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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