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

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Message-ID: <20190715132555.3tz4ciogkv3xlkta@treble>
Date:   Mon, 15 Jul 2019 08:25:55 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Paolo Bonzini <pbonzini@...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 Mon, Jul 15, 2019 at 03:05:33PM +0200, Paolo Bonzini wrote:
> 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".

Ah, makes sense now.  I was reading "if that happens" to mean the fault.

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

Yes, that's much clearer.  Assuming you meant to replace the entire
comment.  I also moved it to directly above the macro it's describing:


asmlinkage void __noreturn kvm_spurious_fault(void);

/*
 * Usually after catching the fault we just panic; during reboot
 * instead the instruction is ignored.
 */
#define ____kvm_handle_fault_on_reboot(insn, cleanup_insn)		\


-- 
Josh