* KVM causes #GP on XRSTORS
@ 2014-11-20 16:34 Nadav Amit
2014-11-20 22:18 ` Yu, Fenghua
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Nadav Amit @ 2014-11-20 16:34 UTC (permalink / raw)
To: Paolo Bonzini, fenghua.yu; +Cc: kvm list
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?
Thanks,
Nadav
^ permalink raw reply [flat|nested] 8+ messages in thread
* RE: KVM causes #GP on XRSTORS
2014-11-20 16:34 KVM causes #GP on XRSTORS Nadav Amit
@ 2014-11-20 22:18 ` Yu, Fenghua
2014-11-21 0:10 ` Wanpeng Li
2014-11-21 14:46 ` Paolo Bonzini
2 siblings, 0 replies; 8+ messages in thread
From: Yu, Fenghua @ 2014-11-20 22:18 UTC (permalink / raw)
To: Nadav Amit, Paolo Bonzini; +Cc: kvm list
> From: Nadav Amit [mailto:nadav.amit@gmail.com]
> Sent: Thursday, November 20, 2014 8:34 AM
> To: Paolo Bonzini; Yu, Fenghua
> Cc: kvm list
> Subject: KVM causes #GP on XRSTORS
>
> 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?
In dmesg, do you see "xsave: ......... using compacted form"?
If you use kernel "noxsaves", does KVM work fine?
Thanks.
-Fenghua
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: KVM causes #GP on XRSTORS
2014-11-20 16:34 KVM causes #GP on XRSTORS Nadav Amit
2014-11-20 22:18 ` Yu, Fenghua
@ 2014-11-21 0:10 ` Wanpeng Li
2014-11-21 1:09 ` Nadav Amit
2014-11-21 14:46 ` Paolo Bonzini
2 siblings, 1 reply; 8+ messages in thread
From: Wanpeng Li @ 2014-11-21 0:10 UTC (permalink / raw)
To: Nadav Amit; +Cc: Paolo Bonzini, fenghua.yu, kvm list, linux-kernel
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.
Regards,
Wanpeng Li
>
>Thanks,
>Nadav
>
>--
>To unsubscribe from this list: send the line "unsubscribe kvm" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: KVM causes #GP on XRSTORS
2014-11-21 0:10 ` Wanpeng Li
@ 2014-11-21 1:09 ` Nadav Amit
0 siblings, 0 replies; 8+ messages in thread
From: Nadav Amit @ 2014-11-21 1:09 UTC (permalink / raw)
To: Wanpeng Li; +Cc: Paolo Bonzini, fenghua.yu, kvm list, linux-kernel
> On Nov 21, 2014, at 02:10, Wanpeng Li <wanpeng.li@linux.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
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: KVM causes #GP on XRSTORS
2014-11-20 16:34 KVM causes #GP on XRSTORS Nadav Amit
2014-11-20 22:18 ` Yu, Fenghua
2014-11-21 0:10 ` Wanpeng Li
@ 2014-11-21 14:46 ` Paolo Bonzini
2014-11-21 18:34 ` Paolo Bonzini
` (2 more replies)
2 siblings, 3 replies; 8+ messages in thread
From: Paolo Bonzini @ 2014-11-21 14:46 UTC (permalink / raw)
To: Nadav Amit, fenghua.yu; +Cc: kvm list, Eduardo Habkost
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
a patch later today or next week (CCing Eduardo for this).
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
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: KVM causes #GP on XRSTORS
2014-11-21 14:46 ` Paolo Bonzini
@ 2014-11-21 18:34 ` Paolo Bonzini
2014-11-24 2:05 ` Wanpeng Li
2014-11-25 18:41 ` Eduardo Habkost
2 siblings, 0 replies; 8+ messages in thread
From: Paolo Bonzini @ 2014-11-21 18:34 UTC (permalink / raw)
To: kvm; +Cc: kvm list, Eduardo Habkost
On 21/11/2014 15:46, Paolo Bonzini wrote:
> 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
> a patch later today or next week (CCing Eduardo for this).
Actually no change in QEMU is needed to hide XSAVES; the KVM patch I
just sent should be enough for "-cpu host" to work.
We still need the information on processor support though, in order to
enable the feature with the right -cpu options. I assume Nadav was
using "-cpu host".
Paolo
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: KVM causes #GP on XRSTORS
2014-11-21 14:46 ` Paolo Bonzini
2014-11-21 18:34 ` Paolo Bonzini
@ 2014-11-24 2:05 ` Wanpeng Li
2014-11-25 18:41 ` Eduardo Habkost
2 siblings, 0 replies; 8+ messages in thread
From: Wanpeng Li @ 2014-11-24 2:05 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Nadav Amit, fenghua.yu, kvm list, Eduardo Habkost, linux-kernel
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
>--
>To unsubscribe from this list: send the line "unsubscribe kvm" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: KVM causes #GP on XRSTORS
2014-11-21 14:46 ` Paolo Bonzini
2014-11-21 18:34 ` Paolo Bonzini
2014-11-24 2:05 ` Wanpeng Li
@ 2014-11-25 18:41 ` Eduardo Habkost
2 siblings, 0 replies; 8+ messages in thread
From: Eduardo Habkost @ 2014-11-25 18:41 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Nadav Amit, fenghua.yu, kvm list
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
> a patch later today or next week (CCing Eduardo for this).
>
> 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.
Oh, now I see that KVM uses xsave_state(), which uses XSAVEOPT and
XSAVES depending on the host CPU features. I didn't know that.
QEMU already expects the standard format to be part of the KVM_GET_XSAVE
ABI. So this would already cause problems in host CPUs supporting
XSAVES, even if XSAVES is not exposed to guests yet.
--
Eduardo
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2014-11-25 18:41 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-11-20 16:34 KVM causes #GP on XRSTORS Nadav Amit
2014-11-20 22:18 ` Yu, Fenghua
2014-11-21 0:10 ` Wanpeng Li
2014-11-21 1:09 ` Nadav Amit
2014-11-21 14:46 ` Paolo Bonzini
2014-11-21 18:34 ` Paolo Bonzini
2014-11-24 2:05 ` Wanpeng Li
2014-11-25 18:41 ` Eduardo Habkost
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