KVM: x86: Allow HWCR.McStatusWrEn to be cleared once set

When HWCR is set to 0, store 0 in vcpu->arch.msr_hwcr.

Fixes: 191c813 ("x86/kvm: Implement HWCR support")
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20230929230246.1954854-2-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: jsmattsonjr

arch/x86/kvm/x86.c

@@ -3791,12 +3791,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		data &= ~(u64)0x8;	/* ignore TLB cache disable */
 
 		/* Handle McStatusWrEn */
-		if (data == BIT_ULL(18)) {
-			vcpu->arch.msr_hwcr = data;
-		} else if (data != 0) {
+		if (data & ~BIT_ULL(18)) {
 			kvm_pr_unimpl_wrmsr(vcpu, msr, data);
 			return 1;
 		}
+		vcpu->arch.msr_hwcr = data;
 		break;
 	case MSR_FAM10H_MMIO_CONF_BASE:
 		if (data != 0) {