Re: KVM causes #GP on XRSTORS

From: Nadav Amit
Date: Thu Nov 20 2014 - 20:09:45 EST

> On Nov 21, 2014, at 02:10, Wanpeng Li <> 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 donât 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.


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