KVM: Activate fpu on clts

Assume that if the guest executes clts, it knows what it's doing, and load the
guest fpu to prevent an #NM exception.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

4 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d73ed48587e4..7ebf9fe670cd 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -511,6 +511,7 @@ struct kvm_x86_ops {
         void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
         unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
         void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
+        void (*fpu_activate)(struct kvm_vcpu *vcpu);
         void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
 
         void (*tlb_flush)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a281368c3b96..800208a60a51 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1259,12 +1259,17 @@ static int ud_interception(struct vcpu_svm *svm)
         return 1;
 }
 
-static int nm_interception(struct vcpu_svm *svm)
+static void svm_fpu_activate(struct kvm_vcpu *vcpu)
 {
+        struct vcpu_svm *svm = to_svm(vcpu);
         svm->vmcb->control.intercept_exceptions &= ~(1 << NM_VECTOR);
         svm->vcpu.fpu_active = 1;
         update_cr0_intercept(svm);
+}
 
+static int nm_interception(struct vcpu_svm *svm)
+{
+        svm_fpu_activate(&svm->vcpu);
         return 1;
 }
 
@@ -2977,6 +2982,7 @@ static struct kvm_x86_ops svm_x86_ops = {
         .cache_reg = svm_cache_reg,
         .get_rflags = svm_get_rflags,
         .set_rflags = svm_set_rflags,
+        .fpu_activate = svm_fpu_activate,
         .fpu_deactivate = svm_fpu_deactivate,
 
         .tlb_flush = svm_flush_tlb,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b7e812e9c299..fad871cbed19 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3002,6 +3002,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
                 vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
                 trace_kvm_cr_write(0, kvm_read_cr0(vcpu));
                 skip_emulated_instruction(vcpu);
+                vmx_fpu_activate(vcpu);
                 return 1;
         case 1: /*mov from cr*/
                 switch (cr) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c61ec9c69267..4db0c8a9082e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3269,6 +3269,7 @@ int emulate_invlpg(struct kvm_vcpu *vcpu, gva_t address)
 int emulate_clts(struct kvm_vcpu *vcpu)
 {
         kvm_x86_ops->set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
+        kvm_x86_ops->fpu_activate(vcpu);
         return X86EMUL_CONTINUE;
 }