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

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Message-Id: <AC569D54-4EA9-4090-AE7E-816576BCF2B8@gmail.com>
Date:	Fri, 21 Nov 2014 03:09:36 +0200
From:	Nadav Amit <nadav.amit@...il.com>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>, fenghua.yu@...el.com,
	kvm list <kvm@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: KVM causes #GP on XRSTORS


> On Nov 21, 2014, at 02:10, Wanpeng Li <wanpeng.li@...ux.intel.com> wrote:
> 
> Hi Nadav,
> On Thu, Nov 20, 2014 at 06:34:04PM +0200, 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?
> 
> Current kvm and qemu use standard format and xsaves/xrstors should use
> compact format, in addition, vmx is still not enabled for xsaves/xrstors 
> in kvm.

Sorry, but I don’t quite understand. Should KVM work on a machine that supports xsaves/xrstors?
I am not referring to whether KVM exposes the capability to the guest, but to whether KVM should work at all.

Thanks,
Nadav


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