linux-kernel - Re: [PATCH -v2] x86/boot/compressed: Register dummy NMI handler in EFI boot loader, to avoid kdump crashes

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Message-ID: <4b3d00ff-fcda-e184-7121-9cd65ed1a602@huawei.com>
Date:   Thu, 12 Jan 2023 10:07:19 +0800
From:   Zeng Heng <zengheng4@...wei.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Ingo Molnar <mingo@...nel.org>, <michael.roth@....com>,
        <hpa@...or.com>, <tglx@...utronix.de>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <kirill.shutemov@...ux.intel.com>, <jroedel@...e.de>,
        <keescook@...omium.org>, <mingo@...hat.com>,
        <dave.hansen@...ux.intel.com>, <brijesh.singh@....com>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <liwei391@...wei.com>, <xiexiuqi@...wei.com>
Subject: Re: [PATCH -v2] x86/boot/compressed: Register dummy NMI handler in
 EFI boot loader, to avoid kdump crashes


On 2023/1/11 0:09, Borislav Petkov wrote:
> On Tue, Jan 10, 2023 at 01:57:05PM +0100, Borislav Petkov wrote:
>> I'm doubtful now as you're injecting errors so you're not really in #MC context
>> but in this contrived context which is actually an NMI one. So we need to think
>> about how to fix this case.
> I did some more thinking:
>
> *if* this really is a real issue - and not some silly qemu games - then
> native_machine_crash_shutdown() does all the cleanup before the kdump kernel is
> started.
>
> Any NMI clearing, maybe using iret_to_self() etc, #MC resetting etc should
> happen there and not anywhere else.

You mean native_machine_crash_shutdown() should cleanup the NMI 
interrupt status

before enter kexec?


But how about the watchdog raise NMI interrupt after 
native_machine_crash_shutdown()

or mce_wrmsrl(MSR_IA32_MCG_STATUS, 0) or any else cleanup function?


B.R.,

Zeng Heng