linux-kernel - Re: [PATCH v4 0/4] x86/crash: Fix double NMI shootdown bug

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Date:   Sat, 28 Jan 2023 11:52:39 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Tom Lendacky <thomas.lendacky@....com>, stable@...r.kernel
Subject: Re: [PATCH v4 0/4] x86/crash: Fix double NMI shootdown bug

On 27/01/2023 21:05, Sean Christopherson wrote:
> On Wed, 30 Nov 2022 23:36:46 +0000, Sean Christopherson wrote:
>> Fix a double NMI shootdown bug found and debugged by Guilherme, who did all
>> the hard work.  NMI shootdown is a one-time thing; the handler leaves NMIs
>> blocked and enters halt.  At best, a second (or third...) shootdown is an
>> expensive nop, at worst it can hang the kernel and prevent kexec'ing into
>> a new kernel, e.g. prior to the hardening of register_nmi_handler(), a
>> double shootdown resulted in a double list_add(), which is fatal when running
>> with CONFIG_BUG_ON_DATA_CORRUPTION=y.
>>
>> [...]
> 
> Applied to kvm-x86 misc, thanks!
> 
> [1/4] x86/crash: Disable virt in core NMI crash handler to avoid double shootdown
>       https://github.com/kvm-x86/linux/commit/26044aff37a5
> [2/4] x86/virt: Force GIF=1 prior to disabling SVM (for reboot flows)
>       https://github.com/kvm-x86/linux/commit/6a3236580b0b
> [3/4] x86/reboot: Disable virtualization in an emergency if SVM is supported
>       https://github.com/kvm-x86/linux/commit/d81f952aa657
> [4/4] x86/reboot: Disable SVM, not just VMX, when stopping CPUs
>       https://github.com/kvm-x86/linux/commit/a2b07fa7b933
> 
> --
> https://github.com/kvm-x86/linux/tree/next
> https://github.com/kvm-x86/linux/tree/fixes


Thanks a bunch Sean!