x86: KVM: add xsetbv to the emulator

To avoid hardcoding xsetbv length to '3' we need to support decoding it in
the emulator.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 6170ddf..bef3c3c 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4156,6 +4156,20 @@ static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
 	return rc;
 }
 
+static int em_xsetbv(struct x86_emulate_ctxt *ctxt)
+{
+	u32 eax, ecx, edx;
+
+	eax = reg_read(ctxt, VCPU_REGS_RAX);
+	edx = reg_read(ctxt, VCPU_REGS_RDX);
+	ecx = reg_read(ctxt, VCPU_REGS_RCX);
+
+	if (ctxt->ops->set_xcr(ctxt, ecx, ((u64)edx << 32) | eax))
+		return emulate_gp(ctxt, 0);
+
+	return X86EMUL_CONTINUE;
+}
+
 static bool valid_cr(int nr)
 {
 	switch (nr) {
@@ -4409,6 +4423,12 @@ static const struct opcode group7_rm1[] = {
 	N, N, N, N, N, N,
 };
 
+static const struct opcode group7_rm2[] = {
+	N,
+	II(ImplicitOps | Priv,			em_xsetbv,	xsetbv),
+	N, N, N, N, N, N,
+};
+
 static const struct opcode group7_rm3[] = {
 	DIP(SrcNone | Prot | Priv,		vmrun,		check_svme_pa),
 	II(SrcNone  | Prot | EmulateOnUD,	em_hypercall,	vmmcall),
@@ -4498,7 +4518,8 @@ static const struct group_dual group7 = { {
 }, {
 	EXT(0, group7_rm0),
 	EXT(0, group7_rm1),
-	N, EXT(0, group7_rm3),
+	EXT(0, group7_rm2),
+	EXT(0, group7_rm3),
 	II(SrcNone | DstMem | Mov,		em_smsw, smsw), N,
 	II(SrcMem16 | Mov | Priv,		em_lmsw, lmsw),
 	EXT(0, group7_rm7),