linux-kernel - Re: [PATCH 01/12][RFC v3] x86, hibernate: Fix nosave

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Date:   Fri, 21 Sep 2018 00:05:02 +0200
From:   Pavel Machek <pavel@....cz>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Len Brown <len.brown@...el.com>,
        Zhimin Gu <kookoo.gu@...el.com>
Subject: Re: [PATCH 01/12][RFC v3] x86, hibernate: Fix nosave_regions setup
 for hibernation

On Wed 2018-09-19 15:37:15, Chen Yu wrote:
> From: Zhimin Gu <kookoo.gu@...el.com>
> 
> 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:
> 
> 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@....cz>

Thanks.

I think this is nasty enough to add Cc: stable.
									Pavel
-- 
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