KVM: x86 emulator: define callbacks for using the guest fpu within the emulator

Needed for emulating fpu instructions.
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -158,6 +158,8 @@ struct x86_emulate_ops {
 	int (*set_dr)(int dr, unsigned long value, struct kvm_vcpu *vcpu);
 	int (*set_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
 	int (*get_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata);
+	void (*get_fpu)(struct x86_emulate_ctxt *ctxt); /* disables preempt */
+	void (*put_fpu)(struct x86_emulate_ctxt *ctxt); /* reenables preempt */
 };
 
 /* Type, address-of, and value of an instruction's operand. */

arch/x86/kvm/x86.c

@@ -4281,6 +4281,22 @@ static void emulator_set_segment_selector(u16 sel, int seg,
 	kvm_set_segment(vcpu, &kvm_seg, seg);
 }
 
+static void emulator_get_fpu(struct x86_emulate_ctxt *ctxt)
+{
+	preempt_disable();
+	kvm_load_guest_fpu(ctxt->vcpu);
+	/*
+	 * CR0.TS may reference the host fpu state, not the guest fpu state,
+	 * so it may be clear at this point.
+	 */
+	clts();
+}
+
+static void emulator_put_fpu(struct x86_emulate_ctxt *ctxt)
+{
+	preempt_enable();
+}
+
 static struct x86_emulate_ops emulate_ops = {
 	.read_std            = kvm_read_guest_virt_system,
 	.write_std           = kvm_write_guest_virt_system,
@@ -4304,6 +4320,8 @@ static struct x86_emulate_ops emulate_ops = {
 	.set_dr              = emulator_set_dr,
 	.set_msr             = kvm_set_msr,
 	.get_msr             = kvm_get_msr,
+	.get_fpu             = emulator_get_fpu,
+	.put_fpu             = emulator_put_fpu,
 };
 
 static void cache_all_regs(struct kvm_vcpu *vcpu)