From: Chao Peng <chao.p.peng@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org,
Eduardo Habkost <ehabkost@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Richard Henderson <rth@twiddle.net>
Subject: Re: [PATCH] target-i386: kvm: cache KVM_GET_SUPPORTED_CPUID data
Date: Tue, 14 Jun 2016 16:31:37 +0800 [thread overview]
Message-ID: <20160614083136.GD21465@pengc-linux.bj.intel.com> (raw)
In-Reply-To: <7ce88285-2d4c-7b4a-767a-7e6c9eb25f2b@redhat.com>
On Tue, Jun 14, 2016 at 10:21:41AM +0200, Paolo Bonzini wrote:
>
>
> On 14/06/2016 07:01, Chao Peng wrote:
> >> >
> >> > Which are the CPUID leaves for which KVM_GET_SUPPORTED_CPUID is not
> >> > stateless? I cannot find any.
> > I have though leaf 0xd, sub leaf 1 is not stateless, as the size of
> > xsave buffer(EBX) is based on XCR0 | IA32_XSS. But after looking KVM
> > code more carefully, seems I was wrong. The code calculates EBX with the
> > host xcr0 but not guest xcr0, nor guest IA32_XSS (not sure if this is
> > the correct behavior), so it can always returns constant data on a
> > certain machine.
>
> Indeed, KVM computes the correct value at runtime, but
> KVM_GET_SUPPORTED_CPUID runs before there is a value for guest XCR0 or
> guest IA32_XSS.
Yes, this is the point.
>
> Thanks, I've queued the patch for QEMU 2.7.
Thanks :)
Chao
WARNING: multiple messages have this Message-ID (diff)
From: Chao Peng <chao.p.peng@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org,
Eduardo Habkost <ehabkost@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH] target-i386: kvm: cache KVM_GET_SUPPORTED_CPUID data
Date: Tue, 14 Jun 2016 16:31:37 +0800 [thread overview]
Message-ID: <20160614083136.GD21465@pengc-linux.bj.intel.com> (raw)
In-Reply-To: <7ce88285-2d4c-7b4a-767a-7e6c9eb25f2b@redhat.com>
On Tue, Jun 14, 2016 at 10:21:41AM +0200, Paolo Bonzini wrote:
>
>
> On 14/06/2016 07:01, Chao Peng wrote:
> >> >
> >> > Which are the CPUID leaves for which KVM_GET_SUPPORTED_CPUID is not
> >> > stateless? I cannot find any.
> > I have though leaf 0xd, sub leaf 1 is not stateless, as the size of
> > xsave buffer(EBX) is based on XCR0 | IA32_XSS. But after looking KVM
> > code more carefully, seems I was wrong. The code calculates EBX with the
> > host xcr0 but not guest xcr0, nor guest IA32_XSS (not sure if this is
> > the correct behavior), so it can always returns constant data on a
> > certain machine.
>
> Indeed, KVM computes the correct value at runtime, but
> KVM_GET_SUPPORTED_CPUID runs before there is a value for guest XCR0 or
> guest IA32_XSS.
Yes, this is the point.
>
> Thanks, I've queued the patch for QEMU 2.7.
Thanks :)
Chao
next prev parent reply other threads:[~2016-06-14 8:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-13 2:21 [PATCH] target-i386: kvm: cache KVM_GET_SUPPORTED_CPUID data Chao Peng
2016-06-13 2:21 ` [Qemu-devel] " Chao Peng
2016-06-13 10:02 ` Paolo Bonzini
2016-06-13 10:02 ` [Qemu-devel] " Paolo Bonzini
2016-06-14 5:01 ` Chao Peng
2016-06-14 5:01 ` [Qemu-devel] " Chao Peng
2016-06-14 8:21 ` Paolo Bonzini
2016-06-14 8:21 ` [Qemu-devel] " Paolo Bonzini
2016-06-14 8:31 ` Chao Peng [this message]
2016-06-14 8:31 ` Chao Peng
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