* [PATCH v13 0/7] crash: Kernel handling of CPU and memory hot un/plug
@ 2022-10-31 19:35 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:35 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 the kdump service is loaded, if a CPU or memory is hot
un/plugged, the crash elfcorehdr, which describes the CPUs
and memory in the system, must also be updated, else the resulting
vmcore is inaccurate (eg. missing either 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 previous posts I have
outlined the significant performance problems related to offloading
this activity to userspace.
This patchset introduces a generic crash hot un/plug handler that
registers with the CPU and memory notifiers. Upon CPU or memory
changes, 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
updates.
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"
These lines will cause cpu and memory hot un/plug events to be
skipped within this rule file, with this changset applied.
- 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
---
v13: 31oct2022
- 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 crash_prepare_elf64_headers()
crash: prototype change for crash_prepare_elf64_headers()
crash: add generic infrastructure for crash hotplug support
kexec: exclude elfcorehdr from the segment digest
kexec: exclude hot remove cpu from elfcorehdr notes
crash: memory and cpu hotplug sysfs attributes
x86/crash: add x86 crash hotplug support
.../admin-guide/mm/memory-hotplug.rst | 8 +
Documentation/core-api/cpu_hotplug.rst | 18 ++
arch/arm64/kernel/machine_kexec_file.c | 6 +-
arch/powerpc/kexec/file_load_64.c | 2 +-
arch/riscv/kernel/elf_kexec.c | 7 +-
arch/x86/include/asm/kexec.h | 14 +
arch/x86/kernel/crash.c | 110 +++++++-
drivers/base/cpu.c | 14 +
drivers/base/memory.c | 13 +
include/linux/crash_core.h | 8 +
include/linux/kexec.h | 54 +++-
kernel/crash_core.c | 255 ++++++++++++++++++
kernel/kexec_file.c | 105 +-------
13 files changed, 502 insertions(+), 112 deletions(-)
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* [PATCH v13 0/7] crash: Kernel handling of CPU and memory hot un/plug
@ 2022-10-31 19:35 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:35 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 the kdump service is loaded, if a CPU or memory is hot
un/plugged, the crash elfcorehdr, which describes the CPUs
and memory in the system, must also be updated, else the resulting
vmcore is inaccurate (eg. missing either 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 previous posts I have
outlined the significant performance problems related to offloading
this activity to userspace.
This patchset introduces a generic crash hot un/plug handler that
registers with the CPU and memory notifiers. Upon CPU or memory
changes, 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
updates.
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"
These lines will cause cpu and memory hot un/plug events to be
skipped within this rule file, with this changset applied.
- 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
---
v13: 31oct2022
- 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 crash_prepare_elf64_headers()
crash: prototype change for crash_prepare_elf64_headers()
crash: add generic infrastructure for crash hotplug support
kexec: exclude elfcorehdr from the segment digest
kexec: exclude hot remove cpu from elfcorehdr notes
crash: memory and cpu hotplug sysfs attributes
x86/crash: add x86 crash hotplug support
.../admin-guide/mm/memory-hotplug.rst | 8 +
Documentation/core-api/cpu_hotplug.rst | 18 ++
arch/arm64/kernel/machine_kexec_file.c | 6 +-
arch/powerpc/kexec/file_load_64.c | 2 +-
arch/riscv/kernel/elf_kexec.c | 7 +-
arch/x86/include/asm/kexec.h | 14 +
arch/x86/kernel/crash.c | 110 +++++++-
drivers/base/cpu.c | 14 +
drivers/base/memory.c | 13 +
include/linux/crash_core.h | 8 +
include/linux/kexec.h | 54 +++-
kernel/crash_core.c | 255 ++++++++++++++++++
kernel/kexec_file.c | 105 +-------
13 files changed, 502 insertions(+), 112 deletions(-)
--
2.31.1
^ permalink raw reply [flat|nested] 40+ messages in thread
* [PATCH v13 1/7] crash: move crash_prepare_elf64_headers()
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:35 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:35 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
At the outcome of this patch set, the crash_prepare_elf64_headers()
is utilized on both the kexec_file_load() and kexec_load() paths. As
such, need to move this function out of kexec_file.c and into a
common location crash_core.c.
No functionality change.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
kernel/crash_core.c | 100 ++++++++++++++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 99 -------------------------------------------
2 files changed, 100 insertions(+), 99 deletions(-)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index a0eb4d5cf557..46c160d14045 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 +315,105 @@ 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;
+}
+
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 45637511e0de..f98d1742872b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -1217,102 +1217,3 @@ int crash_exclude_mem_range(struct crash_mem *mem,
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] 40+ messages in thread
* [PATCH v13 1/7] crash: move crash_prepare_elf64_headers()
@ 2022-10-31 19:35 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:35 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
At the outcome of this patch set, the crash_prepare_elf64_headers()
is utilized on both the kexec_file_load() and kexec_load() paths. As
such, need to move this function out of kexec_file.c and into a
common location crash_core.c.
No functionality change.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
kernel/crash_core.c | 100 ++++++++++++++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 99 -------------------------------------------
2 files changed, 100 insertions(+), 99 deletions(-)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index a0eb4d5cf557..46c160d14045 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 +315,105 @@ 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;
+}
+
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 45637511e0de..f98d1742872b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -1217,102 +1217,3 @@ int crash_exclude_mem_range(struct crash_mem *mem,
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] 40+ messages in thread
* [PATCH v13 2/7] crash: prototype change for crash_prepare_elf64_headers()
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:35 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:35 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
From within crash_prepare_elf64_headers() there is a need to
reference the struct kimage hotplug members. As such, this
change passes the struct kimage as a parameter to the
crash_prepare_elf64_headers(). The hotplug members are added
in "crash: add generic infrastructure for crash hotplug support".
This is preparation for later patch, no functionality change.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
arch/arm64/kernel/machine_kexec_file.c | 6 +++---
arch/powerpc/kexec/file_load_64.c | 2 +-
arch/riscv/kernel/elf_kexec.c | 7 ++++---
arch/x86/kernel/crash.c | 2 +-
include/linux/kexec.h | 7 +++++--
kernel/crash_core.c | 4 ++--
6 files changed, 16 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index a11a6e14ba89..2f7b773a83bb 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -39,7 +39,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
return kexec_image_post_load_cleanup_default(image);
}
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+static int prepare_elf_headers(struct kimage *image, void **addr, unsigned long *sz)
{
struct crash_mem *cmem;
unsigned int nr_ranges;
@@ -64,7 +64,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
}
/* Exclude crashkernel region */
- ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+ ret = crash_exclude_mem_range(image, cmem, crashk_res.start, crashk_res.end);
if (ret)
goto out;
@@ -74,7 +74,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
goto out;
}
- ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+ ret = crash_prepare_elf64_headers(image, cmem, true, addr, sz);
out:
kfree(cmem);
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 349a781cea0b..a0af9966a8f0 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -798,7 +798,7 @@ static int load_elfcorehdr_segment(struct kimage *image, struct kexec_buf *kbuf)
goto out;
/* Setup elfcorehdr segment */
- ret = crash_prepare_elf64_headers(cmem, false, &headers, &headers_sz);
+ ret = crash_prepare_elf64_headers(image, cmem, false, &headers, &headers_sz);
if (ret) {
pr_err("Failed to prepare elf headers for the core\n");
goto out;
diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 0cb94992c15b..ffde73228108 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -118,7 +118,8 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
return 0;
}
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+static int prepare_elf_headers(struct kimage *image,
+ void **addr, unsigned long *sz)
{
struct crash_mem *cmem;
unsigned int nr_ranges;
@@ -140,7 +141,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
/* Exclude crashkernel region */
ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
if (!ret)
- ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+ ret = crash_prepare_elf64_headers(image, cmem, true, addr, sz);
out:
kfree(cmem);
@@ -212,7 +213,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
/* Add elfcorehdr */
if (image->type == KEXEC_TYPE_CRASH) {
- ret = prepare_elf_headers(&headers, &headers_sz);
+ ret = prepare_elf_headers(image, &headers, &headers_sz);
if (ret) {
pr_err("Preparing elf core header failed\n");
goto out;
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9730c88530fc..9ceb93c176a6 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -265,7 +265,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
goto out;
/* By default prepare 64bit headers */
- ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
+ ret = crash_prepare_elf64_headers(image, cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
out:
vfree(cmem);
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 41a686996aaa..ebf46c3b8f8b 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -253,8 +253,11 @@ struct crash_mem {
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);
+extern int crash_prepare_elf64_headers(struct kimage *image,
+ struct crash_mem *mem,
+ int need_kernel_map,
+ void **addr,
+ unsigned long *sz);
#ifndef arch_kexec_apply_relocations_add
/*
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 46c160d14045..8c648fd5897a 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -315,8 +315,8 @@ 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)
+int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
+ int need_kernel_map, void **addr, unsigned long *sz)
{
Elf64_Ehdr *ehdr;
Elf64_Phdr *phdr;
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 2/7] crash: prototype change for crash_prepare_elf64_headers()
@ 2022-10-31 19:35 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:35 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
From within crash_prepare_elf64_headers() there is a need to
reference the struct kimage hotplug members. As such, this
change passes the struct kimage as a parameter to the
crash_prepare_elf64_headers(). The hotplug members are added
in "crash: add generic infrastructure for crash hotplug support".
This is preparation for later patch, no functionality change.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
arch/arm64/kernel/machine_kexec_file.c | 6 +++---
arch/powerpc/kexec/file_load_64.c | 2 +-
arch/riscv/kernel/elf_kexec.c | 7 ++++---
arch/x86/kernel/crash.c | 2 +-
include/linux/kexec.h | 7 +++++--
kernel/crash_core.c | 4 ++--
6 files changed, 16 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index a11a6e14ba89..2f7b773a83bb 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -39,7 +39,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
return kexec_image_post_load_cleanup_default(image);
}
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+static int prepare_elf_headers(struct kimage *image, void **addr, unsigned long *sz)
{
struct crash_mem *cmem;
unsigned int nr_ranges;
@@ -64,7 +64,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
}
/* Exclude crashkernel region */
- ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+ ret = crash_exclude_mem_range(image, cmem, crashk_res.start, crashk_res.end);
if (ret)
goto out;
@@ -74,7 +74,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
goto out;
}
- ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+ ret = crash_prepare_elf64_headers(image, cmem, true, addr, sz);
out:
kfree(cmem);
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 349a781cea0b..a0af9966a8f0 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -798,7 +798,7 @@ static int load_elfcorehdr_segment(struct kimage *image, struct kexec_buf *kbuf)
goto out;
/* Setup elfcorehdr segment */
- ret = crash_prepare_elf64_headers(cmem, false, &headers, &headers_sz);
+ ret = crash_prepare_elf64_headers(image, cmem, false, &headers, &headers_sz);
if (ret) {
pr_err("Failed to prepare elf headers for the core\n");
goto out;
diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 0cb94992c15b..ffde73228108 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -118,7 +118,8 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
return 0;
}
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+static int prepare_elf_headers(struct kimage *image,
+ void **addr, unsigned long *sz)
{
struct crash_mem *cmem;
unsigned int nr_ranges;
@@ -140,7 +141,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
/* Exclude crashkernel region */
ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
if (!ret)
- ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+ ret = crash_prepare_elf64_headers(image, cmem, true, addr, sz);
out:
kfree(cmem);
@@ -212,7 +213,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
/* Add elfcorehdr */
if (image->type == KEXEC_TYPE_CRASH) {
- ret = prepare_elf_headers(&headers, &headers_sz);
+ ret = prepare_elf_headers(image, &headers, &headers_sz);
if (ret) {
pr_err("Preparing elf core header failed\n");
goto out;
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9730c88530fc..9ceb93c176a6 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -265,7 +265,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
goto out;
/* By default prepare 64bit headers */
- ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
+ ret = crash_prepare_elf64_headers(image, cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
out:
vfree(cmem);
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 41a686996aaa..ebf46c3b8f8b 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -253,8 +253,11 @@ struct crash_mem {
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);
+extern int crash_prepare_elf64_headers(struct kimage *image,
+ struct crash_mem *mem,
+ int need_kernel_map,
+ void **addr,
+ unsigned long *sz);
#ifndef arch_kexec_apply_relocations_add
/*
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 46c160d14045..8c648fd5897a 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -315,8 +315,8 @@ 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)
+int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
+ int need_kernel_map, void **addr, unsigned long *sz)
{
Elf64_Ehdr *ehdr;
Elf64_Phdr *phdr;
--
2.31.1
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:36 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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
CPU and memory change notifications are received in order to
regenerate the elfcorehdr.
To support cpu hotplug, a callback is registered to capture the
CPUHP_AP_ONLINE_DYN online and offline events via
cpuhp_setup_state_nocalls().
To support memory hotplug, a notifier is registered to capture the
MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier().
The cpu callback and memory notifiers call handle_hotplug_event()
which performs needed tasks and then dispatches the event to the
architecture specific arch_crash_handle_hotplug_event(). During the
process, the kexec_lock is held.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
include/linux/crash_core.h | 8 +++
include/linux/kexec.h | 39 +++++++++++
kernel/crash_core.c | 139 +++++++++++++++++++++++++++++++++++++
3 files changed, 186 insertions(+)
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index de62a722431e..a270f8660538 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -84,4 +84,12 @@ 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_REMOVE_CPU 0
+#define KEXEC_CRASH_HP_ADD_CPU 1
+#define KEXEC_CRASH_HP_REMOVE_MEMORY 2
+#define KEXEC_CRASH_HP_ADD_MEMORY 3
+#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 ebf46c3b8f8b..04ef5172c4ba 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -32,6 +32,7 @@ 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 */
@@ -374,6 +375,13 @@ struct kimage {
struct purgatory_info purgatory_info;
#endif
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
+ bool hotplug_event;
+ unsigned int offlinecpu;
+ bool elfcorehdr_index_valid;
+ int elfcorehdr_index;
+#endif
+
#ifdef CONFIG_IMA_KEXEC
/* Virtual address of IMA measurement buffer for kexec syscall */
void *ima_buffer;
@@ -503,6 +511,37 @@ 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_map_crash_pages
+/*
+ * NOTE: The addresses and sizes passed to this routine have
+ * already been fully aligned on page boundaries. There is no
+ * need for massaging the address or size.
+ */
+static inline void *arch_map_crash_pages(unsigned long paddr,
+ unsigned long size)
+{
+ if (size > 0)
+ return kmap_local_page(pfn_to_page(paddr >> PAGE_SHIFT));
+ else
+ return NULL;
+}
+#endif
+
+#ifndef arch_unmap_crash_pages
+static inline void arch_unmap_crash_pages(void *ptr)
+{
+ if (ptr)
+ kunmap_local(ptr);
+}
+#endif
+
+#ifndef arch_crash_handle_hotplug_event
+static inline void arch_crash_handle_hotplug_event(struct kimage *image,
+ unsigned int hp_action)
+{
+}
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 8c648fd5897a..3a0ed4168fcd 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;
@@ -612,3 +615,139 @@ static int __init crash_save_vmcoreinfo_init(void)
}
subsys_initcall(crash_save_vmcoreinfo_init);
+
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+/*
+ * To accurately reflect hot un/plug changes, 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 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, it is wiped to zero, so
+ * the elfcorehdr_index_valid defaults to false. 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_valid) {
+ unsigned long mem, memsz;
+ unsigned char *ptr;
+ unsigned int n;
+
+ for (n = 0; n < image->nr_segments; n++) {
+ mem = image->segment[n].mem;
+ memsz = image->segment[n].memsz;
+ ptr = arch_map_crash_pages(mem, memsz);
+ if (ptr) {
+ /* The segment containing elfcorehdr */
+ if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
+ image->elfcorehdr_index = (int)n;
+ image->elfcorehdr_index_valid = true;
+ }
+ }
+ arch_unmap_crash_pages((void *)ptr);
+ }
+ }
+
+ if (!image->elfcorehdr_index_valid) {
+ pr_err("unable to locate elfcorehdr segment");
+ goto out;
+ }
+
+ /* Needed in order for the segments to be updated */
+ arch_kexec_unprotect_crashkres();
+
+ /* Flag to differentiate between normal load and hotplug */
+ image->hotplug_event = true;
+
+ /* Now invoke arch-specific update handler */
+ arch_crash_handle_hotplug_event(image, hp_action);
+
+ /* No longer handling a hotplug event */
+ image->hotplug_event = false;
+
+ /* 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:
+ handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+
+ case MEM_OFFLINE:
+ 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)
+{
+ handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
+ return 0;
+}
+
+static int crash_cpuhp_offline(unsigned int cpu)
+{
+ 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_AP_ONLINE_DYN,
+ "crash/cpuhp",
+ crash_cpuhp_online,
+ crash_cpuhp_offline);
+
+ return result;
+}
+
+subsys_initcall(crash_hotplug_init);
+#endif
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support
@ 2022-10-31 19:36 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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
CPU and memory change notifications are received in order to
regenerate the elfcorehdr.
To support cpu hotplug, a callback is registered to capture the
CPUHP_AP_ONLINE_DYN online and offline events via
cpuhp_setup_state_nocalls().
To support memory hotplug, a notifier is registered to capture the
MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier().
The cpu callback and memory notifiers call handle_hotplug_event()
which performs needed tasks and then dispatches the event to the
architecture specific arch_crash_handle_hotplug_event(). During the
process, the kexec_lock is held.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
include/linux/crash_core.h | 8 +++
include/linux/kexec.h | 39 +++++++++++
kernel/crash_core.c | 139 +++++++++++++++++++++++++++++++++++++
3 files changed, 186 insertions(+)
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index de62a722431e..a270f8660538 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -84,4 +84,12 @@ 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_REMOVE_CPU 0
+#define KEXEC_CRASH_HP_ADD_CPU 1
+#define KEXEC_CRASH_HP_REMOVE_MEMORY 2
+#define KEXEC_CRASH_HP_ADD_MEMORY 3
+#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 ebf46c3b8f8b..04ef5172c4ba 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -32,6 +32,7 @@ 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 */
@@ -374,6 +375,13 @@ struct kimage {
struct purgatory_info purgatory_info;
#endif
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
+ bool hotplug_event;
+ unsigned int offlinecpu;
+ bool elfcorehdr_index_valid;
+ int elfcorehdr_index;
+#endif
+
#ifdef CONFIG_IMA_KEXEC
/* Virtual address of IMA measurement buffer for kexec syscall */
void *ima_buffer;
@@ -503,6 +511,37 @@ 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_map_crash_pages
+/*
+ * NOTE: The addresses and sizes passed to this routine have
+ * already been fully aligned on page boundaries. There is no
+ * need for massaging the address or size.
+ */
+static inline void *arch_map_crash_pages(unsigned long paddr,
+ unsigned long size)
+{
+ if (size > 0)
+ return kmap_local_page(pfn_to_page(paddr >> PAGE_SHIFT));
+ else
+ return NULL;
+}
+#endif
+
+#ifndef arch_unmap_crash_pages
+static inline void arch_unmap_crash_pages(void *ptr)
+{
+ if (ptr)
+ kunmap_local(ptr);
+}
+#endif
+
+#ifndef arch_crash_handle_hotplug_event
+static inline void arch_crash_handle_hotplug_event(struct kimage *image,
+ unsigned int hp_action)
+{
+}
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 8c648fd5897a..3a0ed4168fcd 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;
@@ -612,3 +615,139 @@ static int __init crash_save_vmcoreinfo_init(void)
}
subsys_initcall(crash_save_vmcoreinfo_init);
+
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
+#undef pr_fmt
+#define pr_fmt(fmt) "crash hp: " fmt
+/*
+ * To accurately reflect hot un/plug changes, 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 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, it is wiped to zero, so
+ * the elfcorehdr_index_valid defaults to false. 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_valid) {
+ unsigned long mem, memsz;
+ unsigned char *ptr;
+ unsigned int n;
+
+ for (n = 0; n < image->nr_segments; n++) {
+ mem = image->segment[n].mem;
+ memsz = image->segment[n].memsz;
+ ptr = arch_map_crash_pages(mem, memsz);
+ if (ptr) {
+ /* The segment containing elfcorehdr */
+ if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
+ image->elfcorehdr_index = (int)n;
+ image->elfcorehdr_index_valid = true;
+ }
+ }
+ arch_unmap_crash_pages((void *)ptr);
+ }
+ }
+
+ if (!image->elfcorehdr_index_valid) {
+ pr_err("unable to locate elfcorehdr segment");
+ goto out;
+ }
+
+ /* Needed in order for the segments to be updated */
+ arch_kexec_unprotect_crashkres();
+
+ /* Flag to differentiate between normal load and hotplug */
+ image->hotplug_event = true;
+
+ /* Now invoke arch-specific update handler */
+ arch_crash_handle_hotplug_event(image, hp_action);
+
+ /* No longer handling a hotplug event */
+ image->hotplug_event = false;
+
+ /* 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:
+ handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
+ KEXEC_CRASH_HP_INVALID_CPU);
+ break;
+
+ case MEM_OFFLINE:
+ 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)
+{
+ handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
+ return 0;
+}
+
+static int crash_cpuhp_offline(unsigned int cpu)
+{
+ 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_AP_ONLINE_DYN,
+ "crash/cpuhp",
+ crash_cpuhp_online,
+ crash_cpuhp_offline);
+
+ return result;
+}
+
+subsys_initcall(crash_hotplug_init);
+#endif
--
2.31.1
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 4/7] kexec: exclude elfcorehdr from the segment digest
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:36 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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.
Since hotplug events cause changes to the elfcorehdr, purgatory
integrity checking fails (at crash time, and no kdump created).
As a result, this change explicitly excludes the elfcorehdr segment
from the list of segments used to create the digest. By doing so,
this permits changes to the elfcorehdr in response to hotplug events,
without having to also reload purgatory due to the change to the
digest.
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 f98d1742872b..4d3451cf9f0c 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;
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU) || IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
+ /* Exclude elfcorehdr segment to allow future changes via hotplug */
+ if (image->elfcorehdr_index_valid && (j == image->elfcorehdr_index))
+ continue;
+ }
+
ksegment = &image->segment[i];
/*
* Skip purgatory as it will be modified once we put digest
--
2.31.1
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 4/7] kexec: exclude elfcorehdr from the segment digest
@ 2022-10-31 19:36 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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.
Since hotplug events cause changes to the elfcorehdr, purgatory
integrity checking fails (at crash time, and no kdump created).
As a result, this change explicitly excludes the elfcorehdr segment
from the list of segments used to create the digest. By doing so,
this permits changes to the elfcorehdr in response to hotplug events,
without having to also reload purgatory due to the change to the
digest.
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 f98d1742872b..4d3451cf9f0c 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;
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU) || IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
+ /* Exclude elfcorehdr segment to allow future changes via hotplug */
+ if (image->elfcorehdr_index_valid && (j == image->elfcorehdr_index))
+ continue;
+ }
+
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] 40+ messages in thread
* [PATCH v13 5/7] kexec: exclude hot remove cpu from elfcorehdr notes
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:36 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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
Due to use of CPUHP_AP_ONLINE_DYN, upon CPU unplug, the CPU is
still in the for_each_present_cpu() list when within the
handle_hotplug_event(). Thus the CPU must be explicitly excluded
when building the new list of CPUs.
This change identifies in handle_hotplug_event() the CPU to be
excluded, and the check for excluding the CPU in
crash_prepare_elf64_headers().
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
kernel/crash_core.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 3a0ed4168fcd..bca1b198d9e5 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -366,6 +366,12 @@ int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
/* Prepare one phdr of type PT_NOTE for each present CPU */
for_each_present_cpu(cpu) {
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ /* Skip the soon-to-be offlined cpu */
+ if (image->hotplug_event && (cpu == image->offlinecpu))
+ continue;
+ }
+
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;
@@ -684,6 +690,16 @@ static void handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
/* Flag to differentiate between normal load and hotplug */
image->hotplug_event = true;
+ /*
+ * Due to use of CPUHP_AP_ONLINE_DYN, upon unplug and during
+ * this callback, the CPU is still in the for_each_present_cpu()
+ * list. Must explicitly look to exclude this CPU when building
+ * new list.
+ */
+ image->offlinecpu =
+ (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) ?
+ cpu : KEXEC_CRASH_HP_INVALID_CPU;
+
/* Now invoke arch-specific update handler */
arch_crash_handle_hotplug_event(image, hp_action);
--
2.31.1
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 5/7] kexec: exclude hot remove cpu from elfcorehdr notes
@ 2022-10-31 19:36 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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
Due to use of CPUHP_AP_ONLINE_DYN, upon CPU unplug, the CPU is
still in the for_each_present_cpu() list when within the
handle_hotplug_event(). Thus the CPU must be explicitly excluded
when building the new list of CPUs.
This change identifies in handle_hotplug_event() the CPU to be
excluded, and the check for excluding the CPU in
crash_prepare_elf64_headers().
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
kernel/crash_core.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 3a0ed4168fcd..bca1b198d9e5 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -366,6 +366,12 @@ int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
/* Prepare one phdr of type PT_NOTE for each present CPU */
for_each_present_cpu(cpu) {
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ /* Skip the soon-to-be offlined cpu */
+ if (image->hotplug_event && (cpu == image->offlinecpu))
+ continue;
+ }
+
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;
@@ -684,6 +690,16 @@ static void handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
/* Flag to differentiate between normal load and hotplug */
image->hotplug_event = true;
+ /*
+ * Due to use of CPUHP_AP_ONLINE_DYN, upon unplug and during
+ * this callback, the CPU is still in the for_each_present_cpu()
+ * list. Must explicitly look to exclude this CPU when building
+ * new list.
+ */
+ image->offlinecpu =
+ (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) ?
+ cpu : KEXEC_CRASH_HP_INVALID_CPU;
+
/* Now invoke arch-specific update handler */
arch_crash_handle_hotplug_event(image, hp_action);
--
2.31.1
^ permalink raw reply related [flat|nested] 40+ messages in thread
* [PATCH v13 6/7] crash: memory and cpu hotplug sysfs attributes
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:36 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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 fail 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 9aa0da991cfb..226be3134ffe 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -483,6 +483,16 @@ 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
@@ -881,6 +891,9 @@ 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 04ef5172c4ba..e2dbbcbf37dc 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -542,6 +542,14 @@ 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] 40+ messages in thread
* [PATCH v13 6/7] crash: memory and cpu hotplug sysfs attributes
@ 2022-10-31 19:36 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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 fail 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 9aa0da991cfb..226be3134ffe 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -483,6 +483,16 @@ 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
@@ -881,6 +891,9 @@ 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 04ef5172c4ba..e2dbbcbf37dc 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -542,6 +542,14 @@ 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] 40+ messages in thread
* [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-10-31 19:35 ` Eric DeVolder
@ 2022-10-31 19:36 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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, the crash elfcorehdr, which
describes the CPUs and memory in the system, must also be updated.
A new elfcorehdr is generated from the available CPUs and memory
into a buffer, and then installed over the top of the existing
elfcorehdr. The segment containing the elfcorehdr is identified
at run time in crash_core:handle_hotplug_event(), which works for
both the kexec_load() and kexec_file_load() syscalls.
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.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/include/asm/kexec.h | 14 +++++
arch/x86/kernel/crash.c | 108 ++++++++++++++++++++++++++++++++++-
2 files changed, 119 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index a3760ca796aa..d72d347bd1d3 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -212,6 +212,20 @@ typedef void crash_vmclear_fn(void);
extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
extern void kdump_nmi_shootdown_cpus(void);
+void arch_crash_handle_hotplug_event(struct kimage *image,
+ unsigned int hp_action);
+#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 /* __ASSEMBLY__ */
#endif /* _ASM_X86_KEXEC_H */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9ceb93c176a6..2687acf28977 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;
@@ -394,10 +409,30 @@ int crash_load_segments(struct kimage *image)
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;
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU) || IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
+ /* Ensure elfcorehdr segment large enough for hotplug changes */
+ unsigned long pnum = 2; /* VMCOREINFO and kernel_map */
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+ pnum += CONFIG_NR_CPUS_DEFAULT;
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ pnum += CRASH_MAX_MEMORY_RANGES;
+ if (pnum < (unsigned long)PN_XNUM) {
+ kbuf.memsz = pnum * sizeof(Elf64_Phdr);
+ kbuf.memsz += sizeof(Elf64_Ehdr);
+ image->elfcorehdr_index = image->nr_segments;
+ image->elfcorehdr_index_valid = true;
+ /* 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);
+ }
+ }
- kbuf.memsz = kbuf.bufsz;
kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
ret = kexec_add_buffer(&kbuf);
@@ -412,3 +447,70 @@ int crash_load_segments(struct kimage *image)
return ret;
}
#endif /* CONFIG_KEXEC_FILE */
+
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_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
+ * @hp_action: the hot un/plug action being handled
+ *
+ * To accurately reflect hot un/plug changes, 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,
+ unsigned int hp_action)
+{
+ unsigned long mem, memsz;
+ unsigned long elfsz = 0;
+ void *elfbuf = NULL;
+ void *ptr;
+
+ /*
+ * Create the new elfcorehdr reflecting the changes to CPU and/or
+ * memory resources.
+ */
+ if (prepare_elf_headers(image, &elfbuf, &elfsz)) {
+ 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.
+ */
+ ptr = arch_map_crash_pages(mem, memsz);
+ if (ptr) {
+ /*
+ * Temporarily invalidate the crash image while the
+ * elfcorehdr is updated.
+ */
+ xchg(&kexec_crash_image, NULL);
+ memcpy_flushcache(ptr, elfbuf, elfsz);
+ xchg(&kexec_crash_image, image);
+ arch_unmap_crash_pages(ptr);
+ pr_debug("updated elfcorehdr\n");
+ } else {
+ pr_err("updating elfcorehdr failed\n");
+ }
+
+out:
+ if (elfbuf)
+ 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] 40+ messages in thread
* [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-10-31 19:36 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-10-31 19:36 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, the crash elfcorehdr, which
describes the CPUs and memory in the system, must also be updated.
A new elfcorehdr is generated from the available CPUs and memory
into a buffer, and then installed over the top of the existing
elfcorehdr. The segment containing the elfcorehdr is identified
at run time in crash_core:handle_hotplug_event(), which works for
both the kexec_load() and kexec_file_load() syscalls.
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.
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/include/asm/kexec.h | 14 +++++
arch/x86/kernel/crash.c | 108 ++++++++++++++++++++++++++++++++++-
2 files changed, 119 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index a3760ca796aa..d72d347bd1d3 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -212,6 +212,20 @@ typedef void crash_vmclear_fn(void);
extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
extern void kdump_nmi_shootdown_cpus(void);
+void arch_crash_handle_hotplug_event(struct kimage *image,
+ unsigned int hp_action);
+#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 /* __ASSEMBLY__ */
#endif /* _ASM_X86_KEXEC_H */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9ceb93c176a6..2687acf28977 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;
@@ -394,10 +409,30 @@ int crash_load_segments(struct kimage *image)
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;
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU) || IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
+ /* Ensure elfcorehdr segment large enough for hotplug changes */
+ unsigned long pnum = 2; /* VMCOREINFO and kernel_map */
+
+ if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+ pnum += CONFIG_NR_CPUS_DEFAULT;
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ pnum += CRASH_MAX_MEMORY_RANGES;
+ if (pnum < (unsigned long)PN_XNUM) {
+ kbuf.memsz = pnum * sizeof(Elf64_Phdr);
+ kbuf.memsz += sizeof(Elf64_Ehdr);
+ image->elfcorehdr_index = image->nr_segments;
+ image->elfcorehdr_index_valid = true;
+ /* 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);
+ }
+ }
- kbuf.memsz = kbuf.bufsz;
kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
ret = kexec_add_buffer(&kbuf);
@@ -412,3 +447,70 @@ int crash_load_segments(struct kimage *image)
return ret;
}
#endif /* CONFIG_KEXEC_FILE */
+
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_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
+ * @hp_action: the hot un/plug action being handled
+ *
+ * To accurately reflect hot un/plug changes, 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,
+ unsigned int hp_action)
+{
+ unsigned long mem, memsz;
+ unsigned long elfsz = 0;
+ void *elfbuf = NULL;
+ void *ptr;
+
+ /*
+ * Create the new elfcorehdr reflecting the changes to CPU and/or
+ * memory resources.
+ */
+ if (prepare_elf_headers(image, &elfbuf, &elfsz)) {
+ 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.
+ */
+ ptr = arch_map_crash_pages(mem, memsz);
+ if (ptr) {
+ /*
+ * Temporarily invalidate the crash image while the
+ * elfcorehdr is updated.
+ */
+ xchg(&kexec_crash_image, NULL);
+ memcpy_flushcache(ptr, elfbuf, elfsz);
+ xchg(&kexec_crash_image, image);
+ arch_unmap_crash_pages(ptr);
+ pr_debug("updated elfcorehdr\n");
+ } else {
+ pr_err("updating elfcorehdr failed\n");
+ }
+
+out:
+ if (elfbuf)
+ vfree(elfbuf);
+}
+#endif
--
2.31.1
^ permalink raw reply related [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-10-31 19:36 ` Eric DeVolder
@ 2022-10-31 21:04 ` Borislav Petkov
-1 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-10-31 21:04 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Mon, Oct 31, 2022 at 03:36:04PM -0400, Eric DeVolder wrote:
> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
What happened to that here:
https://lore.kernel.org/r/Y1e85gqB3kzlx7qL@zn.tnic
?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-10-31 21:04 ` Borislav Petkov
0 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-10-31 21:04 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Mon, Oct 31, 2022 at 03:36:04PM -0400, Eric DeVolder wrote:
> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
What happened to that here:
https://lore.kernel.org/r/Y1e85gqB3kzlx7qL@zn.tnic
?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-10-31 21:04 ` Borislav Petkov
@ 2022-11-01 15:45 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-01 15:45 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 10/31/22 16:04, Borislav Petkov wrote:
> On Mon, Oct 31, 2022 at 03:36:04PM -0400, Eric DeVolder wrote:
>> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>
> What happened to that here:
>
> https://lore.kernel.org/r/Y1e85gqB3kzlx7qL@zn.tnic
>
> ?
>
When I was evaluating the suggestions, I realized that that particular ifdiffery was now used in
only 3 locations, twice in kernel/crash_core.c and once in x86 crash.c.
With that realization, and the fact that we just jettisoned CONFIG_CRASH_MAX_MEMORY_RANGES for a
#define, it seemed that there wasn't a compelling need to replace the HOTPLUG_CPU || MEMORY_HOTPLUG
with a new CRASH_HOTPLUG Kconfig item.
As I'm re-reading that message, I suspect now the preference is to just to strike this ifdiffery
line in this file and have the code always present?
If the preference is actually for CRASH_HOTPLUG, then let me know.
Thanks!
eric
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-01 15:45 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-01 15:45 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 10/31/22 16:04, Borislav Petkov wrote:
> On Mon, Oct 31, 2022 at 03:36:04PM -0400, Eric DeVolder wrote:
>> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>
> What happened to that here:
>
> https://lore.kernel.org/r/Y1e85gqB3kzlx7qL@zn.tnic
>
> ?
>
When I was evaluating the suggestions, I realized that that particular ifdiffery was now used in
only 3 locations, twice in kernel/crash_core.c and once in x86 crash.c.
With that realization, and the fact that we just jettisoned CONFIG_CRASH_MAX_MEMORY_RANGES for a
#define, it seemed that there wasn't a compelling need to replace the HOTPLUG_CPU || MEMORY_HOTPLUG
with a new CRASH_HOTPLUG Kconfig item.
As I'm re-reading that message, I suspect now the preference is to just to strike this ifdiffery
line in this file and have the code always present?
If the preference is actually for CRASH_HOTPLUG, then let me know.
Thanks!
eric
_______________________________________________
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kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-01 15:45 ` Eric DeVolder
@ 2022-11-02 9:26 ` Borislav Petkov
-1 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 9:26 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Tue, Nov 01, 2022 at 10:45:00AM -0500, Eric DeVolder wrote:
> As I'm re-reading that message, I suspect now the preference is to just to
> strike this ifdiffery line in this file and have the code always present?
>
> If the preference is actually for CRASH_HOTPLUG, then let me know.
Well, it is this part:
"But on a plain simple laptop or workstation which has CPU hotplug,
would it make sense for the crash ranges to get updated too when CPUs
are offlined?
If so, I think you want this code present there too, without a Kconfig
item."
IOW, if this thing doesn't make sense to have on the majority of
machines out there - and memory hotplug machines are not the majority -
then it should be behind a Kconfig item which is default off and gets
enabled only when the user selects crash and memory hotplug...
I'd say.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 9:26 ` Borislav Petkov
0 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 9:26 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Tue, Nov 01, 2022 at 10:45:00AM -0500, Eric DeVolder wrote:
> As I'm re-reading that message, I suspect now the preference is to just to
> strike this ifdiffery line in this file and have the code always present?
>
> If the preference is actually for CRASH_HOTPLUG, then let me know.
Well, it is this part:
"But on a plain simple laptop or workstation which has CPU hotplug,
would it make sense for the crash ranges to get updated too when CPUs
are offlined?
If so, I think you want this code present there too, without a Kconfig
item."
IOW, if this thing doesn't make sense to have on the majority of
machines out there - and memory hotplug machines are not the majority -
then it should be behind a Kconfig item which is default off and gets
enabled only when the user selects crash and memory hotplug...
I'd say.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 9:26 ` Borislav Petkov
@ 2022-11-02 14:55 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-02 14:55 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 04:26, Borislav Petkov wrote:
> On Tue, Nov 01, 2022 at 10:45:00AM -0500, Eric DeVolder wrote:
>> As I'm re-reading that message, I suspect now the preference is to just to
>> strike this ifdiffery line in this file and have the code always present?
>>
>> If the preference is actually for CRASH_HOTPLUG, then let me know.
>
> Well, it is this part:
>
> "But on a plain simple laptop or workstation which has CPU hotplug,
> would it make sense for the crash ranges to get updated too when CPUs
> are offlined?
Yes, it does.
>
> If so, I think you want this code present there too, without a Kconfig
> item."
Ah, ok.
>
> IOW, if this thing doesn't make sense to have on the majority of
> machines out there - and memory hotplug machines are not the majority -
> then it should be behind a Kconfig item which is default off and gets
> enabled only when the user selects crash and memory hotplug...
>
> I'd say.
>
Ok, I'll will remove the ifdef line/pair.
Thanks!
eric
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 14:55 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-02 14:55 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 04:26, Borislav Petkov wrote:
> On Tue, Nov 01, 2022 at 10:45:00AM -0500, Eric DeVolder wrote:
>> As I'm re-reading that message, I suspect now the preference is to just to
>> strike this ifdiffery line in this file and have the code always present?
>>
>> If the preference is actually for CRASH_HOTPLUG, then let me know.
>
> Well, it is this part:
>
> "But on a plain simple laptop or workstation which has CPU hotplug,
> would it make sense for the crash ranges to get updated too when CPUs
> are offlined?
Yes, it does.
>
> If so, I think you want this code present there too, without a Kconfig
> item."
Ah, ok.
>
> IOW, if this thing doesn't make sense to have on the majority of
> machines out there - and memory hotplug machines are not the majority -
> then it should be behind a Kconfig item which is default off and gets
> enabled only when the user selects crash and memory hotplug...
>
> I'd say.
>
Ok, I'll will remove the ifdef line/pair.
Thanks!
eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 14:55 ` Eric DeVolder
@ 2022-11-02 16:19 ` Borislav Petkov
-1 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 16:19 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 02, 2022 at 09:55:06AM -0500, Eric DeVolder wrote:
> > "But on a plain simple laptop or workstation which has CPU hotplug,
> > would it make sense for the crash ranges to get updated too when CPUs
> > are offlined?
>
> Yes, it does.
Why?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 16:19 ` Borislav Petkov
0 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 16:19 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 02, 2022 at 09:55:06AM -0500, Eric DeVolder wrote:
> > "But on a plain simple laptop or workstation which has CPU hotplug,
> > would it make sense for the crash ranges to get updated too when CPUs
> > are offlined?
>
> Yes, it does.
Why?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 16:19 ` Borislav Petkov
@ 2022-11-02 16:54 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-02 16:54 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 11:19, Borislav Petkov wrote:
> On Wed, Nov 02, 2022 at 09:55:06AM -0500, Eric DeVolder wrote:
>>> "But on a plain simple laptop or workstation which has CPU hotplug,
>>> would it make sense for the crash ranges to get updated too when CPUs
>>> are offlined?
>>
>> Yes, it does.
>
> Why?
>
Technically the answer is no; cpu hotplug events are independent of memory hotplug events, but both
are written into the elfcorehdr, so in reality yes... The elfcorehdr contains a single list of Phdrs
describing CPUs and crash memory ranges; the entire list is re-written on a hotplug change.
Eric
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 16:54 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-02 16:54 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 11:19, Borislav Petkov wrote:
> On Wed, Nov 02, 2022 at 09:55:06AM -0500, Eric DeVolder wrote:
>>> "But on a plain simple laptop or workstation which has CPU hotplug,
>>> would it make sense for the crash ranges to get updated too when CPUs
>>> are offlined?
>>
>> Yes, it does.
>
> Why?
>
Technically the answer is no; cpu hotplug events are independent of memory hotplug events, but both
are written into the elfcorehdr, so in reality yes... The elfcorehdr contains a single list of Phdrs
describing CPUs and crash memory ranges; the entire list is re-written on a hotplug change.
Eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 16:54 ` Eric DeVolder
@ 2022-11-02 18:49 ` Borislav Petkov
-1 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 18:49 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 02, 2022 at 11:54:08AM -0500, Eric DeVolder wrote:
> Technically the answer is no; cpu hotplug events are independent of memory
> hotplug events, but both are written into the elfcorehdr, so in reality
> yes... The elfcorehdr contains a single list of Phdrs describing CPUs and
> crash memory ranges; the entire list is re-written on a hotplug change.
Then technically also yes. Otherwise your crash information will contain
wrong CPU numbers.
How has that not been a problem until now...?
I.e., offline a bunch of CPUs and then cause a crash dump.
Hmm.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 18:49 ` Borislav Petkov
0 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 18:49 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 02, 2022 at 11:54:08AM -0500, Eric DeVolder wrote:
> Technically the answer is no; cpu hotplug events are independent of memory
> hotplug events, but both are written into the elfcorehdr, so in reality
> yes... The elfcorehdr contains a single list of Phdrs describing CPUs and
> crash memory ranges; the entire list is re-written on a hotplug change.
Then technically also yes. Otherwise your crash information will contain
wrong CPU numbers.
How has that not been a problem until now...?
I.e., offline a bunch of CPUs and then cause a crash dump.
Hmm.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 18:49 ` Borislav Petkov
@ 2022-11-02 18:57 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-02 18:57 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 13:49, Borislav Petkov wrote:
> On Wed, Nov 02, 2022 at 11:54:08AM -0500, Eric DeVolder wrote:
>> Technically the answer is no; cpu hotplug events are independent of memory
>> hotplug events, but both are written into the elfcorehdr, so in reality
>> yes... The elfcorehdr contains a single list of Phdrs describing CPUs and
>> crash memory ranges; the entire list is re-written on a hotplug change.
>
> Then technically also yes. Otherwise your crash information will contain
> wrong CPU numbers.
>
> How has that not been a problem until now...?
>
> I.e., offline a bunch of CPUs and then cause a crash dump.
>
> Hmm.
>
There is a solution for updating the elfcorehdr today, for when say a bunch of CPUs are offlined. It
is done via userspace udev rules to do a unload-then-reload of the entire crash kernel system
(kernel, initrd, purgatory, boot_params, and of course elfcorehdr). This performs extremely poorly
in highly dynamic hotplug situations (such as when adding alot of memory to a vm), and thus the
attempt at this solution.
But I sense I missing your point?
Thanks!
eric
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 18:57 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-02 18:57 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 13:49, Borislav Petkov wrote:
> On Wed, Nov 02, 2022 at 11:54:08AM -0500, Eric DeVolder wrote:
>> Technically the answer is no; cpu hotplug events are independent of memory
>> hotplug events, but both are written into the elfcorehdr, so in reality
>> yes... The elfcorehdr contains a single list of Phdrs describing CPUs and
>> crash memory ranges; the entire list is re-written on a hotplug change.
>
> Then technically also yes. Otherwise your crash information will contain
> wrong CPU numbers.
>
> How has that not been a problem until now...?
>
> I.e., offline a bunch of CPUs and then cause a crash dump.
>
> Hmm.
>
There is a solution for updating the elfcorehdr today, for when say a bunch of CPUs are offlined. It
is done via userspace udev rules to do a unload-then-reload of the entire crash kernel system
(kernel, initrd, purgatory, boot_params, and of course elfcorehdr). This performs extremely poorly
in highly dynamic hotplug situations (such as when adding alot of memory to a vm), and thus the
attempt at this solution.
But I sense I missing your point?
Thanks!
eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 18:57 ` Eric DeVolder
@ 2022-11-02 19:22 ` Borislav Petkov
-1 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 19:22 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 02, 2022 at 01:57:14PM -0500, Eric DeVolder wrote:
> But I sense I missing your point?
No no, you're spot on. So moving that into the kernel and making it more
robust is always a good thing.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-02 19:22 ` Borislav Petkov
0 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-02 19:22 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 02, 2022 at 01:57:14PM -0500, Eric DeVolder wrote:
> But I sense I missing your point?
No no, you're spot on. So moving that into the kernel and making it more
robust is always a good thing.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-02 9:26 ` Borislav Petkov
@ 2022-11-09 15:48 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-09 15:48 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 04:26, Borislav Petkov wrote:
> On Tue, Nov 01, 2022 at 10:45:00AM -0500, Eric DeVolder wrote:
>> As I'm re-reading that message, I suspect now the preference is to just to
>> strike this ifdiffery line in this file and have the code always present?
>>
>> If the preference is actually for CRASH_HOTPLUG, then let me know.
>
> Well, it is this part:
>
> "But on a plain simple laptop or workstation which has CPU hotplug,
> would it make sense for the crash ranges to get updated too when CPUs
> are offlined?
>
> If so, I think you want this code present there too, without a Kconfig
> item."
>
> IOW, if this thing doesn't make sense to have on the majority of
> machines out there - and memory hotplug machines are not the majority -
> then it should be behind a Kconfig item which is default off and gets
> enabled only when the user selects crash and memory hotplug...
>
> I'd say.
>
Boris,
I apologize for the delay in responding, I've been away for the past week.
I'm re-reading the thread on this topic, and I apologize for backing up a bit,
but as I read the last paragraph again, your contention is that the bit of
code in this file *should* be behind a Kconfig item, and default to off, as
"memory hotplug machines are not the majority".
Does this mean then that I need to introduce CRASH_HOTPLUG again, so it can be
default off?
Examining arch/x86/configs/x86_64_defconfig, neither HOTPLUG_CPU or MEMORY_HOTPLUG are present, but
CONFIG_SMP=y.
And in examining arch/x86/Kconfig, I see:
config HOTPLUG_CPU
def_bool y
depends on SMP
which then defaults HOTPLUG_CPU to on and thus this code/ifdef in question.
And as a reminder, the '#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)' shows up
in only three locations: include/linux/kexec.h, kernel/crash_core.c and arch/x86/kernel/crash.c.
And we resolved in this thread last week that this patch series is useful for cpu and/or memory hotplug.
So at this point, I'm still not sure if you want the ifdef line:
- removed altogether
- transitioned to CRASH_HOTPLUG
- leave as is
If I could get clarity on that, that would be much appreciated!
Thanks!
eric
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-09 15:48 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-09 15:48 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/2/22 04:26, Borislav Petkov wrote:
> On Tue, Nov 01, 2022 at 10:45:00AM -0500, Eric DeVolder wrote:
>> As I'm re-reading that message, I suspect now the preference is to just to
>> strike this ifdiffery line in this file and have the code always present?
>>
>> If the preference is actually for CRASH_HOTPLUG, then let me know.
>
> Well, it is this part:
>
> "But on a plain simple laptop or workstation which has CPU hotplug,
> would it make sense for the crash ranges to get updated too when CPUs
> are offlined?
>
> If so, I think you want this code present there too, without a Kconfig
> item."
>
> IOW, if this thing doesn't make sense to have on the majority of
> machines out there - and memory hotplug machines are not the majority -
> then it should be behind a Kconfig item which is default off and gets
> enabled only when the user selects crash and memory hotplug...
>
> I'd say.
>
Boris,
I apologize for the delay in responding, I've been away for the past week.
I'm re-reading the thread on this topic, and I apologize for backing up a bit,
but as I read the last paragraph again, your contention is that the bit of
code in this file *should* be behind a Kconfig item, and default to off, as
"memory hotplug machines are not the majority".
Does this mean then that I need to introduce CRASH_HOTPLUG again, so it can be
default off?
Examining arch/x86/configs/x86_64_defconfig, neither HOTPLUG_CPU or MEMORY_HOTPLUG are present, but
CONFIG_SMP=y.
And in examining arch/x86/Kconfig, I see:
config HOTPLUG_CPU
def_bool y
depends on SMP
which then defaults HOTPLUG_CPU to on and thus this code/ifdef in question.
And as a reminder, the '#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)' shows up
in only three locations: include/linux/kexec.h, kernel/crash_core.c and arch/x86/kernel/crash.c.
And we resolved in this thread last week that this patch series is useful for cpu and/or memory hotplug.
So at this point, I'm still not sure if you want the ifdef line:
- removed altogether
- transitioned to CRASH_HOTPLUG
- leave as is
If I could get clarity on that, that would be much appreciated!
Thanks!
eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-09 15:48 ` Eric DeVolder
@ 2022-11-09 21:31 ` Borislav Petkov
-1 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-09 21:31 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 09, 2022 at 09:48:33AM -0600, Eric DeVolder wrote:
> ...
> which then defaults HOTPLUG_CPU to on and thus this code/ifdef in question.
defconfig can sometimes lag reality. In this case, the majority of
machines have SMP=y because the majority of machines out there are,
well, multicore.
> So at this point, I'm still not sure if you want the ifdef line:
> - removed altogether
> - transitioned to CRASH_HOTPLUG
> - leave as is
So let's think out loud:
* the majority of machines will have CONFIG_HOTPLUG_CPU=y because
they're SMP machines and we want the elfcorehdr updates to happen when
CPUs get offlined or onlined.
CONFIG_MEMORY_HOTPLUG is most likely going to be =n on the majority of
machines out there.
(Note how the deciding factor for all this is what would make sense on
the prevailing majority of machines out there.)
And memory hotplug will be off for the simple reason that not so many
machines have memory hotplug hardware capability.
Which then means, IMHO, this functionality should be separate: have a
CPU hotplug callback and a memory hotplug callback.
And you kinda do that in
Subject: [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support
but then this all calls into a single handle_hotplug_event() and that
hp_action doesn't really matter.
It is used in the call to
arch_crash_handle_hotplug_event(image, hp_action);
but that hp_action argument is unused in the x86 version.
IOW, you can do this callback regardless whether it is a CPU or memory
hotplug event.
So thinking about it, a single CONFIG_CRASH_HOTPLUG which unifies those
CPU and memory hotplug callback functionality makes most sense to me.
Because you don't really differentiate between the two in the callback
actions.
Anyway, this is how I see it from here. I could very well be missing an
aspect, of course.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-09 21:31 ` Borislav Petkov
0 siblings, 0 replies; 40+ messages in thread
From: Borislav Petkov @ 2022-11-09 21:31 UTC (permalink / raw)
To: Eric DeVolder
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On Wed, Nov 09, 2022 at 09:48:33AM -0600, Eric DeVolder wrote:
> ...
> which then defaults HOTPLUG_CPU to on and thus this code/ifdef in question.
defconfig can sometimes lag reality. In this case, the majority of
machines have SMP=y because the majority of machines out there are,
well, multicore.
> So at this point, I'm still not sure if you want the ifdef line:
> - removed altogether
> - transitioned to CRASH_HOTPLUG
> - leave as is
So let's think out loud:
* the majority of machines will have CONFIG_HOTPLUG_CPU=y because
they're SMP machines and we want the elfcorehdr updates to happen when
CPUs get offlined or onlined.
CONFIG_MEMORY_HOTPLUG is most likely going to be =n on the majority of
machines out there.
(Note how the deciding factor for all this is what would make sense on
the prevailing majority of machines out there.)
And memory hotplug will be off for the simple reason that not so many
machines have memory hotplug hardware capability.
Which then means, IMHO, this functionality should be separate: have a
CPU hotplug callback and a memory hotplug callback.
And you kinda do that in
Subject: [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support
but then this all calls into a single handle_hotplug_event() and that
hp_action doesn't really matter.
It is used in the call to
arch_crash_handle_hotplug_event(image, hp_action);
but that hp_action argument is unused in the x86 version.
IOW, you can do this callback regardless whether it is a CPU or memory
hotplug event.
So thinking about it, a single CONFIG_CRASH_HOTPLUG which unifies those
CPU and memory hotplug callback functionality makes most sense to me.
Because you don't really differentiate between the two in the callback
actions.
Anyway, this is how I see it from here. I could very well be missing an
aspect, of course.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
2022-11-09 21:31 ` Borislav Petkov
@ 2022-11-09 22:12 ` Eric DeVolder
-1 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-09 22:12 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/9/22 15:31, Borislav Petkov wrote:
> On Wed, Nov 09, 2022 at 09:48:33AM -0600, Eric DeVolder wrote:
>> ...
>> which then defaults HOTPLUG_CPU to on and thus this code/ifdef in question.
>
> defconfig can sometimes lag reality. In this case, the majority of
> machines have SMP=y because the majority of machines out there are,
> well, multicore.
>
>> So at this point, I'm still not sure if you want the ifdef line:
>> - removed altogether
>> - transitioned to CRASH_HOTPLUG
>> - leave as is
>
> So let's think out loud:
>
> * the majority of machines will have CONFIG_HOTPLUG_CPU=y because
> they're SMP machines and we want the elfcorehdr updates to happen when
> CPUs get offlined or onlined.
>
> CONFIG_MEMORY_HOTPLUG is most likely going to be =n on the majority of
> machines out there.
>
> (Note how the deciding factor for all this is what would make sense on
> the prevailing majority of machines out there.)
>
> And memory hotplug will be off for the simple reason that not so many
> machines have memory hotplug hardware capability.
>
> Which then means, IMHO, this functionality should be separate: have a
> CPU hotplug callback and a memory hotplug callback.
>
> And you kinda do that in
>
> Subject: [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support
>
> but then this all calls into a single handle_hotplug_event() and that
> hp_action doesn't really matter.
>
> It is used in the call to
>
> arch_crash_handle_hotplug_event(image, hp_action);
>
> but that hp_action argument is unused in the x86 version. >
> IOW, you can do this callback regardless whether it is a CPU or memory
> hotplug event.
>
> So thinking about it, a single CONFIG_CRASH_HOTPLUG which unifies those
> CPU and memory hotplug callback functionality makes most sense to me.
> Because you don't really differentiate between the two in the callback
> actions.
>
> Anyway, this is how I see it from here. I could very well be missing an
> aspect, of course.
>
> Thx.
>
OK, I'll put in CRASH_HOTPLUG! Expect v14 soon!
Thank you!
eric
^ permalink raw reply [flat|nested] 40+ messages in thread
* Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support
@ 2022-11-09 22:12 ` Eric DeVolder
0 siblings, 0 replies; 40+ messages in thread
From: Eric DeVolder @ 2022-11-09 22:12 UTC (permalink / raw)
To: Borislav Petkov
Cc: linux-kernel, x86, kexec, ebiederm, dyoung, bhe, vgoyal, tglx,
mingo, dave.hansen, hpa, nramas, thomas.lendacky, robh, efault,
rppt, david, sourabhjain, konrad.wilk, boris.ostrovsky
On 11/9/22 15:31, Borislav Petkov wrote:
> On Wed, Nov 09, 2022 at 09:48:33AM -0600, Eric DeVolder wrote:
>> ...
>> which then defaults HOTPLUG_CPU to on and thus this code/ifdef in question.
>
> defconfig can sometimes lag reality. In this case, the majority of
> machines have SMP=y because the majority of machines out there are,
> well, multicore.
>
>> So at this point, I'm still not sure if you want the ifdef line:
>> - removed altogether
>> - transitioned to CRASH_HOTPLUG
>> - leave as is
>
> So let's think out loud:
>
> * the majority of machines will have CONFIG_HOTPLUG_CPU=y because
> they're SMP machines and we want the elfcorehdr updates to happen when
> CPUs get offlined or onlined.
>
> CONFIG_MEMORY_HOTPLUG is most likely going to be =n on the majority of
> machines out there.
>
> (Note how the deciding factor for all this is what would make sense on
> the prevailing majority of machines out there.)
>
> And memory hotplug will be off for the simple reason that not so many
> machines have memory hotplug hardware capability.
>
> Which then means, IMHO, this functionality should be separate: have a
> CPU hotplug callback and a memory hotplug callback.
>
> And you kinda do that in
>
> Subject: [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support
>
> but then this all calls into a single handle_hotplug_event() and that
> hp_action doesn't really matter.
>
> It is used in the call to
>
> arch_crash_handle_hotplug_event(image, hp_action);
>
> but that hp_action argument is unused in the x86 version. >
> IOW, you can do this callback regardless whether it is a CPU or memory
> hotplug event.
>
> So thinking about it, a single CONFIG_CRASH_HOTPLUG which unifies those
> CPU and memory hotplug callback functionality makes most sense to me.
> Because you don't really differentiate between the two in the callback
> actions.
>
> Anyway, this is how I see it from here. I could very well be missing an
> aspect, of course.
>
> Thx.
>
OK, I'll put in CRASH_HOTPLUG! Expect v14 soon!
Thank you!
eric
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
^ permalink raw reply [flat|nested] 40+ messages in thread
end of thread, other threads:[~2022-11-09 22:13 UTC | newest]
Thread overview: 40+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-10-31 19:35 [PATCH v13 0/7] crash: Kernel handling of CPU and memory hot un/plug Eric DeVolder
2022-10-31 19:35 ` Eric DeVolder
2022-10-31 19:35 ` [PATCH v13 1/7] crash: move crash_prepare_elf64_headers() Eric DeVolder
2022-10-31 19:35 ` Eric DeVolder
2022-10-31 19:35 ` [PATCH v13 2/7] crash: prototype change for crash_prepare_elf64_headers() Eric DeVolder
2022-10-31 19:35 ` Eric DeVolder
2022-10-31 19:36 ` [PATCH v13 3/7] crash: add generic infrastructure for crash hotplug support Eric DeVolder
2022-10-31 19:36 ` Eric DeVolder
2022-10-31 19:36 ` [PATCH v13 4/7] kexec: exclude elfcorehdr from the segment digest Eric DeVolder
2022-10-31 19:36 ` Eric DeVolder
2022-10-31 19:36 ` [PATCH v13 5/7] kexec: exclude hot remove cpu from elfcorehdr notes Eric DeVolder
2022-10-31 19:36 ` Eric DeVolder
2022-10-31 19:36 ` [PATCH v13 6/7] crash: memory and cpu hotplug sysfs attributes Eric DeVolder
2022-10-31 19:36 ` Eric DeVolder
2022-10-31 19:36 ` [PATCH v13 7/7] x86/crash: add x86 crash hotplug support Eric DeVolder
2022-10-31 19:36 ` Eric DeVolder
2022-10-31 21:04 ` Borislav Petkov
2022-10-31 21:04 ` Borislav Petkov
2022-11-01 15:45 ` Eric DeVolder
2022-11-01 15:45 ` Eric DeVolder
2022-11-02 9:26 ` Borislav Petkov
2022-11-02 9:26 ` Borislav Petkov
2022-11-02 14:55 ` Eric DeVolder
2022-11-02 14:55 ` Eric DeVolder
2022-11-02 16:19 ` Borislav Petkov
2022-11-02 16:19 ` Borislav Petkov
2022-11-02 16:54 ` Eric DeVolder
2022-11-02 16:54 ` Eric DeVolder
2022-11-02 18:49 ` Borislav Petkov
2022-11-02 18:49 ` Borislav Petkov
2022-11-02 18:57 ` Eric DeVolder
2022-11-02 18:57 ` Eric DeVolder
2022-11-02 19:22 ` Borislav Petkov
2022-11-02 19:22 ` Borislav Petkov
2022-11-09 15:48 ` Eric DeVolder
2022-11-09 15:48 ` Eric DeVolder
2022-11-09 21:31 ` Borislav Petkov
2022-11-09 21:31 ` Borislav Petkov
2022-11-09 22:12 ` Eric DeVolder
2022-11-09 22:12 ` Eric DeVolder
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