Revert "KVM: nVMX: Expose load IA32_PERF_GLOBAL_CTRL VM-{Entry,Exit} control"

This reverts commit 03a8871a.

Since commit 03a8871a ("KVM: nVMX: Expose load IA32_PERF_GLOBAL_CTRL
VM-{Entry,Exit} control"), KVM has taken ownership of the "load
IA32_PERF_GLOBAL_CTRL" VMX entry/exit control bits, trying to set these
bits in the IA32_VMX_TRUE_{ENTRY,EXIT}_CTLS MSRs if the guest's CPUID
supports the architectural PMU (CPUID[EAX=0Ah].EAX[7:0]=1), and clear
otherwise.

This was a misguided attempt at mimicking what commit 5f76f6f5
("KVM: nVMX: Do not expose MPX VMX controls when guest MPX disabled",
2018-10-01) did for MPX.  However, that commit was a workaround for
another KVM bug and not something that should be imitated.  Mucking with
the VMX MSRs creates a subtle, difficult to maintain ABI as KVM must
ensure that any internal changes, e.g. to how KVM handles _any_ guest
CPUID changes, yield the same functional result.  Therefore, KVM's policy
is to let userspace have full control of the guest vCPU model so long
as the host kernel is not at risk.

Now that KVM really truly ensures kvm_set_msr() will succeed by loading
PERF_GLOBAL_CTRL if and only if it exists, revert KVM's misguided and
roundabout behavior.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[sean: make it a pure revert]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220722224409.1336532-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -4824,28 +4824,6 @@ int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
 	return 0;
 }
 
-void nested_vmx_pmu_refresh(struct kvm_vcpu *vcpu,
-			    bool vcpu_has_perf_global_ctrl)
-{
-	struct vcpu_vmx *vmx;
-
-	if (!nested_vmx_allowed(vcpu))
-		return;
-
-	vmx = to_vmx(vcpu);
-	if (vcpu_has_perf_global_ctrl) {
-		vmx->nested.msrs.entry_ctls_high |=
-				VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
-		vmx->nested.msrs.exit_ctls_high |=
-				VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
-	} else {
-		vmx->nested.msrs.entry_ctls_high &=
-				~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
-		vmx->nested.msrs.exit_ctls_high &=
-				~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
-	}
-}
-
 static int nested_vmx_get_vmptr(struct kvm_vcpu *vcpu, gpa_t *vmpointer,
 				int *ret)
 {

arch/x86/kvm/vmx/nested.h

@@ -32,8 +32,6 @@ int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
 int vmx_get_vmx_msr(struct nested_vmx_msrs *msrs, u32 msr_index, u64 *pdata);
 int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
 			u32 vmx_instruction_info, bool wr, int len, gva_t *ret);
-void nested_vmx_pmu_refresh(struct kvm_vcpu *vcpu,
-			    bool vcpu_has_perf_global_ctrl);
 void nested_mark_vmcs12_pages_dirty(struct kvm_vcpu *vcpu);
 bool nested_vmx_check_io_bitmaps(struct kvm_vcpu *vcpu, unsigned int port,
 				 int size);

arch/x86/kvm/vmx/pmu_intel.c

@@ -592,9 +592,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	bitmap_set(pmu->all_valid_pmc_idx,
 		INTEL_PMC_MAX_GENERIC, pmu->nr_arch_fixed_counters);
 
-	nested_vmx_pmu_refresh(vcpu,
-			       intel_is_valid_msr(vcpu, MSR_CORE_PERF_GLOBAL_CTRL));
-
 	if (cpuid_model_is_consistent(vcpu))
 		x86_perf_get_lbr(&lbr_desc->records);
 	else