linux-kernel - Re: [PATCH 04/22] x86/kvm: Don't call kvm_spurious

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Message-ID: <29d30d81-bcbe-5261-b34d-12bd62df9116@redhat.com>
Date:   Mon, 15 Jul 2019 15:05:33 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 04/22] x86/kvm: Don't call kvm_spurious_fault() from
 .fixup

On 15/07/19 14:40, Josh Poimboeuf wrote:
>>>   * Hardware virtualization extension instructions may fault if a
>>>   * reboot turns off virtualization while processes are running.
>>> - * Trap the fault and ignore the instruction if that happens.
>>> + * If that happens, trap the fault and panic (unless we're rebooting).
>> Not sure the comment is better than before, but apar from that
> The previous comment didn't seem to match the code, since we only ignore
> the instruction if we're rebooting.
> 

"If that happens" refers to "a reboot turns off virtualization while
processes are running".  Perhaps

 * Usually after catching the fault we just panic; during reboot
 * instead the instruction is ignored.

Paolo