linux-kernel - Re: KVM causes #GP on XRSTORS

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Date:	Mon, 24 Nov 2014 10:05:53 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Nadav Amit <nadav.amit@...il.com>, fenghua.yu@...el.com,
	kvm list <kvm@...r.kernel.org>,
	Eduardo Habkost <ehabkost@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: KVM causes #GP on XRSTORS

Hi Paolo,
On Fri, Nov 21, 2014 at 03:46:55PM +0100, Paolo Bonzini wrote:
>
>
>On 20/11/2014 17:34, Nadav Amit wrote:
>> Fenghua,
>> 
>> I got KVM (v3.17) crashing on a machine that supports XRSTORS - It appears to get a #GP when it is trying to load the guest FPU.
>> One reason for the #GP is that XCOMP_BV[63] is zeroed on the guest_fpu, but I am not sure it is the only problem.
>> Was KVM ever tested with XRSTORS?
>
>What is the content of the CPUID[EAX=13,ECX=0] and CPUID[EAX=13,ECX=1]
>leaves on the host?
>
>Fenghua, which processors have XSAVEC, which have XGETBV with ECX=1, and
>which have XSAVES?  We need to expose this in QEMU, for which I can send

Skylake-client supports XSAVES.

>a patch later today or next week (CCing Eduardo for this).

Actually I do the xsaves work in kvm/qemu recently and the patches are
complete, I will start to test it before send out.

Regards,
Wanpeng Li 

>
>We will also have to uncompact the XSAVE area either in KVM_GET_XSAVE or
>in QEMU.  It's probably not hard to do it in the kernel.
>
>Paolo
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