linux-kernel - Re: [PATCH 3/3] KVM: x86: correct mwait and monitor emulation

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Message-ID: <53A1C1F2.4010909@redhat.com>
Date:	Wed, 18 Jun 2014 18:44:34 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Bandan Das <bsd@...hat.com>, Nadav Amit <namit@...technion.ac.il>
CC:	gleb@...nel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, joro@...tes.org
Subject: Re: [PATCH 3/3] KVM: x86: correct mwait and monitor emulation

Il 18/06/2014 18:43, Bandan Das ha scritto:
>> > mwait and monitor are currently handled as nop. Considering this behavior, they
>> > should still be handled correctly, i.e., check execution conditions and generate
>> > exceptions when required. mwait and monitor may also be executed in real-mode
> Is this necessary ? They are NOPs and kvm prints that out (correctly so) to dmesg.
> Implementing them correctly is a different thing, but adding extra checks for NOPs
> just seems like adding extra cycles.

Raising the correct exception is a good thing, though.  The guest is 
going to busy wait anyway, it doesn't matter how fast it does that. :)

Paolo
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