Messages in this thread | | | Subject | Re: [PATCH 1/1] KVM: don't allow irq_fpu_usable when the VCPU's XCR0 is loaded | From | Xiao Guangrong <> | Date | Wed, 16 Mar 2016 11:55:05 +0800 |
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On 03/16/2016 03:32 AM, Paolo Bonzini wrote: > > > On 15/03/2016 19:27, Andy Lutomirski wrote: >> On Mon, Mar 14, 2016 at 6:17 AM, Paolo Bonzini <pbonzini@redhat.com> wrote: >>> >>> >>> On 11/03/2016 22:33, David Matlack wrote: >>>>> Is this better than just always keeping the host's XCR0 loaded outside >>>>> if the KVM interrupts-disabled region? >>>> >>>> Probably not. AFAICT KVM does not rely on it being loaded outside that >>>> region. xsetbv isn't insanely expensive, is it? Maybe to minimize the >>>> time spent with interrupts disabled it was put outside. >>>> >>>> I do like that your solution would be contained to KVM. >>> >>> I agree with Andy. We do want a fix for recent kernels because of the >>> !eager_fpu case that Guangrong mentioned.
Relying on interrupt is not easy as XCR0 can not be automatically saved/loaded by VMCS... Once interrupt happens, it will use guest's XCR0 anyway.
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