Messages in this thread Patch in this message | | | Subject | Re: [PATCH 1/2] KVM: x86: disable MPX if host did not enable MPX XSAVE features | From | Yang Zhang <> | Date | Wed, 13 Apr 2016 17:47:37 +0800 |
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On 2016/3/24 21:07, Paolo Bonzini wrote: > > > On 24/03/2016 14:06, Yang Zhang wrote: >> >> I mean why not keep the old way that only activate the eager_fpu while >> guest sees the MPX bit in CPUID, like: >> >> vcpu->arch.eager_fpu = use_eager_fpu() && guest_cpuid_has_mpx(vcpu); > > If the host uses eager FPU you can assume that it's faster than lazy FPU. > > Paolo > >> Besides, vmx_fpu_activate is called when do vcpu_reset. So it seems no >> need to call fpu_activate() here again.
Hi Paolo
The check in kvm_update_cpuid of fpu is strange since nothing relies on cpuid now. How about the following change?
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index bbbaa80..da4e6ad 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -114,9 +114,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) if (best && (best->eax & (F(XSAVES) | F(XSAVEC)))) best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
- if (use_eager_fpu()) - kvm_x86_ops->fpu_activate(vcpu); - /* * The existing code assumes virtual address is 48-bit in the canonical * address checks; exit if it is ever changed. diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9b7798c..8f57335 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7453,6 +7453,9 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) vcpu->arch.regs_avail = ~0; vcpu->arch.regs_dirty = ~0;
+ if (use_eager_fpu()) + kvm_x86_ops->fpu_activate(vcpu); + kvm_x86_ops->vcpu_reset(vcpu, init_event); }
-- best regards yang
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