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>

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);

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,

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) {

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;
 }