KVM: X86: Introduce kvm_get_msr_feature()

Introduce kvm_get_msr_feature() to handle the msrs which are supported
by different vendors and sharing the same emulation logic.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

CVE-2018-3620
CVE-2018-3646

(cherry picked from commit 66421c1e)
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kvm/x86.c

@@ -1002,13 +1002,25 @@ static u32 msr_based_features[] = {
 
 static unsigned int num_msr_based_features;
 
+static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
+{
+	switch (msr->index) {
+	default:
+		if (kvm_x86_ops->get_msr_feature(msr))
+			return 1;
+	}
+	return 0;
+}
+
 static int do_get_msr_feature(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
 {
 	struct kvm_msr_entry msr;
+	int r;
 
 	msr.index = index;
-	if (kvm_x86_ops->get_msr_feature(&msr))
-		return 1;
+	r = kvm_get_msr_feature(&msr);
+	if (r)
+		return r;
 
 	*data = msr.data;
 
@@ -4170,7 +4182,7 @@ static void kvm_init_msr_list(void)
 		struct kvm_msr_entry msr;
 
 		msr.index = msr_based_features[i];
-		if (kvm_x86_ops->get_msr_feature(&msr))
+		if (kvm_get_msr_feature(&msr))
 			continue;
 
 		if (j < i)