Re: [PATCH 01/12][RFC v3] x86, hibernate: Fix nosave_regions setup for hibernation

[Rafael J. Wysocki]

On Wed, Sep 19, 2018 at 9:30 AM Chen Yu <yu.c.chen@xxxxxxxxx> wrote:
>
> From: Zhimin Gu <kookoo.gu@xxxxxxxxx>
>
> On 32bit systems, nosave_regions(non RAM areas) located between
> max_low_pfn and max_pfn are not excluded from hibernation snapshot
> currently, which may result in a machine check exception when
> trying to access these unsafe regions during hibernation:
>
> [  612.800453] Disabling lock debugging due to kernel taint
> [  612.805786] mce: [Hardware Error]: CPU 0: Machine Check Exception: 5 Bank 6: fe00000000801136
> [  612.814344] mce: [Hardware Error]: RIP !INEXACT! 60:<00000000d90be566> {swsusp_save+0x436/0x560}
> [  612.823167] mce: [Hardware Error]: TSC 1f5939fe276 ADDR dd000000 MISC 30e0000086
> [  612.830677] mce: [Hardware Error]: PROCESSOR 0:306c3 TIME 1529487426 SOCKET 0 APIC 0 microcode 24
> [  612.839581] mce: [Hardware Error]: Run the above through 'mcelog --ascii'
> [  612.846394] mce: [Hardware Error]: Machine check: Processor context corrupt
> [  612.853380] Kernel panic - not syncing: Fatal machine check
> [  612.858978] Kernel Offset: 0x18000000 from 0xc1000000 (relocation range: 0xc0000000-0xf7ffdfff)
>
> This is because on 32bit systems, pages above max_low_pfn are regarded
> as high memeory, and accessing unsafe pages might cause expected MCE.
> On the problematic 32bit system, there are reserved memory above low
> memory, which triggered the MCE:
>
> e820 memory mapping:
> [    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009d7ff] usable
> [    0.000000] BIOS-e820: [mem 0x000000000009d800-0x000000000009ffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
> [    0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000d160cfff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000d160d000-0x00000000d1613fff] ACPI NVS
> [    0.000000] BIOS-e820: [mem 0x00000000d1614000-0x00000000d1a44fff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000d1a45000-0x00000000d1ecffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000d1ed0000-0x00000000d7eeafff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000d7eeb000-0x00000000d7ffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000d8000000-0x00000000d875ffff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000d8760000-0x00000000d87fffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000d8800000-0x00000000d8fadfff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000d8fae000-0x00000000d8ffffff] ACPI data
> [    0.000000] BIOS-e820: [mem 0x00000000d9000000-0x00000000da71bfff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000da71c000-0x00000000da7fffff] ACPI NVS
> [    0.000000] BIOS-e820: [mem 0x00000000da800000-0x00000000dbb8bfff] usable
> [    0.000000] BIOS-e820: [mem 0x00000000dbb8c000-0x00000000dbffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000dd000000-0x00000000df1fffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000f8000000-0x00000000fbffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000fed00000-0x00000000fed03fff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
> [    0.000000] BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
> [    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000041edfffff] usable
>
> Fix this problem by changing pfn limit from max_low_pfn to max_pfn.
> This fix does not impact 64bit system because on 64bit max_low_pfn
> is the same as max_pfn.
>
> Acked-by: Pavel Machek <pavel@xxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Zhimin Gu <kookoo.gu@xxxxxxxxx>
> Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
> ---
>  arch/x86/kernel/setup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index b4866badb235..90ecc108bc8a 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1251,7 +1251,7 @@ void __init setup_arch(char **cmdline_p)
>         x86_init.hyper.guest_late_init();
>
>         e820__reserve_resources();
> -       e820__register_nosave_regions(max_low_pfn);
> +       e820__register_nosave_regions(max_pfn);
>
>         x86_init.resources.reserve_resources();
>
> --

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>