIG_CRASH_HOTPLUG
+ /* Exclude elfcorehdr segment to allow future changes via hotplug */
+ if (j == image->elfcorehdr_index)
+ continue;
+#endif
+
ksegment = &image->segment[i];
/*
* Skip purgatory as it will be modified once we put digest
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 4/7] crash: memory and cpu hotplug sysfs attributes
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
This introduces the crash_hotplug attribute for memory and CPUs
for use by userspace. This change directly facilitates the udev
rule for managing userspace re-loading of the crash kernel upon
hot un/plug changes.
For memory, this changeset introduces the crash_hotplug attribute
to the /sys/devices/system/memory directory. For example:
# udevadm info --attribute-walk /sys/devices/system/memory/memory81
looking at device '/devices/system/memory/memory81':
KERNEL=="memory81"
SUBSYSTEM=="memory"
DRIVER==""
ATTR{online}=="1"
ATTR{phys_device}=="0"
ATTR{phys_index}=="00000051"
ATTR{removable}=="1"
ATTR{state}=="online"
ATTR{valid_zones}=="Movable"
looking at parent device '/devices/system/memory':
KERNELS=="memory"
SUBSYSTEMS==""
DRIVERS==""
ATTRS{auto_online_blocks}=="offline"
ATTRS{block_size_bytes}=="8000000"
ATTRS{crash_hotplug}=="1"
For CPUs, this changeset introduces the crash_hotplug attribute
to the /sys/devices/system/cpu directory. For example:
# udevadm info --attribute-walk /sys/devices/system/cpu/cpu0
looking at device '/devices/system/cpu/cpu0':
KERNEL=="cpu0"
SUBSYSTEM=="cpu"
DRIVER=="processor"
ATTR{crash_notes}=="277c38600"
ATTR{crash_notes_size}=="368"
ATTR{online}=="1"
looking at parent device '/devices/system/cpu':
KERNELS=="cpu"
SUBSYSTEMS==""
DRIVERS==""
ATTRS{crash_hotplug}=="1"
ATTRS{isolated}==""
ATTRS{kernel_max}=="8191"
ATTRS{nohz_full}==" (null)"
ATTRS{offline}=="4-7"
ATTRS{online}=="0-3"
ATTRS{possible}=="0-7"
ATTRS{present}=="0-3"
With these sysfs attributes in place, it is possible to efficiently
instruct the udev rule to skip crash kernel reloading.
For example, the following is the proposed udev rule change for RHEL
system 98-kexec.rules (as the first lines of the rule file):
# The kernel handles updates to crash elfcorehdr for cpu and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
When examined in the context of 98-kexec.rules, the above change
tests if crash_hotplug is set, and if so, it skips the userspace
initiated unload-then-reload of the crash kernel.
Cpu and memory checks are separated in accordance with
CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG kernel config options.
If an architecture supports, for example, memory hotplug but not
CPU hotplug, then the /sys/devices/system/memory/crash_hotplug
attribute file is present, but the /sys/devices/system/cpu/crash_hotplug
attribute file will NOT be present. Thus the udev rule will skip
userspace processing of memory hot un/plug events, but the udev
rule will evaluate false for CPU events, thus allowing userspace to
process cpu hot un/plug events (ie the unload-then-reload of the kdump
capture kernel).
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
.../admin-guide/mm/memory-hotplug.rst | 8 ++++++++
Documentation/core-api/cpu_hotplug.rst | 18 ++++++++++++++++++
drivers/base/cpu.c | 14 ++++++++++++++
drivers/base/memory.c | 13 +++++++++++++
include/linux/kexec.h | 8 ++++++++
5 files changed, 61 insertions(+)
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index a3c9e8ad8fa0..15fd1751a63c 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -293,6 +293,14 @@ The following files are currently defined:
Availability depends on the CONFIG_ARCH_MEMORY_PROBE
kernel configuration option.
``uevent`` read-write: generic udev file for device subsystems.
+``crash_hotplug`` read-only: when changes to the system memory map
+ occur due to hot un/plug of memory, this file contains
+ '1' if the kernel updates the kdump capture kernel memory
+ map itself (via elfcorehdr), or '0' if userspace must update
+ the kdump capture kernel memory map.
+
+ Availability depends on the CONFIG_MEMORY_HOTPLUG kernel
+ configuration option.
====================== =========================================================
.. note::
diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst
index f75778d37488..0c8dc3fe5f94 100644
--- a/Documentation/core-api/cpu_hotplug.rst
+++ b/Documentation/core-api/cpu_hotplug.rst
@@ -750,6 +750,24 @@ will receive all events. A script like::
can process the event further.
+When changes to the CPUs in the system occur, the sysfs file
+/sys/devices/system/cpu/crash_hotplug contains '1' if the kernel
+updates the kdump capture kernel list of CPUs itself (via elfcorehdr),
+or '0' if userspace must update the kdump capture kernel list of CPUs.
+
+The availability depends on the CONFIG_HOTPLUG_CPU kernel configuration
+option.
+
+To skip userspace processing of CPU hot un/plug events for kdump
+(ie the unload-then-reload to obtain a current list of CPUs), this sysfs
+file can be used in a udev rule as follows:
+
+ SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
+
+For a cpu hot un/plug event, if the architecture supports kernel updates
+of the elfcorehdr (which contains the list of CPUs), then the rule skips
+the unload-then-reload of the kdump capture kernel.
+
Kernel Inline Documentations Reference
======================================
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 4c98849577d4..fedbf87f9d13 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -293,6 +293,17 @@ static ssize_t print_cpus_nohz_full(struct device *dev,
static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
#endif
+#ifdef CONFIG_HOTPLUG_CPU
+#include <linux/kexec.h>
+static ssize_t crash_hotplug_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", crash_hotplug_cpu_support());
+}
+static DEVICE_ATTR_ADMIN_RO(crash_hotplug);
+#endif
+
static void cpu_device_release(struct device *dev)
{
/*
@@ -469,6 +480,9 @@ static struct attribute *cpu_root_attrs[] = {
#ifdef CONFIG_NO_HZ_FULL
&dev_attr_nohz_full.attr,
#endif
+#ifdef CONFIG_HOTPLUG_CPU
+ &dev_attr_crash_hotplug.attr,
+#endif
#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
&dev_attr_modalias.attr,
#endif
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index fe98fb8d94e5..a3f37cb57d79 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -495,6 +495,16 @@ static ssize_t auto_online_blocks_store(struct device *dev,
static DEVICE_ATTR_RW(auto_online_blocks);
+#ifdef CONFIG_MEMORY_HOTPLUG
+#include <linux/kexec.h>
+static ssize_t crash_hotplug_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", crash_hotplug_memory_support());
+}
+static DEVICE_ATTR_RO(crash_hotplug);
+#endif
+
/*
* Some architectures will have custom drivers to do this, and
* will not need to do it from userspace. The fake hot-add code
@@ -894,6 +904,9 @@ static struct attribute *memory_root_attrs[] = {
&dev_attr_block_size_bytes.attr,
&dev_attr_auto_online_blocks.attr,
+#ifdef CONFIG_MEMORY_HOTPLUG
+ &dev_attr_crash_hotplug.attr,
+#endif
NULL
};
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 2dcc4d65f5a9..5a0369b14d09 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -508,6 +508,14 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
#endif
+#ifndef crash_hotplug_cpu_support
+static inline int crash_hotplug_cpu_support(void) { return 0; }
+#endif
+
+#ifndef crash_hotplug_memory_support
+static inline int crash_hotplug_memory_support(void) { return 0; }
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 4/7] crash: memory and cpu hotplug sysfs attributes
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
This introduces the crash_hotplug attribute for memory and CPUs
for use by userspace. This change directly facilitates the udev
rule for managing userspace re-loading of the crash kernel upon
hot un/plug changes.
For memory, this changeset introduces the crash_hotplug attribute
to the /sys/devices/system/memory directory. For example:
# udevadm info --attribute-walk /sys/devices/system/memory/memory81
looking at device '/devices/system/memory/memory81':
KERNEL=="memory81"
SUBSYSTEM=="memory"
DRIVER==""
ATTR{online}=="1"
ATTR{phys_device}=="0"
ATTR{phys_index}=="00000051"
ATTR{removable}=="1"
ATTR{state}=="online"
ATTR{valid_zones}=="Movable"
looking at parent device '/devices/system/memory':
KERNELS=="memory"
SUBSYSTEMS==""
DRIVERS==""
ATTRS{auto_online_blocks}=="offline"
ATTRS{block_size_bytes}=="8000000"
ATTRS{crash_hotplug}=="1"
For CPUs, this changeset introduces the crash_hotplug attribute
to the /sys/devices/system/cpu directory. For example:
# udevadm info --attribute-walk /sys/devices/system/cpu/cpu0
looking at device '/devices/system/cpu/cpu0':
KERNEL=="cpu0"
SUBSYSTEM=="cpu"
DRIVER=="processor"
ATTR{crash_notes}=="277c38600"
ATTR{crash_notes_size}=="368"
ATTR{online}=="1"
looking at parent device '/devices/system/cpu':
KERNELS=="cpu"
SUBSYSTEMS==""
DRIVERS==""
ATTRS{crash_hotplug}=="1"
ATTRS{isolated}==""
ATTRS{kernel_max}=="8191"
ATTRS{nohz_full}==" (null)"
ATTRS{offline}=="4-7"
ATTRS{online}=="0-3"
ATTRS{possible}=="0-7"
ATTRS{present}=="0-3"
With these sysfs attributes in place, it is possible to efficiently
instruct the udev rule to skip crash kernel reloading.
For example, the following is the proposed udev rule change for RHEL
system 98-kexec.rules (as the first lines of the rule file):
# The kernel handles updates to crash elfcorehdr for cpu and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
When examined in the context of 98-kexec.rules, the above change
tests if crash_hotplug is set, and if so, it skips the userspace
initiated unload-then-reload of the crash kernel.
Cpu and memory checks are separated in accordance with
CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG kernel config options.
If an architecture supports, for example, memory hotplug but not
CPU hotplug, then the /sys/devices/system/memory/crash_hotplug
attribute file is present, but the /sys/devices/system/cpu/crash_hotplug
attribute file will NOT be present. Thus the udev rule will skip
userspace processing of memory hot un/plug events, but the udev
rule will evaluate false for CPU events, thus allowing userspace to
process cpu hot un/plug events (ie the unload-then-reload of the kdump
capture kernel).
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
.../admin-guide/mm/memory-hotplug.rst | 8 ++++++++
Documentation/core-api/cpu_hotplug.rst | 18 ++++++++++++++++++
drivers/base/cpu.c | 14 ++++++++++++++
drivers/base/memory.c | 13 +++++++++++++
include/linux/kexec.h | 8 ++++++++
5 files changed, 61 insertions(+)
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index a3c9e8ad8fa0..15fd1751a63c 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -293,6 +293,14 @@ The following files are currently defined:
Availability depends on the CONFIG_ARCH_MEMORY_PROBE
kernel configuration option.
``uevent`` read-write: generic udev file for device subsystems.
+``crash_hotplug`` read-only: when changes to the system memory map
+ occur due to hot un/plug of memory, this file contains
+ '1' if the kernel updates the kdump capture kernel memory
+ map itself (via elfcorehdr), or '0' if userspace must update
+ the kdump capture kernel memory map.
+
+ Availability depends on the CONFIG_MEMORY_HOTPLUG kernel
+ configuration option.
====================== =========================================================
.. note::
diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst
index f75778d37488..0c8dc3fe5f94 100644
--- a/Documentation/core-api/cpu_hotplug.rst
+++ b/Documentation/core-api/cpu_hotplug.rst
@@ -750,6 +750,24 @@ will receive all events. A script like::
can process the event further.
+When changes to the CPUs in the system occur, the sysfs file
+/sys/devices/system/cpu/crash_hotplug contains '1' if the kernel
+updates the kdump capture kernel list of CPUs itself (via elfcorehdr),
+or '0' if userspace must update the kdump capture kernel list of CPUs.
+
+The availability depends on the CONFIG_HOTPLUG_CPU kernel configuration
+option.
+
+To skip userspace processing of CPU hot un/plug events for kdump
+(ie the unload-then-reload to obtain a current list of CPUs), this sysfs
+file can be used in a udev rule as follows:
+
+ SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
+
+For a cpu hot un/plug event, if the architecture supports kernel updates
+of the elfcorehdr (which contains the list of CPUs), then the rule skips
+the unload-then-reload of the kdump capture kernel.
+
Kernel Inline Documentations Reference
======================================
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 4c98849577d4..fedbf87f9d13 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -293,6 +293,17 @@ static ssize_t print_cpus_nohz_full(struct device *dev,
static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
#endif
+#ifdef CONFIG_HOTPLUG_CPU
+#include <linux/kexec.h>
+static ssize_t crash_hotplug_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", crash_hotplug_cpu_support());
+}
+static DEVICE_ATTR_ADMIN_RO(crash_hotplug);
+#endif
+
static void cpu_device_release(struct device *dev)
{
/*
@@ -469,6 +480,9 @@ static struct attribute *cpu_root_attrs[] = {
#ifdef CONFIG_NO_HZ_FULL
&dev_attr_nohz_full.attr,
#endif
+#ifdef CONFIG_HOTPLUG_CPU
+ &dev_attr_crash_hotplug.attr,
+#endif
#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
&dev_attr_modalias.attr,
#endif
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index fe98fb8d94e5..a3f37cb57d79 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -495,6 +495,16 @@ static ssize_t auto_online_blocks_store(struct device *dev,
static DEVICE_ATTR_RW(auto_online_blocks);
+#ifdef CONFIG_MEMORY_HOTPLUG
+#include <linux/kexec.h>
+static ssize_t crash_hotplug_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", crash_hotplug_memory_support());
+}
+static DEVICE_ATTR_RO(crash_hotplug);
+#endif
+
/*
* Some architectures will have custom drivers to do this, and
* will not need to do it from userspace. The fake hot-add code
@@ -894,6 +904,9 @@ static struct attribute *memory_root_attrs[] = {
&dev_attr_block_size_bytes.attr,
&dev_attr_auto_online_blocks.attr,
+#ifdef CONFIG_MEMORY_HOTPLUG
+ &dev_attr_crash_hotplug.attr,
+#endif
NULL
};
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 2dcc4d65f5a9..5a0369b14d09 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -508,6 +508,14 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
#endif
+#ifndef crash_hotplug_cpu_support
+static inline int crash_hotplug_cpu_support(void) { return 0; }
+#endif
+
+#ifndef crash_hotplug_memory_support
+static inline int crash_hotplug_memory_support(void) { return 0; }
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 5/7] x86/crash: add x86 crash hotplug support
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
When CPU or memory is hot un/plugged, or off/onlined, the crash
elfcorehdr, which describes the CPUs and memory in the system,
must also be updated.
The segment containing the elfcorehdr is identified at run-time
in crash_core:crash_handle_hotplug_event(), which works for both
the kexec_load() and kexec_file_load() syscalls. A new elfcorehdr
is generated from the available CPUs and memory into a buffer,
and then installed over the top of the existing elfcorehdr.
In the patch 'kexec: exclude elfcorehdr from the segment digest'
the need to update purgatory due to the change in elfcorehdr was
eliminated. As a result, no changes to purgatory or boot_params
(as the elfcorehdr= kernel command line parameter pointer
remains unchanged and correct) are needed, just elfcorehdr.
To accommodate a growing number of resources via hotplug, the
elfcorehdr segment must be sufficiently large enough to accommodate
changes, see the CRASH_MAX_MEMORY_RANGES description. This is used
only on the kexec_file_load() syscall; for kexec_load() userspace
will need to size the segment similarly.
To accommodate kexec_load() syscall in the absence of
kexec_file_load() syscall support, and with CONFIG_CRASH_HOTPLUG
enabled, it is necessary to move prepare_elf_headers() and
dependents outside of CONFIG_KEXEC_FILE.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/Kconfig | 13 ++++
arch/x86/include/asm/kexec.h | 15 +++++
arch/x86/kernel/crash.c | 119 ++++++++++++++++++++++++++++++++---
3 files changed, 140 insertions(+), 7 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3604074a878b..2ca5e19b8f19 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2119,6 +2119,19 @@ config CRASH_DUMP
(CONFIG_RELOCATABLE=y).
For more details see Documentation/admin-guide/kdump/kdump.rst
+config CRASH_HOTPLUG
+ bool "Update the crash elfcorehdr on system configuration changes"
+ default n
+ depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG)
+ help
+ Enable direct update to the crash elfcorehdr (which contains
+ the list of CPUs and memory regions to be dumped upon a crash)
+ in response to hot plug/unplug or online/offline of CPUs or
+ memory. This is a much more advanced approach than userspace
+ attempting that.
+
+ If unsure, say Y.
+
config KEXEC_JUMP
bool "kexec jump"
depends on KEXEC && HIBERNATION
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index a3760ca796aa..1bc852ce347d 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -212,6 +212,21 @@ typedef void crash_vmclear_fn(void);
extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
extern void kdump_nmi_shootdown_cpus(void);
+#ifdef CONFIG_CRASH_HOTPLUG
+void arch_crash_handle_hotplug_event(struct kimage *image);
+#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
+
+#ifdef CONFIG_HOTPLUG_CPU
+static inline int crash_hotplug_cpu_support(void) { return 1; }
+#define crash_hotplug_cpu_support crash_hotplug_cpu_support
+#endif
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static inline int crash_hotplug_memory_support(void) { return 1; }
+#define crash_hotplug_memory_support crash_hotplug_memory_support
+#endif
+#endif
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_KEXEC_H */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 305514431f26..c9aaec9de775 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -42,6 +42,21 @@
#include <asm/crash.h>
#include <asm/cmdline.h>
+/*
+ * For the kexec_file_load() syscall path, specify the maximum number of
+ * memory regions that the elfcorehdr buffer/segment can accommodate.
+ * These regions are obtained via walk_system_ram_res(); eg. the
+ * 'System RAM' entries in /proc/iomem.
+ * This value is combined with NR_CPUS_DEFAULT and multiplied by
+ * sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/
+ * segment size.
+ * The value 8192, for example, covers a (sparsely populated) 1TiB system
+ * consisting of 128MiB memblocks, while resulting in an elfcorehdr
+ * memory buffer/segment size under 1MiB. This represents a sane choice
+ * to accommodate both baremetal and virtual machine configurations.
+ */
+#define CRASH_MAX_MEMORY_RANGES 8192
+
/* Used while preparing memory map entries for second kernel */
struct crash_memmap_data {
struct boot_params *params;
@@ -173,8 +188,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
crash_save_cpu(regs, safe_smp_processor_id());
}
-#ifdef CONFIG_KEXEC_FILE
-
static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
{
unsigned int *nr_ranges = arg;
@@ -246,7 +259,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
/* Prepare elf headers. Return addr and size */
static int prepare_elf_headers(struct kimage *image, void **addr,
- unsigned long *sz)
+ unsigned long *sz, unsigned long *nr_mem_ranges)
{
struct crash_mem *cmem;
int ret;
@@ -264,6 +277,9 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
if (ret)
goto out;
+ /* Return the computed number of memory ranges, for hotplug usage */
+ *nr_mem_ranges = cmem->nr_ranges;
+
/* By default prepare 64bit headers */
ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
@@ -272,6 +288,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
return ret;
}
+#ifdef CONFIG_KEXEC_FILE
static int add_e820_entry(struct boot_params *params, struct e820_entry *entry)
{
unsigned int nr_e820_entries;
@@ -386,18 +403,42 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
int crash_load_segments(struct kimage *image)
{
int ret;
+ unsigned long pnum = 0;
struct kexec_buf kbuf = { .image = image, .buf_min = 0,
.buf_max = ULONG_MAX, .top_down = false };
/* Prepare elf headers and add a segment */
- ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
+ ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz, &pnum);
if (ret)
return ret;
- image->elf_headers = kbuf.buffer;
- image->elf_headers_sz = kbuf.bufsz;
+ image->elf_headers = kbuf.buffer;
+ image->elf_headers_sz = kbuf.bufsz;
+ kbuf.memsz = kbuf.bufsz;
+
+#ifdef CONFIG_CRASH_HOTPLUG
+ /*
+ * Ensure the elfcorehdr segment large enough for hotplug changes.
+ * Account for VMCOREINFO and kernel_map and maximum CPUs.
+ */
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ pnum = 2 + CONFIG_NR_CPUS_DEFAULT + CRASH_MAX_MEMORY_RANGES;
+ else
+ pnum += 2 + CONFIG_NR_CPUS_DEFAULT;
+
+ if (pnum < (unsigned long)PN_XNUM) {
+ kbuf.memsz = pnum * sizeof(Elf64_Phdr);
+ kbuf.memsz += sizeof(Elf64_Ehdr);
+
+ image->elfcorehdr_index = image->nr_segments;
+
+ /* Mark as usable to crash kernel, else crash kernel fails on boot */
+ image->elf_headers_sz = kbuf.memsz;
+ } else {
+ pr_err("number of Phdrs %lu exceeds max\n", pnum);
+ }
+#endif
- kbuf.memsz = kbuf.bufsz;
kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
ret = kexec_add_buffer(&kbuf);
@@ -410,3 +451,67 @@ int crash_load_segments(struct kimage *image)
return ret;
}
#endif /* CONFIG_KEXEC_FILE */
+
+#ifdef CONFIG_CRASH_HOTPLUG
+
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+
+/**
+ * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
+ * @image: the active struct kimage
+ *
+ * The new elfcorehdr is prepared in a kernel buffer, and then it is
+ * written on top of the existing/old elfcorehdr.
+ */
+void arch_crash_handle_hotplug_event(struct kimage *image)
+{
+ void *elfbuf = NULL, *old_elfcorehdr;
+ unsigned long nr_mem_ranges;
+ unsigned long mem, memsz;
+ unsigned long elfsz = 0;
+
+ /*
+ * Create the new elfcorehdr reflecting the changes to CPU and/or
+ * memory resources.
+ */
+ if (prepare_elf_headers(image, &elfbuf, &elfsz, &nr_mem_ranges)) {
+ pr_err("unable to prepare elfcore headers");
+ goto out;
+ }
+
+ /*
+ * Obtain address and size of the elfcorehdr segment, and
+ * check it against the new elfcorehdr buffer.
+ */
+ mem = image->segment[image->elfcorehdr_index].mem;
+ memsz = image->segment[image->elfcorehdr_index].memsz;
+ if (elfsz > memsz) {
+ pr_err("update elfcorehdr elfsz %lu > memsz %lu",
+ elfsz, memsz);
+ goto out;
+ }
+
+ /*
+ * Copy new elfcorehdr over the old elfcorehdr at destination.
+ */
+ old_elfcorehdr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
+ if (!old_elfcorehdr) {
+ pr_err("updating elfcorehdr failed\n");
+ goto out;
+ }
+
+ /*
+ * Temporarily invalidate the crash image while the
+ * elfcorehdr is updated.
+ */
+ xchg(&kexec_crash_image, NULL);
+ memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz);
+ xchg(&kexec_crash_image, image);
+ kunmap_local(old_elfcorehdr);
+ pr_debug("updated elfcorehdr\n");
+
+out:
+ vfree(elfbuf);
+}
+#endif
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 5/7] x86/crash: add x86 crash hotplug support
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
When CPU or memory is hot un/plugged, or off/onlined, the crash
elfcorehdr, which describes the CPUs and memory in the system,
must also be updated.
The segment containing the elfcorehdr is identified at run-time
in crash_core:crash_handle_hotplug_event(), which works for both
the kexec_load() and kexec_file_load() syscalls. A new elfcorehdr
is generated from the available CPUs and memory into a buffer,
and then installed over the top of the existing elfcorehdr.
In the patch 'kexec: exclude elfcorehdr from the segment digest'
the need to update purgatory due to the change in elfcorehdr was
eliminated. As a result, no changes to purgatory or boot_params
(as the elfcorehdr= kernel command line parameter pointer
remains unchanged and correct) are needed, just elfcorehdr.
To accommodate a growing number of resources via hotplug, the
elfcorehdr segment must be sufficiently large enough to accommodate
changes, see the CRASH_MAX_MEMORY_RANGES description. This is used
only on the kexec_file_load() syscall; for kexec_load() userspace
will need to size the segment similarly.
To accommodate kexec_load() syscall in the absence of
kexec_file_load() syscall support, and with CONFIG_CRASH_HOTPLUG
enabled, it is necessary to move prepare_elf_headers() and
dependents outside of CONFIG_KEXEC_FILE.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/Kconfig | 13 ++++
arch/x86/include/asm/kexec.h | 15 +++++
arch/x86/kernel/crash.c | 119 ++++++++++++++++++++++++++++++++---
3 files changed, 140 insertions(+), 7 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3604074a878b..2ca5e19b8f19 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2119,6 +2119,19 @@ config CRASH_DUMP
(CONFIG_RELOCATABLE=y).
For more details see Documentation/admin-guide/kdump/kdump.rst
+config CRASH_HOTPLUG
+ bool "Update the crash elfcorehdr on system configuration changes"
+ default n
+ depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG)
+ help
+ Enable direct update to the crash elfcorehdr (which contains
+ the list of CPUs and memory regions to be dumped upon a crash)
+ in response to hot plug/unplug or online/offline of CPUs or
+ memory. This is a much more advanced approach than userspace
+ attempting that.
+
+ If unsure, say Y.
+
config KEXEC_JUMP
bool "kexec jump"
depends on KEXEC && HIBERNATION
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index a3760ca796aa..1bc852ce347d 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -212,6 +212,21 @@ typedef void crash_vmclear_fn(void);
extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
extern void kdump_nmi_shootdown_cpus(void);
+#ifdef CONFIG_CRASH_HOTPLUG
+void arch_crash_handle_hotplug_event(struct kimage *image);
+#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
+
+#ifdef CONFIG_HOTPLUG_CPU
+static inline int crash_hotplug_cpu_support(void) { return 1; }
+#define crash_hotplug_cpu_support crash_hotplug_cpu_support
+#endif
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static inline int crash_hotplug_memory_support(void) { return 1; }
+#define crash_hotplug_memory_support crash_hotplug_memory_support
+#endif
+#endif
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_KEXEC_H */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 305514431f26..c9aaec9de775 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -42,6 +42,21 @@
#include <asm/crash.h>
#include <asm/cmdline.h>
+/*
+ * For the kexec_file_load() syscall path, specify the maximum number of
+ * memory regions that the elfcorehdr buffer/segment can accommodate.
+ * These regions are obtained via walk_system_ram_res(); eg. the
+ * 'System RAM' entries in /proc/iomem.
+ * This value is combined with NR_CPUS_DEFAULT and multiplied by
+ * sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/
+ * segment size.
+ * The value 8192, for example, covers a (sparsely populated) 1TiB system
+ * consisting of 128MiB memblocks, while resulting in an elfcorehdr
+ * memory buffer/segment size under 1MiB. This represents a sane choice
+ * to accommodate both baremetal and virtual machine configurations.
+ */
+#define CRASH_MAX_MEMORY_RANGES 8192
+
/* Used while preparing memory map entries for second kernel */
struct crash_memmap_data {
struct boot_params *params;
@@ -173,8 +188,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
crash_save_cpu(regs, safe_smp_processor_id());
}
-#ifdef CONFIG_KEXEC_FILE
-
static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
{
unsigned int *nr_ranges = arg;
@@ -246,7 +259,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
/* Prepare elf headers. Return addr and size */
static int prepare_elf_headers(struct kimage *image, void **addr,
- unsigned long *sz)
+ unsigned long *sz, unsigned long *nr_mem_ranges)
{
struct crash_mem *cmem;
int ret;
@@ -264,6 +277,9 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
if (ret)
goto out;
+ /* Return the computed number of memory ranges, for hotplug usage */
+ *nr_mem_ranges = cmem->nr_ranges;
+
/* By default prepare 64bit headers */
ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
@@ -272,6 +288,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
return ret;
}
+#ifdef CONFIG_KEXEC_FILE
static int add_e820_entry(struct boot_params *params, struct e820_entry *entry)
{
unsigned int nr_e820_entries;
@@ -386,18 +403,42 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
int crash_load_segments(struct kimage *image)
{
int ret;
+ unsigned long pnum = 0;
struct kexec_buf kbuf = { .image = image, .buf_min = 0,
.buf_max = ULONG_MAX, .top_down = false };
/* Prepare elf headers and add a segment */
- ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
+ ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz, &pnum);
if (ret)
return ret;
- image->elf_headers = kbuf.buffer;
- image->elf_headers_sz = kbuf.bufsz;
+ image->elf_headers = kbuf.buffer;
+ image->elf_headers_sz = kbuf.bufsz;
+ kbuf.memsz = kbuf.bufsz;
+
+#ifdef CONFIG_CRASH_HOTPLUG
+ /*
+ * Ensure the elfcorehdr segment large enough for hotplug changes.
+ * Account for VMCOREINFO and kernel_map and maximum CPUs.
+ */
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ pnum = 2 + CONFIG_NR_CPUS_DEFAULT + CRASH_MAX_MEMORY_RANGES;
+ else
+ pnum += 2 + CONFIG_NR_CPUS_DEFAULT;
+
+ if (pnum < (unsigned long)PN_XNUM) {
+ kbuf.memsz = pnum * sizeof(Elf64_Phdr);
+ kbuf.memsz += sizeof(Elf64_Ehdr);
+
+ image->elfcorehdr_index = image->nr_segments;
+
+ /* Mark as usable to crash kernel, else crash kernel fails on boot */
+ image->elf_headers_sz = kbuf.memsz;
+ } else {
+ pr_err("number of Phdrs %lu exceeds max\n", pnum);
+ }
+#endif
- kbuf.memsz = kbuf.bufsz;
kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
ret = kexec_add_buffer(&kbuf);
@@ -410,3 +451,67 @@ int crash_load_segments(struct kimage *image)
return ret;
}
#endif /* CONFIG_KEXEC_FILE */
+
+#ifdef CONFIG_CRASH_HOTPLUG
+
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+
+/**
+ * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
+ * @image: the active struct kimage
+ *
+ * The new elfcorehdr is prepared in a kernel buffer, and then it is
+ * written on top of the existing/old elfcorehdr.
+ */
+void arch_crash_handle_hotplug_event(struct kimage *image)
+{
+ void *elfbuf = NULL, *old_elfcorehdr;
+ unsigned long nr_mem_ranges;
+ unsigned long mem, memsz;
+ unsigned long elfsz = 0;
+
+ /*
+ * Create the new elfcorehdr reflecting the changes to CPU and/or
+ * memory resources.
+ */
+ if (prepare_elf_headers(image, &elfbuf, &elfsz, &nr_mem_ranges)) {
+ pr_err("unable to prepare elfcore headers");
+ goto out;
+ }
+
+ /*
+ * Obtain address and size of the elfcorehdr segment, and
+ * check it against the new elfcorehdr buffer.
+ */
+ mem = image->segment[image->elfcorehdr_index].mem;
+ memsz = image->segment[image->elfcorehdr_index].memsz;
+ if (elfsz > memsz) {
+ pr_err("update elfcorehdr elfsz %lu > memsz %lu",
+ elfsz, memsz);
+ goto out;
+ }
+
+ /*
+ * Copy new elfcorehdr over the old elfcorehdr at destination.
+ */
+ old_elfcorehdr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
+ if (!old_elfcorehdr) {
+ pr_err("updating elfcorehdr failed\n");
+ goto out;
+ }
+
+ /*
+ * Temporarily invalidate the crash image while the
+ * elfcorehdr is updated.
+ */
+ xchg(&kexec_crash_image, NULL);
+ memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz);
+ xchg(&kexec_crash_image, image);
+ kunmap_local(old_elfcorehdr);
+ pr_debug("updated elfcorehdr\n");
+
+out:
+ vfree(elfbuf);
+}
+#endif
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
The function crash_prepare_elf64_headers() generates the elfcorehdr
which describes the cpus and memory in the system for the crash kernel.
In particular, it writes out ELF PT_NOTEs for memory regions and the
cpus in the system.
With respect to the cpus, the current implementation utilizes
for_each_present_cpu() which means that as cpus are added and removed,
the elfcorehdr must again be updated to reflect the new set of cpus.
The reasoning behind the change to use for_each_possible_cpu(), is:
- At kernel boot time, all percpu crash_notes are allocated for all
possible cpus; that is, crash_notes are not allocated dynamically
when cpus are plugged/unplugged. Thus the crash_notes for each
possible cpu are always available.
- The crash_prepare_elf64_headers() creates an ELF PT_NOTE per cpu.
Changing to for_each_possible_cpu() is valid as the crash_notes
pointed to by each cpu PT_NOTE are present and always valid.
Furthermore, examining a common crash processing path of:
kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer
elfcorehdr /proc/vmcore vmcore
reveals how the ELF cpu PT_NOTEs are utilized:
- Upon panic, each cpu is sent an IPI and shuts itself down, recording
its state in its crash_notes. When all cpus are shutdown, the
crash kernel is launched with a pointer to the elfcorehdr.
- The crash kernel via linux/fs/proc/vmcore.c does not examine or
use the contents of the PT_NOTEs, it exposes them via /proc/vmcore.
- The makedumpfile utility uses /proc/vmcore and reads the cpu
PT_NOTEs to craft a nr_cpus variable, which is reported in a
header but otherwise generally unused. Makedumpfile creates the
vmcore.
- The 'crash' dump analyzer does not appear to reference the cpu
PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask
symbols and directly examines those structure contents from vmcore
memory. From that information it is able to determine which cpus
are present and online, and locate the corresponding crash_notes.
Said differently, it appears that 'crash' analyzer does not rely
on the ELF PT_NOTEs for cpus; rather it obtains the information
directly via kernel symbols and the memory within the vmcore.
(There maybe other vmcore generating and analysis tools that do use
these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most
common solution.)
This change results in the benefit of having all cpus described in
the elfcorehdr, and therefore reducing the need to re-generate the
elfcorehdr on cpu changes, at the small expense of an additional
56 bytes per PT_NOTE for not-present-but-possible cpus.
On systems where kexec_file_load() syscall is utilized, all the above
is valid. On systems where kexec_load() syscall is utilized, there
may be the need for the elfcorehdr to be regenerated once. The reason
being that some archs only populate the 'present' cpus in the
/sys/devices/system/cpus entries, which the userspace 'kexec' utility
uses to generate the userspace-supplied elfcorehdr. In this situation,
one memory or cpu change will rewrite the elfcorehdr via the
crash_prepare_elf64_headers() function and now all possible cpus will
be described, just as with kexec_file_load() syscall.
Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
kernel/crash_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index dba4b75f7541..537b199a8774 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -365,7 +365,7 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
ehdr->e_phentsize = sizeof(Elf64_Phdr);
/* Prepare one phdr of type PT_NOTE for each present CPU */
- for_each_present_cpu(cpu) {
+ for_each_possible_cpu(cpu) {
phdr->p_type = PT_NOTE;
notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
phdr->p_offset = phdr->p_paddr = notes_addr;
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
The function crash_prepare_elf64_headers() generates the elfcorehdr
which describes the cpus and memory in the system for the crash kernel.
In particular, it writes out ELF PT_NOTEs for memory regions and the
cpus in the system.
With respect to the cpus, the current implementation utilizes
for_each_present_cpu() which means that as cpus are added and removed,
the elfcorehdr must again be updated to reflect the new set of cpus.
The reasoning behind the change to use for_each_possible_cpu(), is:
- At kernel boot time, all percpu crash_notes are allocated for all
possible cpus; that is, crash_notes are not allocated dynamically
when cpus are plugged/unplugged. Thus the crash_notes for each
possible cpu are always available.
- The crash_prepare_elf64_headers() creates an ELF PT_NOTE per cpu.
Changing to for_each_possible_cpu() is valid as the crash_notes
pointed to by each cpu PT_NOTE are present and always valid.
Furthermore, examining a common crash processing path of:
kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer
elfcorehdr /proc/vmcore vmcore
reveals how the ELF cpu PT_NOTEs are utilized:
- Upon panic, each cpu is sent an IPI and shuts itself down, recording
its state in its crash_notes. When all cpus are shutdown, the
crash kernel is launched with a pointer to the elfcorehdr.
- The crash kernel via linux/fs/proc/vmcore.c does not examine or
use the contents of the PT_NOTEs, it exposes them via /proc/vmcore.
- The makedumpfile utility uses /proc/vmcore and reads the cpu
PT_NOTEs to craft a nr_cpus variable, which is reported in a
header but otherwise generally unused. Makedumpfile creates the
vmcore.
- The 'crash' dump analyzer does not appear to reference the cpu
PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask
symbols and directly examines those structure contents from vmcore
memory. From that information it is able to determine which cpus
are present and online, and locate the corresponding crash_notes.
Said differently, it appears that 'crash' analyzer does not rely
on the ELF PT_NOTEs for cpus; rather it obtains the information
directly via kernel symbols and the memory within the vmcore.
(There maybe other vmcore generating and analysis tools that do use
these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most
common solution.)
This change results in the benefit of having all cpus described in
the elfcorehdr, and therefore reducing the need to re-generate the
elfcorehdr on cpu changes, at the small expense of an additional
56 bytes per PT_NOTE for not-present-but-possible cpus.
On systems where kexec_file_load() syscall is utilized, all the above
is valid. On systems where kexec_load() syscall is utilized, there
may be the need for the elfcorehdr to be regenerated once. The reason
being that some archs only populate the 'present' cpus in the
/sys/devices/system/cpus entries, which the userspace 'kexec' utility
uses to generate the userspace-supplied elfcorehdr. In this situation,
one memory or cpu change will rewrite the elfcorehdr via the
crash_prepare_elf64_headers() function and now all possible cpus will
be described, just as with kexec_file_load() syscall.
Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
kernel/crash_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index dba4b75f7541..537b199a8774 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -365,7 +365,7 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
ehdr->e_phentsize = sizeof(Elf64_Phdr);
/* Prepare one phdr of type PT_NOTE for each present CPU */
- for_each_present_cpu(cpu) {
+ for_each_possible_cpu(cpu) {
phdr->p_type = PT_NOTE;
notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
phdr->p_offset = phdr->p_paddr = notes_addr;
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 7/7] x86/crash: optimize cpu changes
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-06 16:22 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
This patch is dependent upon the patch 'crash: change
crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
for all possible cpus, thus further cpu changes to the elfcorehdr
are not needed.
This change works for kexec_file_load() and kexec_load() syscalls.
For kexec_file_load(), crash_prepare_elf64_headers() is utilized
directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
This is the kimage->file_mode term.
For kexec_load() syscall, one cpu or memory change will cause the
elfcorehdr to be updated via crash_prepare_elf64_headers() and at
that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
kimage->elfcorehdr_updated term.
This code is intentionally *NOT* hoisted into
crash_handle_hotplug_event() as it would prevent the arch-specific
handler from running for cpu changes. This would break PPC, for
example, which needs to update other information besides the
elfcorehdr, on cpu changes.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/kernel/crash.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index c9aaec9de775..82ea2b1bdc61 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
unsigned long mem, memsz;
unsigned long elfsz = 0;
+ /* As crash_prepare_elf64_headers() has already described all
+ * possible cpus, there is no need to update the elfcorehdr
+ * for additional cpu changes. This works for both kexec_load()
+ * and kexec_file_load() syscalls.
+ */
+ if ((image->file_mode || image->elfcorehdr_updated) &&
+ ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
+ (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
+ return;
+
/*
* Create the new elfcorehdr reflecting the changes to CPU and/or
* memory resources.
--
2.31.1
^ permalink raw reply related [flat|nested] 46+ messages in thread
* [PATCH v19 7/7] x86/crash: optimize cpu changes
@ 2023-03-06 16:22 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-06 16:22 UTC (permalink / raw)
To: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky,
eric.devolder
This patch is dependent upon the patch 'crash: change
crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
for all possible cpus, thus further cpu changes to the elfcorehdr
are not needed.
This change works for kexec_file_load() and kexec_load() syscalls.
For kexec_file_load(), crash_prepare_elf64_headers() is utilized
directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
This is the kimage->file_mode term.
For kexec_load() syscall, one cpu or memory change will cause the
elfcorehdr to be updated via crash_prepare_elf64_headers() and at
that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
kimage->elfcorehdr_updated term.
This code is intentionally *NOT* hoisted into
crash_handle_hotplug_event() as it would prevent the arch-specific
handler from running for cpu changes. This would break PPC, for
example, which needs to update other information besides the
elfcorehdr, on cpu changes.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/kernel/crash.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index c9aaec9de775..82ea2b1bdc61 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
unsigned long mem, memsz;
unsigned long elfsz = 0;
+ /* As crash_prepare_elf64_headers() has already described all
+ * possible cpus, there is no need to update the elfcorehdr
+ * for additional cpu changes. This works for both kexec_load()
+ * and kexec_file_load() syscalls.
+ */
+ if ((image->file_mode || image->elfcorehdr_updated) &&
+ ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
+ (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
+ return;
+
/*
* Create the new elfcorehdr reflecting the changes to CPU and/or
* memory resources.
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 46+ messages in thread
* Re: [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-07 8:48 ` Sourabh Jain
-1 siblings, 0 replies; 46+ messages in thread
From: Sourabh Jain @ 2023-03-07 8:48 UTC (permalink / raw)
To: Eric DeVolder, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
Hello Eric,
On 06/03/23 21:52, Eric DeVolder wrote:
> The function crash_prepare_elf64_headers() generates the elfcorehdr
> which describes the cpus and memory in the system for the crash kernel.
> In particular, it writes out ELF PT_NOTEs for memory regions and the
> cpus in the system.
>
> With respect to the cpus, the current implementation utilizes
> for_each_present_cpu() which means that as cpus are added and removed,
> the elfcorehdr must again be updated to reflect the new set of cpus.
>
> The reasoning behind the change to use for_each_possible_cpu(), is:
>
> - At kernel boot time, all percpu crash_notes are allocated for all
> possible cpus; that is, crash_notes are not allocated dynamically
> when cpus are plugged/unplugged. Thus the crash_notes for each
> possible cpu are always available.
>
> - The crash_prepare_elf64_headers() creates an ELF PT_NOTE per cpu.
> Changing to for_each_possible_cpu() is valid as the crash_notes
> pointed to by each cpu PT_NOTE are present and always valid.
>
> Furthermore, examining a common crash processing path of:
>
> kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer
> elfcorehdr /proc/vmcore vmcore
>
> reveals how the ELF cpu PT_NOTEs are utilized:
>
> - Upon panic, each cpu is sent an IPI and shuts itself down, recording
> its state in its crash_notes. When all cpus are shutdown, the
> crash kernel is launched with a pointer to the elfcorehdr.
>
> - The crash kernel via linux/fs/proc/vmcore.c does not examine or
> use the contents of the PT_NOTEs, it exposes them via /proc/vmcore.
>
> - The makedumpfile utility uses /proc/vmcore and reads the cpu
> PT_NOTEs to craft a nr_cpus variable, which is reported in a
> header but otherwise generally unused. Makedumpfile creates the
> vmcore.
>
> - The 'crash' dump analyzer does not appear to reference the cpu
> PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask
> symbols and directly examines those structure contents from vmcore
> memory. From that information it is able to determine which cpus
> are present and online, and locate the corresponding crash_notes.
> Said differently, it appears that 'crash' analyzer does not rely
> on the ELF PT_NOTEs for cpus; rather it obtains the information
> directly via kernel symbols and the memory within the vmcore.
>
> (There maybe other vmcore generating and analysis tools that do use
> these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most
> common solution.)
>
> This change results in the benefit of having all cpus described in
> the elfcorehdr, and therefore reducing the need to re-generate the
> elfcorehdr on cpu changes, at the small expense of an additional
> 56 bytes per PT_NOTE for not-present-but-possible cpus.
>
> On systems where kexec_file_load() syscall is utilized, all the above
> is valid. On systems where kexec_load() syscall is utilized, there
> may be the need for the elfcorehdr to be regenerated once. The reason
> being that some archs only populate the 'present' cpus in the
> /sys/devices/system/cpus entries, which the userspace 'kexec' utility
> uses to generate the userspace-supplied elfcorehdr. In this situation,
> one memory or cpu change will rewrite the elfcorehdr via the
> crash_prepare_elf64_headers() function and now all possible cpus will
> be described, just as with kexec_file_load() syscall.
>
> Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> kernel/crash_core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index dba4b75f7541..537b199a8774 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -365,7 +365,7 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
> ehdr->e_phentsize = sizeof(Elf64_Phdr);
>
> /* Prepare one phdr of type PT_NOTE for each present CPU */
We need to change this comment as well.
> - for_each_present_cpu(cpu) {
> + for_each_possible_cpu(cpu) {
- Sourabh Jain
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
@ 2023-03-07 8:48 ` Sourabh Jain
0 siblings, 0 replies; 46+ messages in thread
From: Sourabh Jain @ 2023-03-07 8:48 UTC (permalink / raw)
To: Eric DeVolder, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
Hello Eric,
On 06/03/23 21:52, Eric DeVolder wrote:
> The function crash_prepare_elf64_headers() generates the elfcorehdr
> which describes the cpus and memory in the system for the crash kernel.
> In particular, it writes out ELF PT_NOTEs for memory regions and the
> cpus in the system.
>
> With respect to the cpus, the current implementation utilizes
> for_each_present_cpu() which means that as cpus are added and removed,
> the elfcorehdr must again be updated to reflect the new set of cpus.
>
> The reasoning behind the change to use for_each_possible_cpu(), is:
>
> - At kernel boot time, all percpu crash_notes are allocated for all
> possible cpus; that is, crash_notes are not allocated dynamically
> when cpus are plugged/unplugged. Thus the crash_notes for each
> possible cpu are always available.
>
> - The crash_prepare_elf64_headers() creates an ELF PT_NOTE per cpu.
> Changing to for_each_possible_cpu() is valid as the crash_notes
> pointed to by each cpu PT_NOTE are present and always valid.
>
> Furthermore, examining a common crash processing path of:
>
> kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer
> elfcorehdr /proc/vmcore vmcore
>
> reveals how the ELF cpu PT_NOTEs are utilized:
>
> - Upon panic, each cpu is sent an IPI and shuts itself down, recording
> its state in its crash_notes. When all cpus are shutdown, the
> crash kernel is launched with a pointer to the elfcorehdr.
>
> - The crash kernel via linux/fs/proc/vmcore.c does not examine or
> use the contents of the PT_NOTEs, it exposes them via /proc/vmcore.
>
> - The makedumpfile utility uses /proc/vmcore and reads the cpu
> PT_NOTEs to craft a nr_cpus variable, which is reported in a
> header but otherwise generally unused. Makedumpfile creates the
> vmcore.
>
> - The 'crash' dump analyzer does not appear to reference the cpu
> PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask
> symbols and directly examines those structure contents from vmcore
> memory. From that information it is able to determine which cpus
> are present and online, and locate the corresponding crash_notes.
> Said differently, it appears that 'crash' analyzer does not rely
> on the ELF PT_NOTEs for cpus; rather it obtains the information
> directly via kernel symbols and the memory within the vmcore.
>
> (There maybe other vmcore generating and analysis tools that do use
> these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most
> common solution.)
>
> This change results in the benefit of having all cpus described in
> the elfcorehdr, and therefore reducing the need to re-generate the
> elfcorehdr on cpu changes, at the small expense of an additional
> 56 bytes per PT_NOTE for not-present-but-possible cpus.
>
> On systems where kexec_file_load() syscall is utilized, all the above
> is valid. On systems where kexec_load() syscall is utilized, there
> may be the need for the elfcorehdr to be regenerated once. The reason
> being that some archs only populate the 'present' cpus in the
> /sys/devices/system/cpus entries, which the userspace 'kexec' utility
> uses to generate the userspace-supplied elfcorehdr. In this situation,
> one memory or cpu change will rewrite the elfcorehdr via the
> crash_prepare_elf64_headers() function and now all possible cpus will
> be described, just as with kexec_file_load() syscall.
>
> Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> kernel/crash_core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index dba4b75f7541..537b199a8774 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -365,7 +365,7 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
> ehdr->e_phentsize = sizeof(Elf64_Phdr);
>
> /* Prepare one phdr of type PT_NOTE for each present CPU */
We need to change this comment as well.
> - for_each_present_cpu(cpu) {
> + for_each_possible_cpu(cpu) {
- Sourabh Jain
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 7/7] x86/crash: optimize cpu changes
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-07 9:00 ` Sourabh Jain
-1 siblings, 0 replies; 46+ messages in thread
From: Sourabh Jain @ 2023-03-07 9:00 UTC (permalink / raw)
To: Eric DeVolder, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 06/03/23 21:52, Eric DeVolder wrote:
> This patch is dependent upon the patch 'crash: change
> crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
> patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
> for all possible cpus, thus further cpu changes to the elfcorehdr
> are not needed.
>
> This change works for kexec_file_load() and kexec_load() syscalls.
> For kexec_file_load(), crash_prepare_elf64_headers() is utilized
> directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
> This is the kimage->file_mode term.
> For kexec_load() syscall, one cpu or memory change will cause the
> elfcorehdr to be updated via crash_prepare_elf64_headers() and at
> that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
> kimage->elfcorehdr_updated term.
>
> This code is intentionally *NOT* hoisted into
> crash_handle_hotplug_event() as it would prevent the arch-specific
> handler from running for cpu changes. This would break PPC, for
> example, which needs to update other information besides the
> elfcorehdr, on cpu changes.
>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> arch/x86/kernel/crash.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index c9aaec9de775..82ea2b1bdc61 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
> unsigned long mem, memsz;
> unsigned long elfsz = 0;
>
> + /* As crash_prepare_elf64_headers() has already described all
> + * possible cpus, there is no need to update the elfcorehdr
> + * for additional cpu changes. This works for both kexec_load()
> + * and kexec_file_load() syscalls.
> + */
> + if ((image->file_mode || image->elfcorehdr_updated) &&
> + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
> + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
> + return;
I like the idea of having elfcorehdr_updated to track elfcoredhr segment
updates.
It handles the possible CPU thing for kexec_load syscall nicely.
Thanks for incorporating the possible CPU change.
The patch series looks good to me.
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
- Sourabh Jain
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 7/7] x86/crash: optimize cpu changes
@ 2023-03-07 9:00 ` Sourabh Jain
0 siblings, 0 replies; 46+ messages in thread
From: Sourabh Jain @ 2023-03-07 9:00 UTC (permalink / raw)
To: Eric DeVolder, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 06/03/23 21:52, Eric DeVolder wrote:
> This patch is dependent upon the patch 'crash: change
> crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
> patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
> for all possible cpus, thus further cpu changes to the elfcorehdr
> are not needed.
>
> This change works for kexec_file_load() and kexec_load() syscalls.
> For kexec_file_load(), crash_prepare_elf64_headers() is utilized
> directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
> This is the kimage->file_mode term.
> For kexec_load() syscall, one cpu or memory change will cause the
> elfcorehdr to be updated via crash_prepare_elf64_headers() and at
> that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
> kimage->elfcorehdr_updated term.
>
> This code is intentionally *NOT* hoisted into
> crash_handle_hotplug_event() as it would prevent the arch-specific
> handler from running for cpu changes. This would break PPC, for
> example, which needs to update other information besides the
> elfcorehdr, on cpu changes.
>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> arch/x86/kernel/crash.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index c9aaec9de775..82ea2b1bdc61 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
> unsigned long mem, memsz;
> unsigned long elfsz = 0;
>
> + /* As crash_prepare_elf64_headers() has already described all
> + * possible cpus, there is no need to update the elfcorehdr
> + * for additional cpu changes. This works for both kexec_load()
> + * and kexec_file_load() syscalls.
> + */
> + if ((image->file_mode || image->elfcorehdr_updated) &&
> + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
> + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
> + return;
I like the idea of having elfcorehdr_updated to track elfcoredhr segment
updates.
It handles the possible CPU thing for kexec_load syscall nicely.
Thanks for incorporating the possible CPU change.
The patch series looks good to me.
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
- Sourabh Jain
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 5/7] x86/crash: add x86 crash hotplug support
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-08 3:08 ` Sourabh Jain
-1 siblings, 0 replies; 46+ messages in thread
From: Sourabh Jain @ 2023-03-08 3:08 UTC (permalink / raw)
To: Eric DeVolder, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 06/03/23 21:52, Eric DeVolder wrote:
> When CPU or memory is hot un/plugged, or off/onlined, the crash
> elfcorehdr, which describes the CPUs and memory in the system,
> must also be updated.
>
> The segment containing the elfcorehdr is identified at run-time
> in crash_core:crash_handle_hotplug_event(), which works for both
> the kexec_load() and kexec_file_load() syscalls. A new elfcorehdr
> is generated from the available CPUs and memory into a buffer,
> and then installed over the top of the existing elfcorehdr.
>
> In the patch 'kexec: exclude elfcorehdr from the segment digest'
> the need to update purgatory due to the change in elfcorehdr was
> eliminated. As a result, no changes to purgatory or boot_params
> (as the elfcorehdr= kernel command line parameter pointer
> remains unchanged and correct) are needed, just elfcorehdr.
>
> To accommodate a growing number of resources via hotplug, the
> elfcorehdr segment must be sufficiently large enough to accommodate
> changes, see the CRASH_MAX_MEMORY_RANGES description. This is used
> only on the kexec_file_load() syscall; for kexec_load() userspace
> will need to size the segment similarly.
>
> To accommodate kexec_load() syscall in the absence of
> kexec_file_load() syscall support, and with CONFIG_CRASH_HOTPLUG
> enabled, it is necessary to move prepare_elf_headers() and
> dependents outside of CONFIG_KEXEC_FILE.
>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> arch/x86/Kconfig | 13 ++++
> arch/x86/include/asm/kexec.h | 15 +++++
> arch/x86/kernel/crash.c | 119 ++++++++++++++++++++++++++++++++---
> 3 files changed, 140 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 3604074a878b..2ca5e19b8f19 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2119,6 +2119,19 @@ config CRASH_DUMP
> (CONFIG_RELOCATABLE=y).
> For more details see Documentation/admin-guide/kdump/kdump.rst
>
> +config CRASH_HOTPLUG
> + bool "Update the crash elfcorehdr on system configuration changes"
> + default n
How about enabling this by default?
- Sourabh
> + depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG)
> + help
> + Enable direct update to the crash elfcorehdr (which contains
> + the list of CPUs and memory regions to be dumped upon a crash)
> + in response to hot plug/unplug or online/offline of CPUs or
> + memory. This is a much more advanced approach than userspace
> + attempting that.
> +
> + If unsure, say Y.
> +
> config KEXEC_JUMP
> bool "kexec jump"
> depends on KEXEC && HIBERNATION
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index a3760ca796aa..1bc852ce347d 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -212,6 +212,21 @@ typedef void crash_vmclear_fn(void);
> extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
> extern void kdump_nmi_shootdown_cpus(void);
>
> +#ifdef CONFIG_CRASH_HOTPLUG
> +void arch_crash_handle_hotplug_event(struct kimage *image);
> +#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
> +
> +#ifdef CONFIG_HOTPLUG_CPU
> +static inline int crash_hotplug_cpu_support(void) { return 1; }
> +#define crash_hotplug_cpu_support crash_hotplug_cpu_support
> +#endif
> +
> +#ifdef CONFIG_MEMORY_HOTPLUG
> +static inline int crash_hotplug_memory_support(void) { return 1; }
> +#define crash_hotplug_memory_support crash_hotplug_memory_support
> +#endif
> +#endif
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_X86_KEXEC_H */
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 305514431f26..c9aaec9de775 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -42,6 +42,21 @@
> #include <asm/crash.h>
> #include <asm/cmdline.h>
>
> +/*
> + * For the kexec_file_load() syscall path, specify the maximum number of
> + * memory regions that the elfcorehdr buffer/segment can accommodate.
> + * These regions are obtained via walk_system_ram_res(); eg. the
> + * 'System RAM' entries in /proc/iomem.
> + * This value is combined with NR_CPUS_DEFAULT and multiplied by
> + * sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/
> + * segment size.
> + * The value 8192, for example, covers a (sparsely populated) 1TiB system
> + * consisting of 128MiB memblocks, while resulting in an elfcorehdr
> + * memory buffer/segment size under 1MiB. This represents a sane choice
> + * to accommodate both baremetal and virtual machine configurations.
> + */
> +#define CRASH_MAX_MEMORY_RANGES 8192
> +
> /* Used while preparing memory map entries for second kernel */
> struct crash_memmap_data {
> struct boot_params *params;
> @@ -173,8 +188,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
> crash_save_cpu(regs, safe_smp_processor_id());
> }
>
> -#ifdef CONFIG_KEXEC_FILE
> -
> static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
> {
> unsigned int *nr_ranges = arg;
> @@ -246,7 +259,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>
> /* Prepare elf headers. Return addr and size */
> static int prepare_elf_headers(struct kimage *image, void **addr,
> - unsigned long *sz)
> + unsigned long *sz, unsigned long *nr_mem_ranges)
> {
> struct crash_mem *cmem;
> int ret;
> @@ -264,6 +277,9 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
> if (ret)
> goto out;
>
> + /* Return the computed number of memory ranges, for hotplug usage */
> + *nr_mem_ranges = cmem->nr_ranges;
> +
> /* By default prepare 64bit headers */
> ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
>
> @@ -272,6 +288,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
> return ret;
> }
>
> +#ifdef CONFIG_KEXEC_FILE
> static int add_e820_entry(struct boot_params *params, struct e820_entry *entry)
> {
> unsigned int nr_e820_entries;
> @@ -386,18 +403,42 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
> int crash_load_segments(struct kimage *image)
> {
> int ret;
> + unsigned long pnum = 0;
> struct kexec_buf kbuf = { .image = image, .buf_min = 0,
> .buf_max = ULONG_MAX, .top_down = false };
>
> /* Prepare elf headers and add a segment */
> - ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
> + ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz, &pnum);
> if (ret)
> return ret;
>
> - image->elf_headers = kbuf.buffer;
> - image->elf_headers_sz = kbuf.bufsz;
> + image->elf_headers = kbuf.buffer;
> + image->elf_headers_sz = kbuf.bufsz;
> + kbuf.memsz = kbuf.bufsz;
> +
> +#ifdef CONFIG_CRASH_HOTPLUG
> + /*
> + * Ensure the elfcorehdr segment large enough for hotplug changes.
> + * Account for VMCOREINFO and kernel_map and maximum CPUs.
> + */
> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
> + pnum = 2 + CONFIG_NR_CPUS_DEFAULT + CRASH_MAX_MEMORY_RANGES;
> + else
> + pnum += 2 + CONFIG_NR_CPUS_DEFAULT;
> +
> + if (pnum < (unsigned long)PN_XNUM) {
> + kbuf.memsz = pnum * sizeof(Elf64_Phdr);
> + kbuf.memsz += sizeof(Elf64_Ehdr);
> +
> + image->elfcorehdr_index = image->nr_segments;
> +
> + /* Mark as usable to crash kernel, else crash kernel fails on boot */
> + image->elf_headers_sz = kbuf.memsz;
> + } else {
> + pr_err("number of Phdrs %lu exceeds max\n", pnum);
> + }
> +#endif
>
> - kbuf.memsz = kbuf.bufsz;
> kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
> kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> ret = kexec_add_buffer(&kbuf);
> @@ -410,3 +451,67 @@ int crash_load_segments(struct kimage *image)
> return ret;
> }
> #endif /* CONFIG_KEXEC_FILE */
> +
> +#ifdef CONFIG_CRASH_HOTPLUG
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) "crash hp: " fmt
> +
> +/**
> + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
> + * @image: the active struct kimage
> + *
> + * The new elfcorehdr is prepared in a kernel buffer, and then it is
> + * written on top of the existing/old elfcorehdr.
> + */
> +void arch_crash_handle_hotplug_event(struct kimage *image)
> +{
> + void *elfbuf = NULL, *old_elfcorehdr;
> + unsigned long nr_mem_ranges;
> + unsigned long mem, memsz;
> + unsigned long elfsz = 0;
> +
> + /*
> + * Create the new elfcorehdr reflecting the changes to CPU and/or
> + * memory resources.
> + */
> + if (prepare_elf_headers(image, &elfbuf, &elfsz, &nr_mem_ranges)) {
> + pr_err("unable to prepare elfcore headers");
> + goto out;
> + }
> +
> + /*
> + * Obtain address and size of the elfcorehdr segment, and
> + * check it against the new elfcorehdr buffer.
> + */
> + mem = image->segment[image->elfcorehdr_index].mem;
> + memsz = image->segment[image->elfcorehdr_index].memsz;
> + if (elfsz > memsz) {
> + pr_err("update elfcorehdr elfsz %lu > memsz %lu",
> + elfsz, memsz);
> + goto out;
> + }
> +
> + /*
> + * Copy new elfcorehdr over the old elfcorehdr at destination.
> + */
> + old_elfcorehdr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> + if (!old_elfcorehdr) {
> + pr_err("updating elfcorehdr failed\n");
> + goto out;
> + }
> +
> + /*
> + * Temporarily invalidate the crash image while the
> + * elfcorehdr is updated.
> + */
> + xchg(&kexec_crash_image, NULL);
> + memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz);
> + xchg(&kexec_crash_image, image);
> + kunmap_local(old_elfcorehdr);
> + pr_debug("updated elfcorehdr\n");
> +
> +out:
> + vfree(elfbuf);
> +}
> +#endif
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 5/7] x86/crash: add x86 crash hotplug support
@ 2023-03-08 3:08 ` Sourabh Jain
0 siblings, 0 replies; 46+ messages in thread
From: Sourabh Jain @ 2023-03-08 3:08 UTC (permalink / raw)
To: Eric DeVolder, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 06/03/23 21:52, Eric DeVolder wrote:
> When CPU or memory is hot un/plugged, or off/onlined, the crash
> elfcorehdr, which describes the CPUs and memory in the system,
> must also be updated.
>
> The segment containing the elfcorehdr is identified at run-time
> in crash_core:crash_handle_hotplug_event(), which works for both
> the kexec_load() and kexec_file_load() syscalls. A new elfcorehdr
> is generated from the available CPUs and memory into a buffer,
> and then installed over the top of the existing elfcorehdr.
>
> In the patch 'kexec: exclude elfcorehdr from the segment digest'
> the need to update purgatory due to the change in elfcorehdr was
> eliminated. As a result, no changes to purgatory or boot_params
> (as the elfcorehdr= kernel command line parameter pointer
> remains unchanged and correct) are needed, just elfcorehdr.
>
> To accommodate a growing number of resources via hotplug, the
> elfcorehdr segment must be sufficiently large enough to accommodate
> changes, see the CRASH_MAX_MEMORY_RANGES description. This is used
> only on the kexec_file_load() syscall; for kexec_load() userspace
> will need to size the segment similarly.
>
> To accommodate kexec_load() syscall in the absence of
> kexec_file_load() syscall support, and with CONFIG_CRASH_HOTPLUG
> enabled, it is necessary to move prepare_elf_headers() and
> dependents outside of CONFIG_KEXEC_FILE.
>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> arch/x86/Kconfig | 13 ++++
> arch/x86/include/asm/kexec.h | 15 +++++
> arch/x86/kernel/crash.c | 119 ++++++++++++++++++++++++++++++++---
> 3 files changed, 140 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 3604074a878b..2ca5e19b8f19 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2119,6 +2119,19 @@ config CRASH_DUMP
> (CONFIG_RELOCATABLE=y).
> For more details see Documentation/admin-guide/kdump/kdump.rst
>
> +config CRASH_HOTPLUG
> + bool "Update the crash elfcorehdr on system configuration changes"
> + default n
How about enabling this by default?
- Sourabh
> + depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG)
> + help
> + Enable direct update to the crash elfcorehdr (which contains
> + the list of CPUs and memory regions to be dumped upon a crash)
> + in response to hot plug/unplug or online/offline of CPUs or
> + memory. This is a much more advanced approach than userspace
> + attempting that.
> +
> + If unsure, say Y.
> +
> config KEXEC_JUMP
> bool "kexec jump"
> depends on KEXEC && HIBERNATION
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index a3760ca796aa..1bc852ce347d 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -212,6 +212,21 @@ typedef void crash_vmclear_fn(void);
> extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
> extern void kdump_nmi_shootdown_cpus(void);
>
> +#ifdef CONFIG_CRASH_HOTPLUG
> +void arch_crash_handle_hotplug_event(struct kimage *image);
> +#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
> +
> +#ifdef CONFIG_HOTPLUG_CPU
> +static inline int crash_hotplug_cpu_support(void) { return 1; }
> +#define crash_hotplug_cpu_support crash_hotplug_cpu_support
> +#endif
> +
> +#ifdef CONFIG_MEMORY_HOTPLUG
> +static inline int crash_hotplug_memory_support(void) { return 1; }
> +#define crash_hotplug_memory_support crash_hotplug_memory_support
> +#endif
> +#endif
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_X86_KEXEC_H */
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 305514431f26..c9aaec9de775 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -42,6 +42,21 @@
> #include <asm/crash.h>
> #include <asm/cmdline.h>
>
> +/*
> + * For the kexec_file_load() syscall path, specify the maximum number of
> + * memory regions that the elfcorehdr buffer/segment can accommodate.
> + * These regions are obtained via walk_system_ram_res(); eg. the
> + * 'System RAM' entries in /proc/iomem.
> + * This value is combined with NR_CPUS_DEFAULT and multiplied by
> + * sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/
> + * segment size.
> + * The value 8192, for example, covers a (sparsely populated) 1TiB system
> + * consisting of 128MiB memblocks, while resulting in an elfcorehdr
> + * memory buffer/segment size under 1MiB. This represents a sane choice
> + * to accommodate both baremetal and virtual machine configurations.
> + */
> +#define CRASH_MAX_MEMORY_RANGES 8192
> +
> /* Used while preparing memory map entries for second kernel */
> struct crash_memmap_data {
> struct boot_params *params;
> @@ -173,8 +188,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
> crash_save_cpu(regs, safe_smp_processor_id());
> }
>
> -#ifdef CONFIG_KEXEC_FILE
> -
> static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
> {
> unsigned int *nr_ranges = arg;
> @@ -246,7 +259,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>
> /* Prepare elf headers. Return addr and size */
> static int prepare_elf_headers(struct kimage *image, void **addr,
> - unsigned long *sz)
> + unsigned long *sz, unsigned long *nr_mem_ranges)
> {
> struct crash_mem *cmem;
> int ret;
> @@ -264,6 +277,9 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
> if (ret)
> goto out;
>
> + /* Return the computed number of memory ranges, for hotplug usage */
> + *nr_mem_ranges = cmem->nr_ranges;
> +
> /* By default prepare 64bit headers */
> ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
>
> @@ -272,6 +288,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
> return ret;
> }
>
> +#ifdef CONFIG_KEXEC_FILE
> static int add_e820_entry(struct boot_params *params, struct e820_entry *entry)
> {
> unsigned int nr_e820_entries;
> @@ -386,18 +403,42 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
> int crash_load_segments(struct kimage *image)
> {
> int ret;
> + unsigned long pnum = 0;
> struct kexec_buf kbuf = { .image = image, .buf_min = 0,
> .buf_max = ULONG_MAX, .top_down = false };
>
> /* Prepare elf headers and add a segment */
> - ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
> + ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz, &pnum);
> if (ret)
> return ret;
>
> - image->elf_headers = kbuf.buffer;
> - image->elf_headers_sz = kbuf.bufsz;
> + image->elf_headers = kbuf.buffer;
> + image->elf_headers_sz = kbuf.bufsz;
> + kbuf.memsz = kbuf.bufsz;
> +
> +#ifdef CONFIG_CRASH_HOTPLUG
> + /*
> + * Ensure the elfcorehdr segment large enough for hotplug changes.
> + * Account for VMCOREINFO and kernel_map and maximum CPUs.
> + */
> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
> + pnum = 2 + CONFIG_NR_CPUS_DEFAULT + CRASH_MAX_MEMORY_RANGES;
> + else
> + pnum += 2 + CONFIG_NR_CPUS_DEFAULT;
> +
> + if (pnum < (unsigned long)PN_XNUM) {
> + kbuf.memsz = pnum * sizeof(Elf64_Phdr);
> + kbuf.memsz += sizeof(Elf64_Ehdr);
> +
> + image->elfcorehdr_index = image->nr_segments;
> +
> + /* Mark as usable to crash kernel, else crash kernel fails on boot */
> + image->elf_headers_sz = kbuf.memsz;
> + } else {
> + pr_err("number of Phdrs %lu exceeds max\n", pnum);
> + }
> +#endif
>
> - kbuf.memsz = kbuf.bufsz;
> kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
> kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> ret = kexec_add_buffer(&kbuf);
> @@ -410,3 +451,67 @@ int crash_load_segments(struct kimage *image)
> return ret;
> }
> #endif /* CONFIG_KEXEC_FILE */
> +
> +#ifdef CONFIG_CRASH_HOTPLUG
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) "crash hp: " fmt
> +
> +/**
> + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
> + * @image: the active struct kimage
> + *
> + * The new elfcorehdr is prepared in a kernel buffer, and then it is
> + * written on top of the existing/old elfcorehdr.
> + */
> +void arch_crash_handle_hotplug_event(struct kimage *image)
> +{
> + void *elfbuf = NULL, *old_elfcorehdr;
> + unsigned long nr_mem_ranges;
> + unsigned long mem, memsz;
> + unsigned long elfsz = 0;
> +
> + /*
> + * Create the new elfcorehdr reflecting the changes to CPU and/or
> + * memory resources.
> + */
> + if (prepare_elf_headers(image, &elfbuf, &elfsz, &nr_mem_ranges)) {
> + pr_err("unable to prepare elfcore headers");
> + goto out;
> + }
> +
> + /*
> + * Obtain address and size of the elfcorehdr segment, and
> + * check it against the new elfcorehdr buffer.
> + */
> + mem = image->segment[image->elfcorehdr_index].mem;
> + memsz = image->segment[image->elfcorehdr_index].memsz;
> + if (elfsz > memsz) {
> + pr_err("update elfcorehdr elfsz %lu > memsz %lu",
> + elfsz, memsz);
> + goto out;
> + }
> +
> + /*
> + * Copy new elfcorehdr over the old elfcorehdr at destination.
> + */
> + old_elfcorehdr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> + if (!old_elfcorehdr) {
> + pr_err("updating elfcorehdr failed\n");
> + goto out;
> + }
> +
> + /*
> + * Temporarily invalidate the crash image while the
> + * elfcorehdr is updated.
> + */
> + xchg(&kexec_crash_image, NULL);
> + memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz);
> + xchg(&kexec_crash_image, image);
> + kunmap_local(old_elfcorehdr);
> + pr_debug("updated elfcorehdr\n");
> +
> +out:
> + vfree(elfbuf);
> +}
> +#endif
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kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-14 10:43 ` Baoquan He
-1 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-14 10:43 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/06/23 at 11:22am, Eric DeVolder wrote:
......
> +#ifdef CONFIG_CRASH_HOTPLUG
> +#undef pr_fmt
> +#define pr_fmt(fmt) "crash hp: " fmt
> +/*
> + * To accurately reflect hot un/plug changes of cpu and memory resources
> + * (including onling and offlining of those resources), the elfcorehdr
> + * (which is passed to the crash kernel via the elfcorehdr= parameter)
> + * must be updated with the new list of CPUs and memories.
> + *
> + * In order to make changes to elfcorehdr, two conditions are needed:
> + * First, the segment containing the elfcorehdr must be large enough
> + * to permit a growing number of resources; the elfcorehdr memory size
> + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
> + * Second, purgatory must explicitly exclude the elfcorehdr from the
> + * list of segments it checks (since the elfcorehdr changes and thus
> + * would require an update to purgatory itself to update the digest).
> + */
> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> +{
> + /* Obtain lock while changing crash information */
> + if (kexec_trylock()) {
> +
> + /* Check kdump is loaded */
> + if (kexec_crash_image) {
If the above check failed, I would directly return or jump out becuase
one indentation can be reduced.
> + struct kimage *image = kexec_crash_image;
> +
> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> + else
> + pr_debug("hp_action %u\n", hp_action);
> +
> + /*
> + * When the struct kimage is allocated, the elfcorehdr_index
> + * is set to -1. Find the segment containing the elfcorehdr,
> + * if not already found. This works for both the kexec_load
> + * and kexec_file_load paths.
> + */
> + if (image->elfcorehdr_index < 0) {
> + unsigned long mem;
> + unsigned char *ptr;
> + unsigned int n;
> +
> + for (n = 0; n < image->nr_segments; n++) {
> + mem = image->segment[n].mem;
> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> + if (ptr) {
> + /* The segment containing elfcorehdr */
> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> + image->elfcorehdr_index = (int)n;
> + }
> + kunmap_local(ptr);
> + }
> + }
> + }
> +
> + if (image->elfcorehdr_index < 0) {
> + pr_err("unable to locate elfcorehdr segment");
> + goto out;
> + }
> +
> + /* Needed in order for the segments to be updated */
> + arch_kexec_unprotect_crashkres();
> +
> + /* Differentiate between normal load and hotplug update */
> + image->hp_action = hp_action;
> +
> + /* Now invoke arch-specific update handler */
> + arch_crash_handle_hotplug_event(image);
> +
> + /* No longer handling a hotplug event */
> + image->hp_action = KEXEC_CRASH_HP_NONE;
> + image->elfcorehdr_updated = true;
> +
> + /* Change back to read-only */
> + arch_kexec_protect_crashkres();
> + }
> +
> +out:
> + /* Release lock now that update complete */
> + kexec_unlock();
> + }
> +}
> +
> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
> +{
> + switch (val) {
> + case MEM_ONLINE:
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
> + KEXEC_CRASH_HP_INVALID_CPU);
> + break;
> +
> + case MEM_OFFLINE:
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
> + KEXEC_CRASH_HP_INVALID_CPU);
> + break;
> + }
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block crash_memhp_nb = {
> + .notifier_call = crash_memhp_notifier,
> + .priority = 0
> +};
> +
Because for_each_possible_cpu() is taken in
crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
hotplug or doesn't do anything with this patchset. This cpu part in
infrastructure is only for the later powerpc usage, right?
> +static int crash_cpuhp_online(unsigned int cpu)
> +{
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
> + return 0;
> +}
> +
> +static int crash_cpuhp_offline(unsigned int cpu)
> +{
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
> + return 0;
> +}
> +
> +static int __init crash_hotplug_init(void)
> +{
> + int result = 0;
> +
> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
> + register_memory_notifier(&crash_memhp_nb);
> +
> + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
> + result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
> + "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
> + }
> +
> + return result;
> +}
> +
> +subsys_initcall(crash_hotplug_init);
> +#endif
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 969e8f52f7da..f2f9d41ce5df 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -276,6 +276,11 @@ struct kimage *do_kimage_alloc_init(void)
> /* Initialize the list of unusable pages */
> INIT_LIST_HEAD(&image->unusable_pages);
>
> +#ifdef CONFIG_CRASH_HOTPLUG
> + image->elfcorehdr_index = -1;
> + image->elfcorehdr_updated = false;
> +#endif
> +
> return image;
> }
>
> --
> 2.31.1
>
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-14 10:43 ` Baoquan He
0 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-14 10:43 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/06/23 at 11:22am, Eric DeVolder wrote:
......
> +#ifdef CONFIG_CRASH_HOTPLUG
> +#undef pr_fmt
> +#define pr_fmt(fmt) "crash hp: " fmt
> +/*
> + * To accurately reflect hot un/plug changes of cpu and memory resources
> + * (including onling and offlining of those resources), the elfcorehdr
> + * (which is passed to the crash kernel via the elfcorehdr= parameter)
> + * must be updated with the new list of CPUs and memories.
> + *
> + * In order to make changes to elfcorehdr, two conditions are needed:
> + * First, the segment containing the elfcorehdr must be large enough
> + * to permit a growing number of resources; the elfcorehdr memory size
> + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
> + * Second, purgatory must explicitly exclude the elfcorehdr from the
> + * list of segments it checks (since the elfcorehdr changes and thus
> + * would require an update to purgatory itself to update the digest).
> + */
> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> +{
> + /* Obtain lock while changing crash information */
> + if (kexec_trylock()) {
> +
> + /* Check kdump is loaded */
> + if (kexec_crash_image) {
If the above check failed, I would directly return or jump out becuase
one indentation can be reduced.
> + struct kimage *image = kexec_crash_image;
> +
> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> + else
> + pr_debug("hp_action %u\n", hp_action);
> +
> + /*
> + * When the struct kimage is allocated, the elfcorehdr_index
> + * is set to -1. Find the segment containing the elfcorehdr,
> + * if not already found. This works for both the kexec_load
> + * and kexec_file_load paths.
> + */
> + if (image->elfcorehdr_index < 0) {
> + unsigned long mem;
> + unsigned char *ptr;
> + unsigned int n;
> +
> + for (n = 0; n < image->nr_segments; n++) {
> + mem = image->segment[n].mem;
> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> + if (ptr) {
> + /* The segment containing elfcorehdr */
> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> + image->elfcorehdr_index = (int)n;
> + }
> + kunmap_local(ptr);
> + }
> + }
> + }
> +
> + if (image->elfcorehdr_index < 0) {
> + pr_err("unable to locate elfcorehdr segment");
> + goto out;
> + }
> +
> + /* Needed in order for the segments to be updated */
> + arch_kexec_unprotect_crashkres();
> +
> + /* Differentiate between normal load and hotplug update */
> + image->hp_action = hp_action;
> +
> + /* Now invoke arch-specific update handler */
> + arch_crash_handle_hotplug_event(image);
> +
> + /* No longer handling a hotplug event */
> + image->hp_action = KEXEC_CRASH_HP_NONE;
> + image->elfcorehdr_updated = true;
> +
> + /* Change back to read-only */
> + arch_kexec_protect_crashkres();
> + }
> +
> +out:
> + /* Release lock now that update complete */
> + kexec_unlock();
> + }
> +}
> +
> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
> +{
> + switch (val) {
> + case MEM_ONLINE:
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
> + KEXEC_CRASH_HP_INVALID_CPU);
> + break;
> +
> + case MEM_OFFLINE:
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
> + KEXEC_CRASH_HP_INVALID_CPU);
> + break;
> + }
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block crash_memhp_nb = {
> + .notifier_call = crash_memhp_notifier,
> + .priority = 0
> +};
> +
Because for_each_possible_cpu() is taken in
crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
hotplug or doesn't do anything with this patchset. This cpu part in
infrastructure is only for the later powerpc usage, right?
> +static int crash_cpuhp_online(unsigned int cpu)
> +{
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
> + return 0;
> +}
> +
> +static int crash_cpuhp_offline(unsigned int cpu)
> +{
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
> + return 0;
> +}
> +
> +static int __init crash_hotplug_init(void)
> +{
> + int result = 0;
> +
> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
> + register_memory_notifier(&crash_memhp_nb);
> +
> + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
> + result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
> + "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
> + }
> +
> + return result;
> +}
> +
> +subsys_initcall(crash_hotplug_init);
> +#endif
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 969e8f52f7da..f2f9d41ce5df 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -276,6 +276,11 @@ struct kimage *do_kimage_alloc_init(void)
> /* Initialize the list of unusable pages */
> INIT_LIST_HEAD(&image->unusable_pages);
>
> +#ifdef CONFIG_CRASH_HOTPLUG
> + image->elfcorehdr_index = -1;
> + image->elfcorehdr_updated = false;
> +#endif
> +
> return image;
> }
>
> --
> 2.31.1
>
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-14 10:43 ` Baoquan He
@ 2023-03-14 13:28 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-14 13:28 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/14/23 05:43, Baoquan He wrote:
> On 03/06/23 at 11:22am, Eric DeVolder wrote:
> ......
>> +#ifdef CONFIG_CRASH_HOTPLUG
>> +#undef pr_fmt
>> +#define pr_fmt(fmt) "crash hp: " fmt
>> +/*
>> + * To accurately reflect hot un/plug changes of cpu and memory resources
>> + * (including onling and offlining of those resources), the elfcorehdr
>> + * (which is passed to the crash kernel via the elfcorehdr= parameter)
>> + * must be updated with the new list of CPUs and memories.
>> + *
>> + * In order to make changes to elfcorehdr, two conditions are needed:
>> + * First, the segment containing the elfcorehdr must be large enough
>> + * to permit a growing number of resources; the elfcorehdr memory size
>> + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
>> + * Second, purgatory must explicitly exclude the elfcorehdr from the
>> + * list of segments it checks (since the elfcorehdr changes and thus
>> + * would require an update to purgatory itself to update the digest).
>> + */
>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>> +{
>> + /* Obtain lock while changing crash information */
>> + if (kexec_trylock()) {
>> +
>> + /* Check kdump is loaded */
>> + if (kexec_crash_image) {
>
> If the above check failed, I would directly return or jump out becuase
> one indentation can be reduced.
Baoquan, ok, I'll change that in next version.
>
>> + struct kimage *image = kexec_crash_image;
>> +
>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>> + else
>> + pr_debug("hp_action %u\n", hp_action);
>> +
>> + /*
>> + * When the struct kimage is allocated, the elfcorehdr_index
>> + * is set to -1. Find the segment containing the elfcorehdr,
>> + * if not already found. This works for both the kexec_load
>> + * and kexec_file_load paths.
>> + */
>> + if (image->elfcorehdr_index < 0) {
>> + unsigned long mem;
>> + unsigned char *ptr;
>> + unsigned int n;
>> +
>> + for (n = 0; n < image->nr_segments; n++) {
>> + mem = image->segment[n].mem;
>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>> + if (ptr) {
>> + /* The segment containing elfcorehdr */
>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>> + image->elfcorehdr_index = (int)n;
>> + }
>> + kunmap_local(ptr);
>> + }
>> + }
>> + }
>> +
>> + if (image->elfcorehdr_index < 0) {
>> + pr_err("unable to locate elfcorehdr segment");
>> + goto out;
>> + }
>> +
>> + /* Needed in order for the segments to be updated */
>> + arch_kexec_unprotect_crashkres();
>> +
>> + /* Differentiate between normal load and hotplug update */
>> + image->hp_action = hp_action;
>> +
>> + /* Now invoke arch-specific update handler */
>> + arch_crash_handle_hotplug_event(image);
>> +
>> + /* No longer handling a hotplug event */
>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>> + image->elfcorehdr_updated = true;
>> +
>> + /* Change back to read-only */
>> + arch_kexec_protect_crashkres();
>> + }
>> +
>> +out:
>> + /* Release lock now that update complete */
>> + kexec_unlock();
>> + }
>> +}
>> +
>> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
>> +{
>> + switch (val) {
>> + case MEM_ONLINE:
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
>> + KEXEC_CRASH_HP_INVALID_CPU);
>> + break;
>> +
>> + case MEM_OFFLINE:
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
>> + KEXEC_CRASH_HP_INVALID_CPU);
>> + break;
>> + }
>> + return NOTIFY_OK;
>> +}
>> +
>> +static struct notifier_block crash_memhp_nb = {
>> + .notifier_call = crash_memhp_notifier,
>> + .priority = 0
>> +};
>> +
>
> Because for_each_possible_cpu() is taken in
> crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
> hotplug or doesn't do anything with this patchset. This cpu part in
> infrastructure is only for the later powerpc usage, right?
That is true, yes.
>
>> +static int crash_cpuhp_online(unsigned int cpu)
>> +{
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
>> + return 0;
>> +}
>> +
>> +static int crash_cpuhp_offline(unsigned int cpu)
>> +{
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
>> + return 0;
>> +}
>> +
>> +static int __init crash_hotplug_init(void)
>> +{
>> + int result = 0;
>> +
>> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
>> + register_memory_notifier(&crash_memhp_nb);
>> +
>> + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
>> + result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
>> + "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
>> + }
>> +
>> + return result;
>> +}
>> +
>> +subsys_initcall(crash_hotplug_init);
>> +#endif
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 969e8f52f7da..f2f9d41ce5df 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -276,6 +276,11 @@ struct kimage *do_kimage_alloc_init(void)
>> /* Initialize the list of unusable pages */
>> INIT_LIST_HEAD(&image->unusable_pages);
>>
>> +#ifdef CONFIG_CRASH_HOTPLUG
>> + image->elfcorehdr_index = -1;
>> + image->elfcorehdr_updated = false;
>> +#endif
>> +
>> return image;
>> }
>>
>> --
>> 2.31.1
>>
>
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-14 13:28 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-14 13:28 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/14/23 05:43, Baoquan He wrote:
> On 03/06/23 at 11:22am, Eric DeVolder wrote:
> ......
>> +#ifdef CONFIG_CRASH_HOTPLUG
>> +#undef pr_fmt
>> +#define pr_fmt(fmt) "crash hp: " fmt
>> +/*
>> + * To accurately reflect hot un/plug changes of cpu and memory resources
>> + * (including onling and offlining of those resources), the elfcorehdr
>> + * (which is passed to the crash kernel via the elfcorehdr= parameter)
>> + * must be updated with the new list of CPUs and memories.
>> + *
>> + * In order to make changes to elfcorehdr, two conditions are needed:
>> + * First, the segment containing the elfcorehdr must be large enough
>> + * to permit a growing number of resources; the elfcorehdr memory size
>> + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES.
>> + * Second, purgatory must explicitly exclude the elfcorehdr from the
>> + * list of segments it checks (since the elfcorehdr changes and thus
>> + * would require an update to purgatory itself to update the digest).
>> + */
>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>> +{
>> + /* Obtain lock while changing crash information */
>> + if (kexec_trylock()) {
>> +
>> + /* Check kdump is loaded */
>> + if (kexec_crash_image) {
>
> If the above check failed, I would directly return or jump out becuase
> one indentation can be reduced.
Baoquan, ok, I'll change that in next version.
>
>> + struct kimage *image = kexec_crash_image;
>> +
>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>> + else
>> + pr_debug("hp_action %u\n", hp_action);
>> +
>> + /*
>> + * When the struct kimage is allocated, the elfcorehdr_index
>> + * is set to -1. Find the segment containing the elfcorehdr,
>> + * if not already found. This works for both the kexec_load
>> + * and kexec_file_load paths.
>> + */
>> + if (image->elfcorehdr_index < 0) {
>> + unsigned long mem;
>> + unsigned char *ptr;
>> + unsigned int n;
>> +
>> + for (n = 0; n < image->nr_segments; n++) {
>> + mem = image->segment[n].mem;
>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>> + if (ptr) {
>> + /* The segment containing elfcorehdr */
>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>> + image->elfcorehdr_index = (int)n;
>> + }
>> + kunmap_local(ptr);
>> + }
>> + }
>> + }
>> +
>> + if (image->elfcorehdr_index < 0) {
>> + pr_err("unable to locate elfcorehdr segment");
>> + goto out;
>> + }
>> +
>> + /* Needed in order for the segments to be updated */
>> + arch_kexec_unprotect_crashkres();
>> +
>> + /* Differentiate between normal load and hotplug update */
>> + image->hp_action = hp_action;
>> +
>> + /* Now invoke arch-specific update handler */
>> + arch_crash_handle_hotplug_event(image);
>> +
>> + /* No longer handling a hotplug event */
>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>> + image->elfcorehdr_updated = true;
>> +
>> + /* Change back to read-only */
>> + arch_kexec_protect_crashkres();
>> + }
>> +
>> +out:
>> + /* Release lock now that update complete */
>> + kexec_unlock();
>> + }
>> +}
>> +
>> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
>> +{
>> + switch (val) {
>> + case MEM_ONLINE:
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
>> + KEXEC_CRASH_HP_INVALID_CPU);
>> + break;
>> +
>> + case MEM_OFFLINE:
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
>> + KEXEC_CRASH_HP_INVALID_CPU);
>> + break;
>> + }
>> + return NOTIFY_OK;
>> +}
>> +
>> +static struct notifier_block crash_memhp_nb = {
>> + .notifier_call = crash_memhp_notifier,
>> + .priority = 0
>> +};
>> +
>
> Because for_each_possible_cpu() is taken in
> crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
> hotplug or doesn't do anything with this patchset. This cpu part in
> infrastructure is only for the later powerpc usage, right?
That is true, yes.
>
>> +static int crash_cpuhp_online(unsigned int cpu)
>> +{
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
>> + return 0;
>> +}
>> +
>> +static int crash_cpuhp_offline(unsigned int cpu)
>> +{
>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
>> + return 0;
>> +}
>> +
>> +static int __init crash_hotplug_init(void)
>> +{
>> + int result = 0;
>> +
>> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
>> + register_memory_notifier(&crash_memhp_nb);
>> +
>> + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
>> + result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
>> + "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
>> + }
>> +
>> + return result;
>> +}
>> +
>> +subsys_initcall(crash_hotplug_init);
>> +#endif
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 969e8f52f7da..f2f9d41ce5df 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -276,6 +276,11 @@ struct kimage *do_kimage_alloc_init(void)
>> /* Initialize the list of unusable pages */
>> INIT_LIST_HEAD(&image->unusable_pages);
>>
>> +#ifdef CONFIG_CRASH_HOTPLUG
>> + image->elfcorehdr_index = -1;
>> + image->elfcorehdr_updated = false;
>> +#endif
>> +
>> return image;
>> }
>>
>> --
>> 2.31.1
>>
>
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-14 13:28 ` Eric DeVolder
@ 2023-03-14 14:22 ` Baoquan He
-1 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-14 14:22 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/14/23 at 08:28am, Eric DeVolder wrote:
......
> > > +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
> > > +{
> > > + switch (val) {
> > > + case MEM_ONLINE:
> > > + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
> > > + KEXEC_CRASH_HP_INVALID_CPU);
> > > + break;
> > > +
> > > + case MEM_OFFLINE:
> > > + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
> > > + KEXEC_CRASH_HP_INVALID_CPU);
> > > + break;
> > > + }
> > > + return NOTIFY_OK;
> > > +}
> > > +
> > > +static struct notifier_block crash_memhp_nb = {
> > > + .notifier_call = crash_memhp_notifier,
> > > + .priority = 0
> > > +};
> > > +
> >
> > Because for_each_possible_cpu() is taken in
> > crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
> > hotplug or doesn't do anything with this patchset. This cpu part in
> > infrastructure is only for the later powerpc usage, right?
>
> That is true, yes.
Given this patchset is aimed at crash hotplug on x86, while obviously it
does't need to have the cpu hotplug support on x86 since the
for_each_possible_cpu() adjustment. People looking into this may be
confused if they don't follow the discussion thread of v18. Do we need
to mention this in cover letter or somewhere else? I could miss that
though it is has been told, please ignore this if yes.
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-14 14:22 ` Baoquan He
0 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-14 14:22 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/14/23 at 08:28am, Eric DeVolder wrote:
......
> > > +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
> > > +{
> > > + switch (val) {
> > > + case MEM_ONLINE:
> > > + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
> > > + KEXEC_CRASH_HP_INVALID_CPU);
> > > + break;
> > > +
> > > + case MEM_OFFLINE:
> > > + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
> > > + KEXEC_CRASH_HP_INVALID_CPU);
> > > + break;
> > > + }
> > > + return NOTIFY_OK;
> > > +}
> > > +
> > > +static struct notifier_block crash_memhp_nb = {
> > > + .notifier_call = crash_memhp_notifier,
> > > + .priority = 0
> > > +};
> > > +
> >
> > Because for_each_possible_cpu() is taken in
> > crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
> > hotplug or doesn't do anything with this patchset. This cpu part in
> > infrastructure is only for the later powerpc usage, right?
>
> That is true, yes.
Given this patchset is aimed at crash hotplug on x86, while obviously it
does't need to have the cpu hotplug support on x86 since the
for_each_possible_cpu() adjustment. People looking into this may be
confused if they don't follow the discussion thread of v18. Do we need
to mention this in cover letter or somewhere else? I could miss that
though it is has been told, please ignore this if yes.
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-14 14:22 ` Baoquan He
@ 2023-03-14 14:25 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-14 14:25 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/14/23 09:22, Baoquan He wrote:
> On 03/14/23 at 08:28am, Eric DeVolder wrote:
> ......
>>>> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
>>>> +{
>>>> + switch (val) {
>>>> + case MEM_ONLINE:
>>>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
>>>> + KEXEC_CRASH_HP_INVALID_CPU);
>>>> + break;
>>>> +
>>>> + case MEM_OFFLINE:
>>>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
>>>> + KEXEC_CRASH_HP_INVALID_CPU);
>>>> + break;
>>>> + }
>>>> + return NOTIFY_OK;
>>>> +}
>>>> +
>>>> +static struct notifier_block crash_memhp_nb = {
>>>> + .notifier_call = crash_memhp_notifier,
>>>> + .priority = 0
>>>> +};
>>>> +
>>>
>>> Because for_each_possible_cpu() is taken in
>>> crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
>>> hotplug or doesn't do anything with this patchset. This cpu part in
>>> infrastructure is only for the later powerpc usage, right?
>>
>> That is true, yes.
>
> Given this patchset is aimed at crash hotplug on x86, while obviously it
> does't need to have the cpu hotplug support on x86 since the
> for_each_possible_cpu() adjustment. People looking into this may be
> confused if they don't follow the discussion thread of v18. Do we need
> to mention this in cover letter or somewhere else? I could miss that
> though it is has been told, please ignore this if yes.
>
Good point, I'll update the cover letter to reflect this.
eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-14 14:25 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-14 14:25 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/14/23 09:22, Baoquan He wrote:
> On 03/14/23 at 08:28am, Eric DeVolder wrote:
> ......
>>>> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
>>>> +{
>>>> + switch (val) {
>>>> + case MEM_ONLINE:
>>>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
>>>> + KEXEC_CRASH_HP_INVALID_CPU);
>>>> + break;
>>>> +
>>>> + case MEM_OFFLINE:
>>>> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
>>>> + KEXEC_CRASH_HP_INVALID_CPU);
>>>> + break;
>>>> + }
>>>> + return NOTIFY_OK;
>>>> +}
>>>> +
>>>> +static struct notifier_block crash_memhp_nb = {
>>>> + .notifier_call = crash_memhp_notifier,
>>>> + .priority = 0
>>>> +};
>>>> +
>>>
>>> Because for_each_possible_cpu() is taken in
>>> crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
>>> hotplug or doesn't do anything with this patchset. This cpu part in
>>> infrastructure is only for the later powerpc usage, right?
>>
>> That is true, yes.
>
> Given this patchset is aimed at crash hotplug on x86, while obviously it
> does't need to have the cpu hotplug support on x86 since the
> for_each_possible_cpu() adjustment. People looking into this may be
> confused if they don't follow the discussion thread of v18. Do we need
> to mention this in cover letter or somewhere else? I could miss that
> though it is has been told, please ignore this if yes.
>
Good point, I'll update the cover letter to reflect this.
eric
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-06 16:22 ` Eric DeVolder
@ 2023-03-16 10:11 ` Baoquan He
-1 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-16 10:11 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/06/23 at 11:22am, Eric DeVolder wrote:
......
> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> +{
> + /* Obtain lock while changing crash information */
> + if (kexec_trylock()) {
> +
> + /* Check kdump is loaded */
> + if (kexec_crash_image) {
> + struct kimage *image = kexec_crash_image;
> +
> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> + else
> + pr_debug("hp_action %u\n", hp_action);
> +
> + /*
> + * When the struct kimage is allocated, the elfcorehdr_index
> + * is set to -1. Find the segment containing the elfcorehdr,
> + * if not already found. This works for both the kexec_load
> + * and kexec_file_load paths.
> + */
> + if (image->elfcorehdr_index < 0) {
> + unsigned long mem;
> + unsigned char *ptr;
> + unsigned int n;
> +
> + for (n = 0; n < image->nr_segments; n++) {
> + mem = image->segment[n].mem;
> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> + if (ptr) {
> + /* The segment containing elfcorehdr */
> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> + image->elfcorehdr_index = (int)n;
> + }
> + kunmap_local(ptr);
> + }
> + }
> + }
> +
> + if (image->elfcorehdr_index < 0) {
> + pr_err("unable to locate elfcorehdr segment");
> + goto out;
> + }
> +
> + /* Needed in order for the segments to be updated */
> + arch_kexec_unprotect_crashkres();
> +
> + /* Differentiate between normal load and hotplug update */
> + image->hp_action = hp_action;
> +
> + /* Now invoke arch-specific update handler */
> + arch_crash_handle_hotplug_event(image);
> +
> + /* No longer handling a hotplug event */
> + image->hp_action = KEXEC_CRASH_HP_NONE;
> + image->elfcorehdr_updated = true;
It's good to initialize the image->hp_action here, however where do
you check it? Do you plan to add some check somewhere?
> +
> + /* Change back to read-only */
> + arch_kexec_protect_crashkres();
> + }
> +
> +out:
> + /* Release lock now that update complete */
> + kexec_unlock();
> + }
> +}
......
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-16 10:11 ` Baoquan He
0 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-16 10:11 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/06/23 at 11:22am, Eric DeVolder wrote:
......
> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> +{
> + /* Obtain lock while changing crash information */
> + if (kexec_trylock()) {
> +
> + /* Check kdump is loaded */
> + if (kexec_crash_image) {
> + struct kimage *image = kexec_crash_image;
> +
> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> + else
> + pr_debug("hp_action %u\n", hp_action);
> +
> + /*
> + * When the struct kimage is allocated, the elfcorehdr_index
> + * is set to -1. Find the segment containing the elfcorehdr,
> + * if not already found. This works for both the kexec_load
> + * and kexec_file_load paths.
> + */
> + if (image->elfcorehdr_index < 0) {
> + unsigned long mem;
> + unsigned char *ptr;
> + unsigned int n;
> +
> + for (n = 0; n < image->nr_segments; n++) {
> + mem = image->segment[n].mem;
> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> + if (ptr) {
> + /* The segment containing elfcorehdr */
> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> + image->elfcorehdr_index = (int)n;
> + }
> + kunmap_local(ptr);
> + }
> + }
> + }
> +
> + if (image->elfcorehdr_index < 0) {
> + pr_err("unable to locate elfcorehdr segment");
> + goto out;
> + }
> +
> + /* Needed in order for the segments to be updated */
> + arch_kexec_unprotect_crashkres();
> +
> + /* Differentiate between normal load and hotplug update */
> + image->hp_action = hp_action;
> +
> + /* Now invoke arch-specific update handler */
> + arch_crash_handle_hotplug_event(image);
> +
> + /* No longer handling a hotplug event */
> + image->hp_action = KEXEC_CRASH_HP_NONE;
> + image->elfcorehdr_updated = true;
It's good to initialize the image->hp_action here, however where do
you check it? Do you plan to add some check somewhere?
> +
> + /* Change back to read-only */
> + arch_kexec_protect_crashkres();
> + }
> +
> +out:
> + /* Release lock now that update complete */
> + kexec_unlock();
> + }
> +}
......
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-16 10:11 ` Baoquan He
@ 2023-03-16 14:44 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-16 14:44 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/16/23 05:11, Baoquan He wrote:
> On 03/06/23 at 11:22am, Eric DeVolder wrote:
> ......
>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>> +{
>> + /* Obtain lock while changing crash information */
>> + if (kexec_trylock()) {
>> +
>> + /* Check kdump is loaded */
>> + if (kexec_crash_image) {
>> + struct kimage *image = kexec_crash_image;
>> +
>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>> + else
>> + pr_debug("hp_action %u\n", hp_action);
>> +
>> + /*
>> + * When the struct kimage is allocated, the elfcorehdr_index
>> + * is set to -1. Find the segment containing the elfcorehdr,
>> + * if not already found. This works for both the kexec_load
>> + * and kexec_file_load paths.
>> + */
>> + if (image->elfcorehdr_index < 0) {
>> + unsigned long mem;
>> + unsigned char *ptr;
>> + unsigned int n;
>> +
>> + for (n = 0; n < image->nr_segments; n++) {
>> + mem = image->segment[n].mem;
>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>> + if (ptr) {
>> + /* The segment containing elfcorehdr */
>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>> + image->elfcorehdr_index = (int)n;
>> + }
>> + kunmap_local(ptr);
>> + }
>> + }
>> + }
>> +
>> + if (image->elfcorehdr_index < 0) {
>> + pr_err("unable to locate elfcorehdr segment");
>> + goto out;
>> + }
>> +
>> + /* Needed in order for the segments to be updated */
>> + arch_kexec_unprotect_crashkres();
>> +
>> + /* Differentiate between normal load and hotplug update */
>> + image->hp_action = hp_action;
>> +
>> + /* Now invoke arch-specific update handler */
>> + arch_crash_handle_hotplug_event(image);
>> +
>> + /* No longer handling a hotplug event */
>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>> + image->elfcorehdr_updated = true;
>
> It's good to initialize the image->hp_action here, however where do
> you check it? Do you plan to add some check somewhere?
Hi Baoquan,
The hp_action member is initialized to 0 in do_image_alloc_init(). I've
mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
delineate that a hotplug event handling has completed. You can see
imae->hp_action set to hp_action to capture what the triggering event
was, as passed into this function.
I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
Thanks!
eric
>
>> +
>> + /* Change back to read-only */
>> + arch_kexec_protect_crashkres();
>> + }
>> +
>> +out:
>> + /* Release lock now that update complete */
>> + kexec_unlock();
>> + }
>> +}
> ......
>
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-16 14:44 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-16 14:44 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/16/23 05:11, Baoquan He wrote:
> On 03/06/23 at 11:22am, Eric DeVolder wrote:
> ......
>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>> +{
>> + /* Obtain lock while changing crash information */
>> + if (kexec_trylock()) {
>> +
>> + /* Check kdump is loaded */
>> + if (kexec_crash_image) {
>> + struct kimage *image = kexec_crash_image;
>> +
>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>> + else
>> + pr_debug("hp_action %u\n", hp_action);
>> +
>> + /*
>> + * When the struct kimage is allocated, the elfcorehdr_index
>> + * is set to -1. Find the segment containing the elfcorehdr,
>> + * if not already found. This works for both the kexec_load
>> + * and kexec_file_load paths.
>> + */
>> + if (image->elfcorehdr_index < 0) {
>> + unsigned long mem;
>> + unsigned char *ptr;
>> + unsigned int n;
>> +
>> + for (n = 0; n < image->nr_segments; n++) {
>> + mem = image->segment[n].mem;
>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>> + if (ptr) {
>> + /* The segment containing elfcorehdr */
>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>> + image->elfcorehdr_index = (int)n;
>> + }
>> + kunmap_local(ptr);
>> + }
>> + }
>> + }
>> +
>> + if (image->elfcorehdr_index < 0) {
>> + pr_err("unable to locate elfcorehdr segment");
>> + goto out;
>> + }
>> +
>> + /* Needed in order for the segments to be updated */
>> + arch_kexec_unprotect_crashkres();
>> +
>> + /* Differentiate between normal load and hotplug update */
>> + image->hp_action = hp_action;
>> +
>> + /* Now invoke arch-specific update handler */
>> + arch_crash_handle_hotplug_event(image);
>> +
>> + /* No longer handling a hotplug event */
>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>> + image->elfcorehdr_updated = true;
>
> It's good to initialize the image->hp_action here, however where do
> you check it? Do you plan to add some check somewhere?
Hi Baoquan,
The hp_action member is initialized to 0 in do_image_alloc_init(). I've
mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
delineate that a hotplug event handling has completed. You can see
imae->hp_action set to hp_action to capture what the triggering event
was, as passed into this function.
I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
Thanks!
eric
>
>> +
>> + /* Change back to read-only */
>> + arch_kexec_protect_crashkres();
>> + }
>> +
>> +out:
>> + /* Release lock now that update complete */
>> + kexec_unlock();
>> + }
>> +}
> ......
>
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-16 14:44 ` Eric DeVolder
@ 2023-03-16 15:47 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-16 15:47 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/16/23 09:44, Eric DeVolder wrote:
>
>
> On 3/16/23 05:11, Baoquan He wrote:
>> On 03/06/23 at 11:22am, Eric DeVolder wrote:
>> ......
>>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>>> +{
>>> + /* Obtain lock while changing crash information */
>>> + if (kexec_trylock()) {
>>> +
>>> + /* Check kdump is loaded */
>>> + if (kexec_crash_image) {
>>> + struct kimage *image = kexec_crash_image;
>>> +
>>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>>> + else
>>> + pr_debug("hp_action %u\n", hp_action);
>>> +
>>> + /*
>>> + * When the struct kimage is allocated, the elfcorehdr_index
>>> + * is set to -1. Find the segment containing the elfcorehdr,
>>> + * if not already found. This works for both the kexec_load
>>> + * and kexec_file_load paths.
>>> + */
>>> + if (image->elfcorehdr_index < 0) {
>>> + unsigned long mem;
>>> + unsigned char *ptr;
>>> + unsigned int n;
>>> +
>>> + for (n = 0; n < image->nr_segments; n++) {
>>> + mem = image->segment[n].mem;
>>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>>> + if (ptr) {
>>> + /* The segment containing elfcorehdr */
>>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>>> + image->elfcorehdr_index = (int)n;
>>> + }
>>> + kunmap_local(ptr);
>>> + }
>>> + }
>>> + }
>>> +
>>> + if (image->elfcorehdr_index < 0) {
>>> + pr_err("unable to locate elfcorehdr segment");
>>> + goto out;
>>> + }
>>> +
>>> + /* Needed in order for the segments to be updated */
>>> + arch_kexec_unprotect_crashkres();
>>> +
>>> + /* Differentiate between normal load and hotplug update */
>>> + image->hp_action = hp_action;
>>> +
>>> + /* Now invoke arch-specific update handler */
>>> + arch_crash_handle_hotplug_event(image);
>>> +
>>> + /* No longer handling a hotplug event */
>>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>>> + image->elfcorehdr_updated = true;
>>
>> It's good to initialize the image->hp_action here, however where do
>> you check it? Do you plan to add some check somewhere?
>
> Hi Baoquan,
> The hp_action member is initialized to 0 in do_image_alloc_init(). I've
> mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
>
> But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
> delineate that a hotplug event handling has completed. You can see
> imae->hp_action set to hp_action to capture what the triggering event
> was, as passed into this function.
>
> I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
> in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
>
> Thanks!
> eric
Baoquan, as you are currently working through v19, please let me know when I should put out v20 with
this and Sourabh's feedback.
Thanks,
eric
>
>
>>
>>> +
>>> + /* Change back to read-only */
>>> + arch_kexec_protect_crashkres();
>>> + }
>>> +
>>> +out:
>>> + /* Release lock now that update complete */
>>> + kexec_unlock();
>>> + }
>>> +}
>> ......
>>
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-16 15:47 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-16 15:47 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/16/23 09:44, Eric DeVolder wrote:
>
>
> On 3/16/23 05:11, Baoquan He wrote:
>> On 03/06/23 at 11:22am, Eric DeVolder wrote:
>> ......
>>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>>> +{
>>> + /* Obtain lock while changing crash information */
>>> + if (kexec_trylock()) {
>>> +
>>> + /* Check kdump is loaded */
>>> + if (kexec_crash_image) {
>>> + struct kimage *image = kexec_crash_image;
>>> +
>>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>>> + else
>>> + pr_debug("hp_action %u\n", hp_action);
>>> +
>>> + /*
>>> + * When the struct kimage is allocated, the elfcorehdr_index
>>> + * is set to -1. Find the segment containing the elfcorehdr,
>>> + * if not already found. This works for both the kexec_load
>>> + * and kexec_file_load paths.
>>> + */
>>> + if (image->elfcorehdr_index < 0) {
>>> + unsigned long mem;
>>> + unsigned char *ptr;
>>> + unsigned int n;
>>> +
>>> + for (n = 0; n < image->nr_segments; n++) {
>>> + mem = image->segment[n].mem;
>>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>>> + if (ptr) {
>>> + /* The segment containing elfcorehdr */
>>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>>> + image->elfcorehdr_index = (int)n;
>>> + }
>>> + kunmap_local(ptr);
>>> + }
>>> + }
>>> + }
>>> +
>>> + if (image->elfcorehdr_index < 0) {
>>> + pr_err("unable to locate elfcorehdr segment");
>>> + goto out;
>>> + }
>>> +
>>> + /* Needed in order for the segments to be updated */
>>> + arch_kexec_unprotect_crashkres();
>>> +
>>> + /* Differentiate between normal load and hotplug update */
>>> + image->hp_action = hp_action;
>>> +
>>> + /* Now invoke arch-specific update handler */
>>> + arch_crash_handle_hotplug_event(image);
>>> +
>>> + /* No longer handling a hotplug event */
>>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>>> + image->elfcorehdr_updated = true;
>>
>> It's good to initialize the image->hp_action here, however where do
>> you check it? Do you plan to add some check somewhere?
>
> Hi Baoquan,
> The hp_action member is initialized to 0 in do_image_alloc_init(). I've
> mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
>
> But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
> delineate that a hotplug event handling has completed. You can see
> imae->hp_action set to hp_action to capture what the triggering event
> was, as passed into this function.
>
> I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
> in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
>
> Thanks!
> eric
Baoquan, as you are currently working through v19, please let me know when I should put out v20 with
this and Sourabh's feedback.
Thanks,
eric
>
>
>>
>>> +
>>> + /* Change back to read-only */
>>> + arch_kexec_protect_crashkres();
>>> + }
>>> +
>>> +out:
>>> + /* Release lock now that update complete */
>>> + kexec_unlock();
>>> + }
>>> +}
>> ......
>>
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-16 14:44 ` Eric DeVolder
@ 2023-03-17 9:04 ` Baoquan He
-1 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-17 9:04 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/16/23 at 09:44am, Eric DeVolder wrote:
>
>
> On 3/16/23 05:11, Baoquan He wrote:
> > On 03/06/23 at 11:22am, Eric DeVolder wrote:
> > ......
> > > +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> > > +{
> > > + /* Obtain lock while changing crash information */
> > > + if (kexec_trylock()) {
> > > +
> > > + /* Check kdump is loaded */
> > > + if (kexec_crash_image) {
> > > + struct kimage *image = kexec_crash_image;
> > > +
> > > + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> > > + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> > > + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> > > + else
> > > + pr_debug("hp_action %u\n", hp_action);
> > > +
> > > + /*
> > > + * When the struct kimage is allocated, the elfcorehdr_index
> > > + * is set to -1. Find the segment containing the elfcorehdr,
> > > + * if not already found. This works for both the kexec_load
> > > + * and kexec_file_load paths.
> > > + */
> > > + if (image->elfcorehdr_index < 0) {
> > > + unsigned long mem;
> > > + unsigned char *ptr;
> > > + unsigned int n;
> > > +
> > > + for (n = 0; n < image->nr_segments; n++) {
> > > + mem = image->segment[n].mem;
> > > + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> > > + if (ptr) {
> > > + /* The segment containing elfcorehdr */
> > > + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> > > + image->elfcorehdr_index = (int)n;
> > > + }
> > > + kunmap_local(ptr);
> > > + }
> > > + }
> > > + }
> > > +
> > > + if (image->elfcorehdr_index < 0) {
> > > + pr_err("unable to locate elfcorehdr segment");
> > > + goto out;
> > > + }
> > > +
> > > + /* Needed in order for the segments to be updated */
> > > + arch_kexec_unprotect_crashkres();
> > > +
> > > + /* Differentiate between normal load and hotplug update */
> > > + image->hp_action = hp_action;
> > > +
> > > + /* Now invoke arch-specific update handler */
> > > + arch_crash_handle_hotplug_event(image);
> > > +
> > > + /* No longer handling a hotplug event */
> > > + image->hp_action = KEXEC_CRASH_HP_NONE;
> > > + image->elfcorehdr_updated = true;
> >
> > It's good to initialize the image->hp_action here, however where do
> > you check it? Do you plan to add some check somewhere?
>
> Hi Baoquan,
> The hp_action member is initialized to 0 in do_image_alloc_init(). I've
> mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
>
> But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
> delineate that a hotplug event handling has completed. You can see
> imae->hp_action set to hp_action to capture what the triggering event
> was, as passed into this function.
>
> I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
> in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
Yeah, setting image->hp_action = KEXEC_CRASH_HP_NONE in
do_kimage_alloc_init() will make code clearer. While I am wondering if
we don't initialie image->hp_action to KEXEC_CRASH_HP_NONE, and don't
set image->hp_action to KEXEC_CRASH_HP_NONE to actually delineate that a
hotplug event handling has completed, what will happen?
I mean you set image->hp_action to KEXEC_CRASH_HP_NONE explicitly, where
do you check if it should not be KEXEC_CRASH_HP_NONE? In
crash_handle_hotplug_event(), we took __kexec_lock and assign the passed
hp_action anyway.
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-17 9:04 ` Baoquan He
0 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-17 9:04 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/16/23 at 09:44am, Eric DeVolder wrote:
>
>
> On 3/16/23 05:11, Baoquan He wrote:
> > On 03/06/23 at 11:22am, Eric DeVolder wrote:
> > ......
> > > +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> > > +{
> > > + /* Obtain lock while changing crash information */
> > > + if (kexec_trylock()) {
> > > +
> > > + /* Check kdump is loaded */
> > > + if (kexec_crash_image) {
> > > + struct kimage *image = kexec_crash_image;
> > > +
> > > + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> > > + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> > > + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> > > + else
> > > + pr_debug("hp_action %u\n", hp_action);
> > > +
> > > + /*
> > > + * When the struct kimage is allocated, the elfcorehdr_index
> > > + * is set to -1. Find the segment containing the elfcorehdr,
> > > + * if not already found. This works for both the kexec_load
> > > + * and kexec_file_load paths.
> > > + */
> > > + if (image->elfcorehdr_index < 0) {
> > > + unsigned long mem;
> > > + unsigned char *ptr;
> > > + unsigned int n;
> > > +
> > > + for (n = 0; n < image->nr_segments; n++) {
> > > + mem = image->segment[n].mem;
> > > + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> > > + if (ptr) {
> > > + /* The segment containing elfcorehdr */
> > > + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> > > + image->elfcorehdr_index = (int)n;
> > > + }
> > > + kunmap_local(ptr);
> > > + }
> > > + }
> > > + }
> > > +
> > > + if (image->elfcorehdr_index < 0) {
> > > + pr_err("unable to locate elfcorehdr segment");
> > > + goto out;
> > > + }
> > > +
> > > + /* Needed in order for the segments to be updated */
> > > + arch_kexec_unprotect_crashkres();
> > > +
> > > + /* Differentiate between normal load and hotplug update */
> > > + image->hp_action = hp_action;
> > > +
> > > + /* Now invoke arch-specific update handler */
> > > + arch_crash_handle_hotplug_event(image);
> > > +
> > > + /* No longer handling a hotplug event */
> > > + image->hp_action = KEXEC_CRASH_HP_NONE;
> > > + image->elfcorehdr_updated = true;
> >
> > It's good to initialize the image->hp_action here, however where do
> > you check it? Do you plan to add some check somewhere?
>
> Hi Baoquan,
> The hp_action member is initialized to 0 in do_image_alloc_init(). I've
> mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
>
> But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
> delineate that a hotplug event handling has completed. You can see
> imae->hp_action set to hp_action to capture what the triggering event
> was, as passed into this function.
>
> I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
> in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
Yeah, setting image->hp_action = KEXEC_CRASH_HP_NONE in
do_kimage_alloc_init() will make code clearer. While I am wondering if
we don't initialie image->hp_action to KEXEC_CRASH_HP_NONE, and don't
set image->hp_action to KEXEC_CRASH_HP_NONE to actually delineate that a
hotplug event handling has completed, what will happen?
I mean you set image->hp_action to KEXEC_CRASH_HP_NONE explicitly, where
do you check if it should not be KEXEC_CRASH_HP_NONE? In
crash_handle_hotplug_event(), we took __kexec_lock and assign the passed
hp_action anyway.
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-16 15:47 ` Eric DeVolder
@ 2023-03-17 9:30 ` Baoquan He
-1 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-17 9:30 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/16/23 at 10:47am, Eric DeVolder wrote:
>
>
> On 3/16/23 09:44, Eric DeVolder wrote:
> >
> >
> > On 3/16/23 05:11, Baoquan He wrote:
> > > On 03/06/23 at 11:22am, Eric DeVolder wrote:
> > > ......
> > > > +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> > > > +{
> > > > + /* Obtain lock while changing crash information */
> > > > + if (kexec_trylock()) {
> > > > +
> > > > + /* Check kdump is loaded */
> > > > + if (kexec_crash_image) {
> > > > + struct kimage *image = kexec_crash_image;
> > > > +
> > > > + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> > > > + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> > > > + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> > > > + else
> > > > + pr_debug("hp_action %u\n", hp_action);
> > > > +
> > > > + /*
> > > > + * When the struct kimage is allocated, the elfcorehdr_index
> > > > + * is set to -1. Find the segment containing the elfcorehdr,
> > > > + * if not already found. This works for both the kexec_load
> > > > + * and kexec_file_load paths.
> > > > + */
> > > > + if (image->elfcorehdr_index < 0) {
> > > > + unsigned long mem;
> > > > + unsigned char *ptr;
> > > > + unsigned int n;
> > > > +
> > > > + for (n = 0; n < image->nr_segments; n++) {
> > > > + mem = image->segment[n].mem;
> > > > + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> > > > + if (ptr) {
> > > > + /* The segment containing elfcorehdr */
> > > > + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> > > > + image->elfcorehdr_index = (int)n;
> > > > + }
> > > > + kunmap_local(ptr);
> > > > + }
> > > > + }
> > > > + }
> > > > +
> > > > + if (image->elfcorehdr_index < 0) {
> > > > + pr_err("unable to locate elfcorehdr segment");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + /* Needed in order for the segments to be updated */
> > > > + arch_kexec_unprotect_crashkres();
> > > > +
> > > > + /* Differentiate between normal load and hotplug update */
> > > > + image->hp_action = hp_action;
> > > > +
> > > > + /* Now invoke arch-specific update handler */
> > > > + arch_crash_handle_hotplug_event(image);
> > > > +
> > > > + /* No longer handling a hotplug event */
> > > > + image->hp_action = KEXEC_CRASH_HP_NONE;
> > > > + image->elfcorehdr_updated = true;
> > >
> > > It's good to initialize the image->hp_action here, however where do
> > > you check it? Do you plan to add some check somewhere?
> >
> > Hi Baoquan,
> > The hp_action member is initialized to 0 in do_image_alloc_init(). I've
> > mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
> >
> > But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
> > delineate that a hotplug event handling has completed. You can see
> > imae->hp_action set to hp_action to capture what the triggering event
> > was, as passed into this function.
> >
> > I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
> > in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
> >
> > Thanks!
> > eric
>
> Baoquan, as you are currently working through v19, please let me know when I
> should put out v20 with this and Sourabh's feedback.
> Thanks,
> eric
The overall serial looks good to me other than the nitpicks.
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-17 9:30 ` Baoquan He
0 siblings, 0 replies; 46+ messages in thread
From: Baoquan He @ 2023-03-17 9:30 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 03/16/23 at 10:47am, Eric DeVolder wrote:
>
>
> On 3/16/23 09:44, Eric DeVolder wrote:
> >
> >
> > On 3/16/23 05:11, Baoquan He wrote:
> > > On 03/06/23 at 11:22am, Eric DeVolder wrote:
> > > ......
> > > > +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> > > > +{
> > > > + /* Obtain lock while changing crash information */
> > > > + if (kexec_trylock()) {
> > > > +
> > > > + /* Check kdump is loaded */
> > > > + if (kexec_crash_image) {
> > > > + struct kimage *image = kexec_crash_image;
> > > > +
> > > > + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> > > > + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> > > > + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
> > > > + else
> > > > + pr_debug("hp_action %u\n", hp_action);
> > > > +
> > > > + /*
> > > > + * When the struct kimage is allocated, the elfcorehdr_index
> > > > + * is set to -1. Find the segment containing the elfcorehdr,
> > > > + * if not already found. This works for both the kexec_load
> > > > + * and kexec_file_load paths.
> > > > + */
> > > > + if (image->elfcorehdr_index < 0) {
> > > > + unsigned long mem;
> > > > + unsigned char *ptr;
> > > > + unsigned int n;
> > > > +
> > > > + for (n = 0; n < image->nr_segments; n++) {
> > > > + mem = image->segment[n].mem;
> > > > + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
> > > > + if (ptr) {
> > > > + /* The segment containing elfcorehdr */
> > > > + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
> > > > + image->elfcorehdr_index = (int)n;
> > > > + }
> > > > + kunmap_local(ptr);
> > > > + }
> > > > + }
> > > > + }
> > > > +
> > > > + if (image->elfcorehdr_index < 0) {
> > > > + pr_err("unable to locate elfcorehdr segment");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + /* Needed in order for the segments to be updated */
> > > > + arch_kexec_unprotect_crashkres();
> > > > +
> > > > + /* Differentiate between normal load and hotplug update */
> > > > + image->hp_action = hp_action;
> > > > +
> > > > + /* Now invoke arch-specific update handler */
> > > > + arch_crash_handle_hotplug_event(image);
> > > > +
> > > > + /* No longer handling a hotplug event */
> > > > + image->hp_action = KEXEC_CRASH_HP_NONE;
> > > > + image->elfcorehdr_updated = true;
> > >
> > > It's good to initialize the image->hp_action here, however where do
> > > you check it? Do you plan to add some check somewhere?
> >
> > Hi Baoquan,
> > The hp_action member is initialized to 0 in do_image_alloc_init(). I've
> > mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
> >
> > But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
> > delineate that a hotplug event handling has completed. You can see
> > imae->hp_action set to hp_action to capture what the triggering event
> > was, as passed into this function.
> >
> > I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
> > in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
> >
> > Thanks!
> > eric
>
> Baoquan, as you are currently working through v19, please let me know when I
> should put out v20 with this and Sourabh's feedback.
> Thanks,
> eric
The overall serial looks good to me other than the nitpicks.
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
2023-03-17 9:04 ` Baoquan He
@ 2023-03-17 18:13 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-17 18:13 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/17/23 04:04, Baoquan He wrote:
> On 03/16/23 at 09:44am, Eric DeVolder wrote:
>>
>>
>> On 3/16/23 05:11, Baoquan He wrote:
>>> On 03/06/23 at 11:22am, Eric DeVolder wrote:
>>> ......
>>>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>>>> +{
>>>> + /* Obtain lock while changing crash information */
>>>> + if (kexec_trylock()) {
>>>> +
>>>> + /* Check kdump is loaded */
>>>> + if (kexec_crash_image) {
>>>> + struct kimage *image = kexec_crash_image;
>>>> +
>>>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>>>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>>>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>>>> + else
>>>> + pr_debug("hp_action %u\n", hp_action);
>>>> +
>>>> + /*
>>>> + * When the struct kimage is allocated, the elfcorehdr_index
>>>> + * is set to -1. Find the segment containing the elfcorehdr,
>>>> + * if not already found. This works for both the kexec_load
>>>> + * and kexec_file_load paths.
>>>> + */
>>>> + if (image->elfcorehdr_index < 0) {
>>>> + unsigned long mem;
>>>> + unsigned char *ptr;
>>>> + unsigned int n;
>>>> +
>>>> + for (n = 0; n < image->nr_segments; n++) {
>>>> + mem = image->segment[n].mem;
>>>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>>>> + if (ptr) {
>>>> + /* The segment containing elfcorehdr */
>>>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>>>> + image->elfcorehdr_index = (int)n;
>>>> + }
>>>> + kunmap_local(ptr);
>>>> + }
>>>> + }
>>>> + }
>>>> +
>>>> + if (image->elfcorehdr_index < 0) {
>>>> + pr_err("unable to locate elfcorehdr segment");
>>>> + goto out;
>>>> + }
>>>> +
>>>> + /* Needed in order for the segments to be updated */
>>>> + arch_kexec_unprotect_crashkres();
>>>> +
>>>> + /* Differentiate between normal load and hotplug update */
>>>> + image->hp_action = hp_action;
>>>> +
>>>> + /* Now invoke arch-specific update handler */
>>>> + arch_crash_handle_hotplug_event(image);
>>>> +
>>>> + /* No longer handling a hotplug event */
>>>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>>>> + image->elfcorehdr_updated = true;
>>>
>>> It's good to initialize the image->hp_action here, however where do
>>> you check it? Do you plan to add some check somewhere?
>>
>> Hi Baoquan,
>> The hp_action member is initialized to 0 in do_image_alloc_init(). I've
>> mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
>>
>> But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
>> delineate that a hotplug event handling has completed. You can see
>> imae->hp_action set to hp_action to capture what the triggering event
>> was, as passed into this function.
>>
>> I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
>> in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
>
> Yeah, setting image->hp_action = KEXEC_CRASH_HP_NONE in
> do_kimage_alloc_init() will make code clearer. While I am wondering if
> we don't initialie image->hp_action to KEXEC_CRASH_HP_NONE, and don't
> set image->hp_action to KEXEC_CRASH_HP_NONE to actually delineate that a
> hotplug event handling has completed, what will happen?
Baoquan,
The KEXEC_CRASH_HP_NONE is the value 0, intentionally so that upon a alloc
of the kimage, the struct kimage is automatically zeroed and it was initialized
properly that way. I am explicitly setting hp_action to KEXEC_CRASH_HP_NONE now.
>
> I mean you set image->hp_action to KEXEC_CRASH_HP_NONE explicitly, where
> do you check if it should not be KEXEC_CRASH_HP_NONE? In
> crash_handle_hotplug_event(), we took __kexec_lock and assign the passed
> hp_action anyway.
>
The cpuhp callbacks and memory notifiers invoke crash_handle_hotplug_event()
with an appropriate hp_action. That hp_action is then stored in image->hp_action
within crash_handle_hotplug_event() for use by the arch-specific handler.
For x86, for example, the image->hp_action is used to short-circuit the arch-
specific handler if the event is a CPU plug/unplug (see patch x86/crash:
optimize cpu changes). For PPC, for example, the image->hp_action is used to
determine the appropriate actions for its FDT updates.
To summarize, the image->hp_action will be initalized to KEXEC_CRASH_HP_NONE
during do_kimage_alloc_init(). Then upon a cpu or memory plug/unplug/online/offline
event, the appropriate hp_action is stored in image->hp_action and then the
arch-specific handler called. Upon returning from the arch-specific handler,
the image->hp_action is reset back to KEXEC_CRASH_HP_NONE.
Hope this helps. I'll be posting v20 soon.
Thanks!
eric
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support
@ 2023-03-17 18:13 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-17 18:13 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, vgoyal, tglx, mingo,
bp, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 3/17/23 04:04, Baoquan He wrote:
> On 03/16/23 at 09:44am, Eric DeVolder wrote:
>>
>>
>> On 3/16/23 05:11, Baoquan He wrote:
>>> On 03/06/23 at 11:22am, Eric DeVolder wrote:
>>> ......
>>>> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>>>> +{
>>>> + /* Obtain lock while changing crash information */
>>>> + if (kexec_trylock()) {
>>>> +
>>>> + /* Check kdump is loaded */
>>>> + if (kexec_crash_image) {
>>>> + struct kimage *image = kexec_crash_image;
>>>> +
>>>> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>>>> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>>>> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
>>>> + else
>>>> + pr_debug("hp_action %u\n", hp_action);
>>>> +
>>>> + /*
>>>> + * When the struct kimage is allocated, the elfcorehdr_index
>>>> + * is set to -1. Find the segment containing the elfcorehdr,
>>>> + * if not already found. This works for both the kexec_load
>>>> + * and kexec_file_load paths.
>>>> + */
>>>> + if (image->elfcorehdr_index < 0) {
>>>> + unsigned long mem;
>>>> + unsigned char *ptr;
>>>> + unsigned int n;
>>>> +
>>>> + for (n = 0; n < image->nr_segments; n++) {
>>>> + mem = image->segment[n].mem;
>>>> + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
>>>> + if (ptr) {
>>>> + /* The segment containing elfcorehdr */
>>>> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>>>> + image->elfcorehdr_index = (int)n;
>>>> + }
>>>> + kunmap_local(ptr);
>>>> + }
>>>> + }
>>>> + }
>>>> +
>>>> + if (image->elfcorehdr_index < 0) {
>>>> + pr_err("unable to locate elfcorehdr segment");
>>>> + goto out;
>>>> + }
>>>> +
>>>> + /* Needed in order for the segments to be updated */
>>>> + arch_kexec_unprotect_crashkres();
>>>> +
>>>> + /* Differentiate between normal load and hotplug update */
>>>> + image->hp_action = hp_action;
>>>> +
>>>> + /* Now invoke arch-specific update handler */
>>>> + arch_crash_handle_hotplug_event(image);
>>>> +
>>>> + /* No longer handling a hotplug event */
>>>> + image->hp_action = KEXEC_CRASH_HP_NONE;
>>>> + image->elfcorehdr_updated = true;
>>>
>>> It's good to initialize the image->hp_action here, however where do
>>> you check it? Do you plan to add some check somewhere?
>>
>> Hi Baoquan,
>> The hp_action member is initialized to 0 in do_image_alloc_init(). I've
>> mapped KEXEC_CRASH_HP_NONE onto 0 on purpose.
>>
>> But the use of image->hp_action = KEXEC_CRASH_HP_NONE is to actually
>> delineate that a hotplug event handling has completed. You can see
>> imae->hp_action set to hp_action to capture what the triggering event
>> was, as passed into this function.
>>
>> I will go ahead and set image->hp_action = KEXEC_CRASH_HP_NONE; explicitly
>> in do_kimage_alloc_init(), as that is done for the other crash hotplug members.
>
> Yeah, setting image->hp_action = KEXEC_CRASH_HP_NONE in
> do_kimage_alloc_init() will make code clearer. While I am wondering if
> we don't initialie image->hp_action to KEXEC_CRASH_HP_NONE, and don't
> set image->hp_action to KEXEC_CRASH_HP_NONE to actually delineate that a
> hotplug event handling has completed, what will happen?
Baoquan,
The KEXEC_CRASH_HP_NONE is the value 0, intentionally so that upon a alloc
of the kimage, the struct kimage is automatically zeroed and it was initialized
properly that way. I am explicitly setting hp_action to KEXEC_CRASH_HP_NONE now.
>
> I mean you set image->hp_action to KEXEC_CRASH_HP_NONE explicitly, where
> do you check if it should not be KEXEC_CRASH_HP_NONE? In
> crash_handle_hotplug_event(), we took __kexec_lock and assign the passed
> hp_action anyway.
>
The cpuhp callbacks and memory notifiers invoke crash_handle_hotplug_event()
with an appropriate hp_action. That hp_action is then stored in image->hp_action
within crash_handle_hotplug_event() for use by the arch-specific handler.
For x86, for example, the image->hp_action is used to short-circuit the arch-
specific handler if the event is a CPU plug/unplug (see patch x86/crash:
optimize cpu changes). For PPC, for example, the image->hp_action is used to
determine the appropriate actions for its FDT updates.
To summarize, the image->hp_action will be initalized to KEXEC_CRASH_HP_NONE
during do_kimage_alloc_init(). Then upon a cpu or memory plug/unplug/online/offline
event, the appropriate hp_action is stored in image->hp_action and then the
arch-specific handler called. Upon returning from the arch-specific handler,
the image->hp_action is reset back to KEXEC_CRASH_HP_NONE.
Hope this helps. I'll be posting v20 soon.
Thanks!
eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 7/7] x86/crash: optimize cpu changes
2023-03-07 9:00 ` Sourabh Jain
@ 2023-03-17 18:42 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-17 18:42 UTC (permalink / raw)
To: Sourabh Jain, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 3/7/23 03:00, Sourabh Jain wrote:
>
> On 06/03/23 21:52, Eric DeVolder wrote:
>> This patch is dependent upon the patch 'crash: change
>> crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
>> patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
>> for all possible cpus, thus further cpu changes to the elfcorehdr
>> are not needed.
>>
>> This change works for kexec_file_load() and kexec_load() syscalls.
>> For kexec_file_load(), crash_prepare_elf64_headers() is utilized
>> directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
>> This is the kimage->file_mode term.
>> For kexec_load() syscall, one cpu or memory change will cause the
>> elfcorehdr to be updated via crash_prepare_elf64_headers() and at
>> that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
>> kimage->elfcorehdr_updated term.
>>
>> This code is intentionally *NOT* hoisted into
>> crash_handle_hotplug_event() as it would prevent the arch-specific
>> handler from running for cpu changes. This would break PPC, for
>> example, which needs to update other information besides the
>> elfcorehdr, on cpu changes.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
>> ---
>> arch/x86/kernel/crash.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index c9aaec9de775..82ea2b1bdc61 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
>> unsigned long mem, memsz;
>> unsigned long elfsz = 0;
>> + /* As crash_prepare_elf64_headers() has already described all
>> + * possible cpus, there is no need to update the elfcorehdr
>> + * for additional cpu changes. This works for both kexec_load()
>> + * and kexec_file_load() syscalls.
>> + */
>> + if ((image->file_mode || image->elfcorehdr_updated) &&
>> + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
>> + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
>> + return;
>
> I like the idea of having elfcorehdr_updated to track elfcoredhr segment updates.
> It handles the possible CPU thing for kexec_load syscall nicely.
>
> Thanks for incorporating the possible CPU change.
>
> The patch series looks good to me.
> Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>
> - Sourabh Jain
>
Thanks for the RB! Look for v20 very soon.
eric
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 7/7] x86/crash: optimize cpu changes
@ 2023-03-17 18:42 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-17 18:42 UTC (permalink / raw)
To: Sourabh Jain, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 3/7/23 03:00, Sourabh Jain wrote:
>
> On 06/03/23 21:52, Eric DeVolder wrote:
>> This patch is dependent upon the patch 'crash: change
>> crash_prepare_elf64_headers() to for_each_possible_cpu()'. With that
>> patch, crash_prepare_elf64_headers() writes out an ELF cpu PT_NOTE
>> for all possible cpus, thus further cpu changes to the elfcorehdr
>> are not needed.
>>
>> This change works for kexec_file_load() and kexec_load() syscalls.
>> For kexec_file_load(), crash_prepare_elf64_headers() is utilized
>> directly and thus all ELF cpu PT_NOTEs are in the elfcorehdr already.
>> This is the kimage->file_mode term.
>> For kexec_load() syscall, one cpu or memory change will cause the
>> elfcorehdr to be updated via crash_prepare_elf64_headers() and at
>> that point all ELF cpu PT_NOTEs are in the elfcorehdr. This is the
>> kimage->elfcorehdr_updated term.
>>
>> This code is intentionally *NOT* hoisted into
>> crash_handle_hotplug_event() as it would prevent the arch-specific
>> handler from running for cpu changes. This would break PPC, for
>> example, which needs to update other information besides the
>> elfcorehdr, on cpu changes.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
>> ---
>> arch/x86/kernel/crash.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index c9aaec9de775..82ea2b1bdc61 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -471,6 +471,16 @@ void arch_crash_handle_hotplug_event(struct kimage *image)
>> unsigned long mem, memsz;
>> unsigned long elfsz = 0;
>> + /* As crash_prepare_elf64_headers() has already described all
>> + * possible cpus, there is no need to update the elfcorehdr
>> + * for additional cpu changes. This works for both kexec_load()
>> + * and kexec_file_load() syscalls.
>> + */
>> + if ((image->file_mode || image->elfcorehdr_updated) &&
>> + ((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
>> + (image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
>> + return;
>
> I like the idea of having elfcorehdr_updated to track elfcoredhr segment updates.
> It handles the possible CPU thing for kexec_load syscall nicely.
>
> Thanks for incorporating the possible CPU change.
>
> The patch series looks good to me.
> Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>
> - Sourabh Jain
>
Thanks for the RB! Look for v20 very soon.
eric
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^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
2023-03-07 8:48 ` Sourabh Jain
@ 2023-03-17 19:12 ` Eric DeVolder
-1 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-17 19:12 UTC (permalink / raw)
To: Sourabh Jain, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 3/7/23 02:48, Sourabh Jain wrote:
> Hello Eric,
>
> On 06/03/23 21:52, Eric DeVolder wrote:
>> The function crash_prepare_elf64_headers() generates the elfcorehdr
>> which describes the cpus and memory in the system for the crash kernel.
>> In particular, it writes out ELF PT_NOTEs for memory regions and the
>> cpus in the system.
>>
>> With respect to the cpus, the current implementation utilizes
>> for_each_present_cpu() which means that as cpus are added and removed,
>> the elfcorehdr must again be updated to reflect the new set of cpus.
>>
>> The reasoning behind the change to use for_each_possible_cpu(), is:
>>
>> - At kernel boot time, all percpu crash_notes are allocated for all
>> possible cpus; that is, crash_notes are not allocated dynamically
>> when cpus are plugged/unplugged. Thus the crash_notes for each
>> possible cpu are always available.
>>
>> - The crash_prepare_elf64_headers() creates an ELF PT_NOTE per cpu.
>> Changing to for_each_possible_cpu() is valid as the crash_notes
>> pointed to by each cpu PT_NOTE are present and always valid.
>>
>> Furthermore, examining a common crash processing path of:
>>
>> kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer
>> elfcorehdr /proc/vmcore vmcore
>>
>> reveals how the ELF cpu PT_NOTEs are utilized:
>>
>> - Upon panic, each cpu is sent an IPI and shuts itself down, recording
>> its state in its crash_notes. When all cpus are shutdown, the
>> crash kernel is launched with a pointer to the elfcorehdr.
>>
>> - The crash kernel via linux/fs/proc/vmcore.c does not examine or
>> use the contents of the PT_NOTEs, it exposes them via /proc/vmcore.
>>
>> - The makedumpfile utility uses /proc/vmcore and reads the cpu
>> PT_NOTEs to craft a nr_cpus variable, which is reported in a
>> header but otherwise generally unused. Makedumpfile creates the
>> vmcore.
>>
>> - The 'crash' dump analyzer does not appear to reference the cpu
>> PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask
>> symbols and directly examines those structure contents from vmcore
>> memory. From that information it is able to determine which cpus
>> are present and online, and locate the corresponding crash_notes.
>> Said differently, it appears that 'crash' analyzer does not rely
>> on the ELF PT_NOTEs for cpus; rather it obtains the information
>> directly via kernel symbols and the memory within the vmcore.
>>
>> (There maybe other vmcore generating and analysis tools that do use
>> these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most
>> common solution.)
>>
>> This change results in the benefit of having all cpus described in
>> the elfcorehdr, and therefore reducing the need to re-generate the
>> elfcorehdr on cpu changes, at the small expense of an additional
>> 56 bytes per PT_NOTE for not-present-but-possible cpus.
>>
>> On systems where kexec_file_load() syscall is utilized, all the above
>> is valid. On systems where kexec_load() syscall is utilized, there
>> may be the need for the elfcorehdr to be regenerated once. The reason
>> being that some archs only populate the 'present' cpus in the
>> /sys/devices/system/cpus entries, which the userspace 'kexec' utility
>> uses to generate the userspace-supplied elfcorehdr. In this situation,
>> one memory or cpu change will rewrite the elfcorehdr via the
>> crash_prepare_elf64_headers() function and now all possible cpus will
>> be described, just as with kexec_file_load() syscall.
>>
>> Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
>> ---
>> kernel/crash_core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index dba4b75f7541..537b199a8774 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -365,7 +365,7 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>> ehdr->e_phentsize = sizeof(Elf64_Phdr);
>> /* Prepare one phdr of type PT_NOTE for each present CPU */
> We need to change this comment as well.
Done, thanks!
eric
>> - for_each_present_cpu(cpu) {
>> + for_each_possible_cpu(cpu) {
> - Sourabh Jain
^ permalink raw reply [flat|nested] 46+ messages in thread
* Re: [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
@ 2023-03-17 19:12 ` Eric DeVolder
0 siblings, 0 replies; 46+ messages in thread
From: Eric DeVolder @ 2023-03-17 19:12 UTC (permalink / raw)
To: Sourabh Jain, linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal
Cc: tglx, mingo, bp, dave.hansen, hpa, nramas, thomas.lendacky, robh,
efault, rppt, david, konrad.wilk, boris.ostrovsky
On 3/7/23 02:48, Sourabh Jain wrote:
> Hello Eric,
>
> On 06/03/23 21:52, Eric DeVolder wrote:
>> The function crash_prepare_elf64_headers() generates the elfcorehdr
>> which describes the cpus and memory in the system for the crash kernel.
>> In particular, it writes out ELF PT_NOTEs for memory regions and the
>> cpus in the system.
>>
>> With respect to the cpus, the current implementation utilizes
>> for_each_present_cpu() which means that as cpus are added and removed,
>> the elfcorehdr must again be updated to reflect the new set of cpus.
>>
>> The reasoning behind the change to use for_each_possible_cpu(), is:
>>
>> - At kernel boot time, all percpu crash_notes are allocated for all
>> possible cpus; that is, crash_notes are not allocated dynamically
>> when cpus are plugged/unplugged. Thus the crash_notes for each
>> possible cpu are always available.
>>
>> - The crash_prepare_elf64_headers() creates an ELF PT_NOTE per cpu.
>> Changing to for_each_possible_cpu() is valid as the crash_notes
>> pointed to by each cpu PT_NOTE are present and always valid.
>>
>> Furthermore, examining a common crash processing path of:
>>
>> kernel panic -> crash kernel -> makedumpfile -> 'crash' analyzer
>> elfcorehdr /proc/vmcore vmcore
>>
>> reveals how the ELF cpu PT_NOTEs are utilized:
>>
>> - Upon panic, each cpu is sent an IPI and shuts itself down, recording
>> its state in its crash_notes. When all cpus are shutdown, the
>> crash kernel is launched with a pointer to the elfcorehdr.
>>
>> - The crash kernel via linux/fs/proc/vmcore.c does not examine or
>> use the contents of the PT_NOTEs, it exposes them via /proc/vmcore.
>>
>> - The makedumpfile utility uses /proc/vmcore and reads the cpu
>> PT_NOTEs to craft a nr_cpus variable, which is reported in a
>> header but otherwise generally unused. Makedumpfile creates the
>> vmcore.
>>
>> - The 'crash' dump analyzer does not appear to reference the cpu
>> PT_NOTEs. Instead it looks-up the cpu_[possible|present|onlin]_mask
>> symbols and directly examines those structure contents from vmcore
>> memory. From that information it is able to determine which cpus
>> are present and online, and locate the corresponding crash_notes.
>> Said differently, it appears that 'crash' analyzer does not rely
>> on the ELF PT_NOTEs for cpus; rather it obtains the information
>> directly via kernel symbols and the memory within the vmcore.
>>
>> (There maybe other vmcore generating and analysis tools that do use
>> these PT_NOTEs, but 'makedumpfile' and 'crash' seems to be the most
>> common solution.)
>>
>> This change results in the benefit of having all cpus described in
>> the elfcorehdr, and therefore reducing the need to re-generate the
>> elfcorehdr on cpu changes, at the small expense of an additional
>> 56 bytes per PT_NOTE for not-present-but-possible cpus.
>>
>> On systems where kexec_file_load() syscall is utilized, all the above
>> is valid. On systems where kexec_load() syscall is utilized, there
>> may be the need for the elfcorehdr to be regenerated once. The reason
>> being that some archs only populate the 'present' cpus in the
>> /sys/devices/system/cpus entries, which the userspace 'kexec' utility
>> uses to generate the userspace-supplied elfcorehdr. In this situation,
>> one memory or cpu change will rewrite the elfcorehdr via the
>> crash_prepare_elf64_headers() function and now all possible cpus will
>> be described, just as with kexec_file_load() syscall.
>>
>> Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
>> ---
>> kernel/crash_core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index dba4b75f7541..537b199a8774 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -365,7 +365,7 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
>> ehdr->e_phentsize = sizeof(Elf64_Phdr);
>> /* Prepare one phdr of type PT_NOTE for each present CPU */
> We need to change this comment as well.
Done, thanks!
eric
>> - for_each_present_cpu(cpu) {
>> + for_each_possible_cpu(cpu) {
> - Sourabh Jain
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^ permalink raw reply [flat|nested] 46+ messages in thread
end of thread, other threads:[~2023-03-17 19:12 UTC | newest]
Thread overview: 46+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-03-06 16:22 [PATCH v19 0/7] crash: Kernel handling of CPU and memory hot un/plug Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-06 16:22 ` [PATCH v19 1/7] crash: move a few code bits to setup support of crash hotplug Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-06 16:22 ` [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-14 10:43 ` Baoquan He
2023-03-14 10:43 ` Baoquan He
2023-03-14 13:28 ` Eric DeVolder
2023-03-14 13:28 ` Eric DeVolder
2023-03-14 14:22 ` Baoquan He
2023-03-14 14:22 ` Baoquan He
2023-03-14 14:25 ` Eric DeVolder
2023-03-14 14:25 ` Eric DeVolder
2023-03-16 10:11 ` Baoquan He
2023-03-16 10:11 ` Baoquan He
2023-03-16 14:44 ` Eric DeVolder
2023-03-16 14:44 ` Eric DeVolder
2023-03-16 15:47 ` Eric DeVolder
2023-03-16 15:47 ` Eric DeVolder
2023-03-17 9:30 ` Baoquan He
2023-03-17 9:30 ` Baoquan He
2023-03-17 9:04 ` Baoquan He
2023-03-17 9:04 ` Baoquan He
2023-03-17 18:13 ` Eric DeVolder
2023-03-17 18:13 ` Eric DeVolder
2023-03-06 16:22 ` [PATCH v19 3/7] kexec: exclude elfcorehdr from the segment digest Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-06 16:22 ` [PATCH v19 4/7] crash: memory and cpu hotplug sysfs attributes Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-06 16:22 ` [PATCH v19 5/7] x86/crash: add x86 crash hotplug support Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-08 3:08 ` Sourabh Jain
2023-03-08 3:08 ` Sourabh Jain
2023-03-06 16:22 ` [PATCH v19 6/7] crash: change crash_prepare_elf64_headers() to for_each_possible_cpu() Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-07 8:48 ` Sourabh Jain
2023-03-07 8:48 ` Sourabh Jain
2023-03-17 19:12 ` Eric DeVolder
2023-03-17 19:12 ` Eric DeVolder
2023-03-06 16:22 ` [PATCH v19 7/7] x86/crash: optimize cpu changes Eric DeVolder
2023-03-06 16:22 ` Eric DeVolder
2023-03-07 9:00 ` Sourabh Jain
2023-03-07 9:00 ` Sourabh Jain
2023-03-17 18:42 ` Eric DeVolder
2023-03-17 18:42 ` Eric DeVolder
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