diff -r 962b18bbd6d9 kernel/kvm.h
--- a/kernel/kvm.h	Thu Feb 15 13:58:59 2007 +0000
+++ b/kernel/kvm.h	Thu Feb 15 13:23:56 2007 -0600
@@ -17,6 +17,7 @@
 #include <linux/kvm_para.h>
 
 #define CR0_PE_MASK (1ULL << 0)
+#define CR0_MP_MASK (1ULL << 1)
 #define CR0_TS_MASK (1ULL << 3)
 #define CR0_NE_MASK (1ULL << 5)
 #define CR0_WP_MASK (1ULL << 16)
@@ -263,6 +264,7 @@ struct kvm_vcpu {
 
 	struct kvm_guest_debug guest_debug;
 
+	int fx_active;
 	char fx_buf[FX_BUF_SIZE];
 	char *host_fx_image;
 	char *guest_fx_image;
diff -r 962b18bbd6d9 kernel/kvm_main.c
--- a/kernel/kvm_main.c	Thu Feb 15 13:58:59 2007 +0000
+++ b/kernel/kvm_main.c	Thu Feb 15 13:27:17 2007 -0600
@@ -404,6 +404,7 @@ void set_cr0(struct kvm_vcpu *vcpu, unsi
 
 	}
 
+	vcpu->fx_active = !((cr0 & CR0_TS_MASK) && (cr0 & CR0_MP_MASK));
 	kvm_arch_ops->set_cr0(vcpu, cr0);
 	vcpu->cr0 = cr0;
 
@@ -530,6 +531,7 @@ void fx_init(struct kvm_vcpu *vcpu)
 	fx_image->mxcsr = 0x1f80;
 	memset(vcpu->guest_fx_image + sizeof(struct fx_image_s),
 	       0, FX_IMAGE_SIZE - sizeof(struct fx_image_s));
+	vcpu->fx_active = 1;
 }
 EXPORT_SYMBOL_GPL(fx_init);
 
diff -r 962b18bbd6d9 kernel/svm.c
--- a/kernel/svm.c	Thu Feb 15 13:58:59 2007 +0000
+++ b/kernel/svm.c	Thu Feb 15 13:30:52 2007 -0600
@@ -1461,8 +1461,10 @@ again:
 		load_db_regs(vcpu->svm->db_regs);
 	}
 
-	fx_save(vcpu->host_fx_image);
-	fx_restore(vcpu->guest_fx_image);
+	if (vcpu->fx_active) {
+		fx_save(vcpu->host_fx_image);
+		fx_restore(vcpu->guest_fx_image);
+	}
 
 	asm volatile (
 #ifdef CONFIG_X86_64
@@ -1573,8 +1575,10 @@ again:
 #endif
 		: "cc", "memory" );
 
-	fx_save(vcpu->guest_fx_image);
-	fx_restore(vcpu->host_fx_image);
+	if (vcpu->fx_active) {
+		fx_save(vcpu->guest_fx_image);
+		fx_restore(vcpu->host_fx_image);
+	}
 
 	if ((vcpu->svm->vmcb->save.dr7 & 0xff))
 		load_db_regs(vcpu->svm->host_db_regs);
diff -r 962b18bbd6d9 kernel/vmx.c
--- a/kernel/vmx.c	Thu Feb 15 13:58:59 2007 +0000
+++ b/kernel/vmx.c	Thu Feb 15 13:30:20 2007 -0600
@@ -1764,8 +1764,10 @@ again:
 	if (vcpu->guest_debug.enabled)
 		kvm_guest_debug_pre(vcpu);
 
-	fx_save(vcpu->host_fx_image);
-	fx_restore(vcpu->guest_fx_image);
+	if (vcpu->fx_active) {
+		fx_save(vcpu->host_fx_image);
+		fx_restore(vcpu->guest_fx_image);
+	}
 
 	save_msrs(vcpu->host_msrs, vcpu->nmsrs);
 	load_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
@@ -1894,8 +1896,11 @@ again:
 	save_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
 	load_msrs(vcpu->host_msrs, NR_BAD_MSRS);
 
-	fx_save(vcpu->guest_fx_image);
-	fx_restore(vcpu->host_fx_image);
+	if (vcpu->fx_active) {
+		fx_save(vcpu->guest_fx_image);
+		fx_restore(vcpu->host_fx_image);
+	}
+
 	vcpu->interrupt_window_open = (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0;
 
 	asm ("mov %0, %%ds; mov %0, %%es" : : "r"(__USER_DS));