* [PATCH v2 0/2] x86/setup: consolidate early memory reservations
@ 2021-01-28 10:57 Mike Rapoport
2021-01-28 10:57 ` [PATCH v2 1/2] " Mike Rapoport
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Mike Rapoport @ 2021-01-28 10:57 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrea Arcangeli, Baoquan He, Borislav Petkov, David Hildenbrand,
H. Peter Anvin, Ingo Molnar, Mel Gorman, Michal Hocko,
Mike Rapoport, Mike Rapoport, Qian Cai, Thomas Gleixner,
Vlastimil Babka, linux-kernel, linux-mm, x86
From: Mike Rapoport <rppt@linux.ibm.com>
Hi,
David noticed that we do some of memblock_reserve() calls after allocations
are possible:
https://lore.kernel.org/lkml/6ba6bde3-1520-5cd0-f987-32d543f0b79f@redhat.com
For now there is no actual problem because in top-down mode we allocate
from the end of the memory and in bottom-up mode we allocate above the
kernel image. But there is a patch in the mm tree that allow bottom-up
allocations below the kernel:
https://lore.kernel.org/lkml/20201217201214.3414100-2-guro@fb.com
and with this change we may get a memory corruption if an allocation steps
on some of the firmware areas that are yet to be reserved.
The below patches consolidate early memory reservations done during
setup_arch() so that memory used by firmware, bootloader, kernel text/data
and the memory that should be excluded from the available memory for
whatever other reason is reserved before memblock allocations are possible.
The patches are vs v5.11-rc3-mmots-2021-01-12-02-00 as I think they are
prerequisite for the memblock bottom-up changes, but if needed I can rebase
then on another tree.
v2:
* get rid of trim_platform_memory_ranges() and call trim_snb_memory()
directly, per Boris comments
* massage changelog and comments to use passive voice, per Boris
* add Acked-by and Reviewed-by, thanks Boris and David
v1: https://lore.kernel.org/lkml/20210115083255.12744-1-rppt@kernel.org
Mike Rapoport (2):
x86/setup: consolidate early memory reservations
x86/setup: merge several reservations of start of the memory
arch/x86/kernel/setup.c | 96 ++++++++++++++++++-----------------------
1 file changed, 42 insertions(+), 54 deletions(-)
--
2.28.0
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2 1/2] x86/setup: consolidate early memory reservations
2021-01-28 10:57 [PATCH v2 0/2] x86/setup: consolidate early memory reservations Mike Rapoport
@ 2021-01-28 10:57 ` Mike Rapoport
2021-01-28 10:57 ` [PATCH v2 2/2] x86/setup: merge several reservations of start of the memory Mike Rapoport
2021-02-05 19:47 ` [PATCH v2 0/2] x86/setup: consolidate early memory reservations Mike Rapoport
2 siblings, 0 replies; 4+ messages in thread
From: Mike Rapoport @ 2021-01-28 10:57 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrea Arcangeli, Baoquan He, Borislav Petkov, David Hildenbrand,
H. Peter Anvin, Ingo Molnar, Mel Gorman, Michal Hocko,
Mike Rapoport, Mike Rapoport, Qian Cai, Thomas Gleixner,
Vlastimil Babka, linux-kernel, linux-mm, x86, Borislav Petkov
From: Mike Rapoport <rppt@linux.ibm.com>
The early reservations of memory areas used by the firmware, bootloader,
kernel text and data are spread over setup_arch(). Moreover, some of them
happen *after* memblock allocations, e.g trim_platform_memory_ranges() and
trim_low_memory_range() are called after reserve_real_mode() that allocates
memory.
There was no corruption of these memory regions because memblock always
allocates memory either from the end of memory (in top-down mode) or above
the kernel image (in bottom-up mode). However, the bottom up mode is going
to be updated to span the entire memory [1] to avoid limitations caused by
KASLR.
Consolidate early memory reservations in a dedicated function to improve
robustness against future changes. Having the early reservations in one
place also makes it clearer what memory must be reserved before we allow
memblock allocations.
[1] https://lore.kernel.org/lkml/20201217201214.3414100-2-guro@fb.com
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/setup.c | 92 ++++++++++++++++++++---------------------
1 file changed, 44 insertions(+), 48 deletions(-)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 3412c4595efd..3b582406363a 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -646,18 +646,6 @@ static void __init trim_snb_memory(void)
}
}
-/*
- * Here we put platform-specific memory range workarounds, i.e.
- * memory known to be corrupt or otherwise in need to be reserved on
- * specific platforms.
- *
- * If this gets used more widely it could use a real dispatch mechanism.
- */
-static void __init trim_platform_memory_ranges(void)
-{
- trim_snb_memory();
-}
-
static void __init trim_bios_range(void)
{
/*
@@ -728,7 +716,38 @@ static void __init trim_low_memory_range(void)
*/
memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));
}
-
+
+static void __init early_reserve_memory(void)
+{
+ /*
+ * Reserve the memory occupied by the kernel between _text and
+ * __end_of_kernel_reserve symbols. Any kernel sections after the
+ * __end_of_kernel_reserve symbol must be explicitly reserved with a
+ * separate memblock_reserve() or they will be discarded.
+ */
+ memblock_reserve(__pa_symbol(_text),
+ (unsigned long)__end_of_kernel_reserve - (unsigned long)_text);
+
+ /*
+ * Make sure page 0 is always reserved because on systems with
+ * L1TF its contents can be leaked to user processes.
+ */
+ memblock_reserve(0, PAGE_SIZE);
+
+ early_reserve_initrd();
+
+ if (efi_enabled(EFI_BOOT))
+ efi_memblock_x86_reserve_range();
+
+ memblock_x86_reserve_range_setup_data();
+
+ reserve_ibft_region();
+ reserve_bios_regions();
+
+ trim_snb_memory();
+ trim_low_memory_range();
+}
+
/*
* Dump out kernel offset information on panic.
*/
@@ -763,29 +782,6 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
void __init setup_arch(char **cmdline_p)
{
- /*
- * Reserve the memory occupied by the kernel between _text and
- * __end_of_kernel_reserve symbols. Any kernel sections after the
- * __end_of_kernel_reserve symbol must be explicitly reserved with a
- * separate memblock_reserve() or they will be discarded.
- */
- memblock_reserve(__pa_symbol(_text),
- (unsigned long)__end_of_kernel_reserve - (unsigned long)_text);
-
- /*
- * Make sure page 0 is always reserved because on systems with
- * L1TF its contents can be leaked to user processes.
- */
- memblock_reserve(0, PAGE_SIZE);
-
- early_reserve_initrd();
-
- /*
- * At this point everything still needed from the boot loader
- * or BIOS or kernel text should be early reserved or marked not
- * RAM in e820. All other memory is free game.
- */
-
#ifdef CONFIG_X86_32
memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
@@ -909,8 +905,18 @@ void __init setup_arch(char **cmdline_p)
parse_early_param();
- if (efi_enabled(EFI_BOOT))
- efi_memblock_x86_reserve_range();
+ /*
+ * Do some memory reservations *before* memory is added to
+ * memblock, so memblock allocations won't overwrite it.
+ * Do it after early param, so we could get (unlikely) panic from
+ * serial.
+ *
+ * After this point everything still needed from the boot loader or
+ * firmware or kernel text should be early reserved or marked not
+ * RAM in e820. All other memory is free game.
+ */
+ early_reserve_memory();
+
#ifdef CONFIG_MEMORY_HOTPLUG
/*
* Memory used by the kernel cannot be hot-removed because Linux
@@ -937,9 +943,6 @@ void __init setup_arch(char **cmdline_p)
x86_report_nx();
- /* after early param, so could get panic from serial */
- memblock_x86_reserve_range_setup_data();
-
if (acpi_mps_check()) {
#ifdef CONFIG_X86_LOCAL_APIC
disable_apic = 1;
@@ -1031,8 +1034,6 @@ void __init setup_arch(char **cmdline_p)
*/
find_smp_config();
- reserve_ibft_region();
-
early_alloc_pgt_buf();
/*
@@ -1053,8 +1054,6 @@ void __init setup_arch(char **cmdline_p)
*/
sev_setup_arch();
- reserve_bios_regions();
-
efi_fake_memmap();
efi_find_mirror();
efi_esrt_init();
@@ -1080,9 +1079,6 @@ void __init setup_arch(char **cmdline_p)
reserve_real_mode();
- trim_platform_memory_ranges();
- trim_low_memory_range();
-
init_mem_mapping();
idt_setup_early_pf();
--
2.28.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2 2/2] x86/setup: merge several reservations of start of the memory
2021-01-28 10:57 [PATCH v2 0/2] x86/setup: consolidate early memory reservations Mike Rapoport
2021-01-28 10:57 ` [PATCH v2 1/2] " Mike Rapoport
@ 2021-01-28 10:57 ` Mike Rapoport
2021-02-05 19:47 ` [PATCH v2 0/2] x86/setup: consolidate early memory reservations Mike Rapoport
2 siblings, 0 replies; 4+ messages in thread
From: Mike Rapoport @ 2021-01-28 10:57 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrea Arcangeli, Baoquan He, Borislav Petkov, David Hildenbrand,
H. Peter Anvin, Ingo Molnar, Mel Gorman, Michal Hocko,
Mike Rapoport, Mike Rapoport, Qian Cai, Thomas Gleixner,
Vlastimil Babka, linux-kernel, linux-mm, x86, Borislav Petkov
From: Mike Rapoport <rppt@linux.ibm.com>
Currently the first several pages are reserved both to avoid leaking their
contents on systems with L1TF and to avoid corrupting BIOS memory.
Merge the two memory reservations.
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/setup.c | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 3b582406363a..b36624e3dc9e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -703,20 +703,6 @@ static int __init parse_reservelow(char *p)
early_param("reservelow", parse_reservelow);
-static void __init trim_low_memory_range(void)
-{
- /*
- * A special case is the first 4Kb of memory;
- * This is a BIOS owned area, not kernel ram, but generally
- * not listed as such in the E820 table.
- *
- * This typically reserves additional memory (64KiB by default)
- * since some BIOSes are known to corrupt low memory. See the
- * Kconfig help text for X86_RESERVE_LOW.
- */
- memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));
-}
-
static void __init early_reserve_memory(void)
{
/*
@@ -729,10 +715,17 @@ static void __init early_reserve_memory(void)
(unsigned long)__end_of_kernel_reserve - (unsigned long)_text);
/*
- * Make sure page 0 is always reserved because on systems with
- * L1TF its contents can be leaked to user processes.
+ * The first 4Kb of memory is a BIOS owned area, but generally it is
+ * not listed as such in the E820 table.
+ *
+ * Reserve the first memory page and typically some additional
+ * memory (64KiB by default) since some BIOSes are known to corrupt
+ * low memory. See the Kconfig help text for X86_RESERVE_LOW.
+ *
+ * In addition, make sure page 0 is always reserved because on
+ * systems with L1TF its contents can be leaked to user processes.
*/
- memblock_reserve(0, PAGE_SIZE);
+ memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));
early_reserve_initrd();
@@ -745,7 +738,6 @@ static void __init early_reserve_memory(void)
reserve_bios_regions();
trim_snb_memory();
- trim_low_memory_range();
}
/*
--
2.28.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2 0/2] x86/setup: consolidate early memory reservations
2021-01-28 10:57 [PATCH v2 0/2] x86/setup: consolidate early memory reservations Mike Rapoport
2021-01-28 10:57 ` [PATCH v2 1/2] " Mike Rapoport
2021-01-28 10:57 ` [PATCH v2 2/2] x86/setup: merge several reservations of start of the memory Mike Rapoport
@ 2021-02-05 19:47 ` Mike Rapoport
2 siblings, 0 replies; 4+ messages in thread
From: Mike Rapoport @ 2021-02-05 19:47 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrea Arcangeli, Baoquan He, Borislav Petkov, David Hildenbrand,
H. Peter Anvin, Ingo Molnar, Mel Gorman, Michal Hocko,
Mike Rapoport, Qian Cai, Thomas Gleixner, Vlastimil Babka,
linux-kernel, linux-mm, x86
Hi,
Any comments on this?
On Thu, Jan 28, 2021 at 12:57:09PM +0200, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
>
> Hi,
>
> David noticed that we do some of memblock_reserve() calls after allocations
> are possible:
>
> https://lore.kernel.org/lkml/6ba6bde3-1520-5cd0-f987-32d543f0b79f@redhat.com
>
> For now there is no actual problem because in top-down mode we allocate
> from the end of the memory and in bottom-up mode we allocate above the
> kernel image. But there is a patch in the mm tree that allow bottom-up
> allocations below the kernel:
>
> https://lore.kernel.org/lkml/20201217201214.3414100-2-guro@fb.com
>
> and with this change we may get a memory corruption if an allocation steps
> on some of the firmware areas that are yet to be reserved.
>
> The below patches consolidate early memory reservations done during
> setup_arch() so that memory used by firmware, bootloader, kernel text/data
> and the memory that should be excluded from the available memory for
> whatever other reason is reserved before memblock allocations are possible.
>
> The patches are vs v5.11-rc3-mmots-2021-01-12-02-00 as I think they are
> prerequisite for the memblock bottom-up changes, but if needed I can rebase
> then on another tree.
>
> v2:
> * get rid of trim_platform_memory_ranges() and call trim_snb_memory()
> directly, per Boris comments
> * massage changelog and comments to use passive voice, per Boris
> * add Acked-by and Reviewed-by, thanks Boris and David
>
> v1: https://lore.kernel.org/lkml/20210115083255.12744-1-rppt@kernel.org
>
> Mike Rapoport (2):
> x86/setup: consolidate early memory reservations
> x86/setup: merge several reservations of start of the memory
>
> arch/x86/kernel/setup.c | 96 ++++++++++++++++++-----------------------
> 1 file changed, 42 insertions(+), 54 deletions(-)
>
> --
> 2.28.0
>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 4+ messages in thread
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