Message-ID: <53A1C1F2.4010909@redhat.com>
Date: Wed, 18 Jun 2014 18:44:34 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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To: Bandan Das <bsd@redhat.com>, Nadav Amit <namit@cs.technion.ac.il>
CC: gleb@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
        x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        joro@8bytes.org
Subject: Re: [PATCH 3/3] KVM: x86: correct mwait and monitor emulation
References: <1403101176-23664-1-git-send-email-namit@cs.technion.ac.il>	<1403101176-23664-4-git-send-email-namit@cs.technion.ac.il> <jpg7g4ew4m6.fsf@redhat.com>
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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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