KVM: x86: Remove ordering check b/w MSR_PLATFORM_INFO and MISC_FEATURES_ENABLES

Drop KVM's odd restriction that disallows clearing CPUID_FAULT in
MSR_PLATFORM_INFO if CPL>0 CPUID faulting is enabled in
MSR_MISC_FEATURES_ENABLES.  KVM generally doesn't require specific
ordering when userspace sets MSRs, and the completely arbitrary order of
MSRs in emulated_msrs_all means that a userspace that uses KVM's list
verbatim could run afoul of the check.

Dropping the restriction obviously means that userspace could stuff a
nonsensical vCPU model, but that's the case all over KVM.  KVM typically
restricts userspace MSR writes only when it makes things easier for KVM
and/or userspace.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

Author: sean-jc

arch/x86/kvm/x86.c

@@ -4116,9 +4116,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.osvw.status = data;
 		break;
 	case MSR_PLATFORM_INFO:
-		if (!msr_info->host_initiated ||
-		    (!(data & MSR_PLATFORM_INFO_CPUID_FAULT) &&
-		     cpuid_fault_enabled(vcpu)))
+		if (!msr_info->host_initiated)
 			return 1;
 		vcpu->arch.msr_platform_info = data;
 		break;