From: Gleb Natapov <gleb@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: emulate SAHF instruction
Date: Thu, 31 Oct 2013 17:47:07 +0200 [thread overview]
Message-ID: <20131031154707.GC20205@redhat.com> (raw)
In-Reply-To: <52726DE0.3060207@redhat.com>
On Thu, Oct 31, 2013 at 03:49:04PM +0100, Paolo Bonzini wrote:
> Il 31/10/2013 15:34, Gleb Natapov ha scritto:
> > I haven't checked AMD doc, but if it is documented that lahf/sahf #UDs at 64
> > bit we should emulate it correctly.
>
> It says "The LAHF instruction can only be executed in 64-bit mode if
> supported by the processor implementation. Check the status of ECX bit 0
> returned by CPUID function 8000_0001h to verify that the processor
> supports LAHF in 64-bit mode". Same as Intel---in fact 80000001h is an
> "AMD leaf" so to speak.
>
> I found "AMD introduced support for the instructions with their Athlon
> 64, Opteron and Turion 64 revision D processors in March 2005 and Intel
> introduced support for the instructions with the Pentium 4 G1 stepping
> in December 2005". I think we can for all practical purposes ignore the
> lahf_lm CPUID flag.
>
Yep,
Reviewed-by: Gleb Natapov <gleb@redhat.com>
--
Gleb.
prev parent reply other threads:[~2013-10-31 15:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-31 10:29 [PATCH] KVM: x86: emulate SAHF instruction Paolo Bonzini
2013-10-31 14:21 ` Gleb Natapov
2013-10-31 14:27 ` Paolo Bonzini
2013-10-31 14:34 ` Gleb Natapov
2013-10-31 14:49 ` Paolo Bonzini
2013-10-31 15:14 ` Borislav Petkov
2013-10-31 15:47 ` Gleb Natapov [this message]
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