linux-kernel - Re: [PATCH] kvm: fix cpuid eax

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Message-ID: <4F9FDCC4.3030302@redhat.com>
Date:	Tue, 01 May 2012 15:53:24 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Anthony Liguori <anthony@...emonkey.ws>
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, davej@...hat.com
Subject: Re: [PATCH] kvm: fix cpuid eax

On 04/30/2012 11:37 PM, Anthony Liguori wrote:
> On 04/30/2012 09:39 AM, Michael S. Tsirkin wrote:
>> cpuid eax should return the max leaf so that
>> guests can find out the valid range.
>> This matches Xen et al.
>
> What KVM does here predates Xen and Hyper-V.
>
> This is an ABI breaker.

First, I don't think we ever documented eax, so nothing can rely on it.
Second, this isn't guest visible, it's just part of
KVM_GET_SUPPORTED_CPUID (used by qemu's -cpu host, but doesn't affect
qemu stable cpus).

-- 
error compiling committee.c: too many arguments to function

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