KVM: x86: Move MSR_IA32_PRED_CMD WRMSR emulation to common code

Dedup the handling of MSR_IA32_PRED_CMD across VMX and SVM by moving the
logic to kvm_set_msr_common().  Now that the MSR interception toggling is
handled as part of setting guest CPUID, the VMX and SVM paths are
identical.

Opportunistically massage the code to make it a wee bit denser.

Link: https://lore.kernel.org/r/20230322011440.2195485-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/svm/svm.c

@@ -2942,20 +2942,6 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		 */
 		set_msr_interception(vcpu, svm->msrpm, MSR_IA32_SPEC_CTRL, 1, 1);
 		break;
-	case MSR_IA32_PRED_CMD:
-		if (!msr->host_initiated &&
-		    !guest_has_pred_cmd_msr(vcpu))
-			return 1;
-
-		if (data & ~PRED_CMD_IBPB)
-			return 1;
-		if (!boot_cpu_has(X86_FEATURE_IBPB))
-			return 1;
-		if (!data)
-			break;
-
-		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
-		break;
 	case MSR_AMD64_VIRT_SPEC_CTRL:
 		if (!msr->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_VIRT_SSBD))

arch/x86/kvm/vmx/vmx.c

@@ -2285,20 +2285,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (data & ~(TSX_CTRL_RTM_DISABLE | TSX_CTRL_CPUID_CLEAR))
 			return 1;
 		goto find_uret_msr;
-	case MSR_IA32_PRED_CMD:
-		if (!msr_info->host_initiated &&
-		    !guest_has_pred_cmd_msr(vcpu))
-			return 1;
-
-		if (data & ~PRED_CMD_IBPB)
-			return 1;
-		if (!boot_cpu_has(X86_FEATURE_IBPB))
-			return 1;
-		if (!data)
-			break;
-
-		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
-		break;
 	case MSR_IA32_CR_PAT:
 		if (!kvm_pat_valid(data))
 			return 1;

arch/x86/kvm/x86.c

@@ -3617,6 +3617,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.perf_capabilities = data;
 		kvm_pmu_refresh(vcpu);
 		return 0;
+	case MSR_IA32_PRED_CMD:
+		if (!msr_info->host_initiated && !guest_has_pred_cmd_msr(vcpu))
+			return 1;
+
+		if (!boot_cpu_has(X86_FEATURE_IBPB) || (data & ~PRED_CMD_IBPB))
+			return 1;
+		if (!data)
+			break;
+
+		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
+		break;
 	case MSR_EFER:
 		return set_efer(vcpu, msr_info);
 	case MSR_K7_HWCR: