KVM: vPMU: Fill get_msr MSR_CORE_PERF_GLOBAL_OVF_CTRL w/ 0

SDM section 18.2.3 mentioned that:

  "IA32_PERF_GLOBAL_OVF_CTL MSR allows software to clear overflow indicator(s) of
   any general-purpose or fixed-function counters via a single WRMSR."

It is R/W mentioned by SDM, we read this msr on bare-metal during perf testing,
the value is always 0 for ICX/SKX boxes on hands. Let's fill get_msr
MSR_CORE_PERF_GLOBAL_OVF_CTRL w/ 0 as hardware behavior and drop
global_ovf_ctrl variable.

Tested-by: Like Xu <likexu@tencent.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1634631160-67276-2-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -499,7 +499,6 @@ struct kvm_pmu {
 	u64 fixed_ctr_ctrl;
 	u64 global_ctrl;
 	u64 global_status;
-	u64 global_ovf_ctrl;
 	u64 counter_bitmask[2];
 	u64 global_ctrl_mask;
 	u64 global_ovf_ctrl_mask;

arch/x86/kvm/vmx/pmu_intel.c

@@ -365,7 +365,7 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = pmu->global_ctrl;
 		return 0;
 	case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
-		msr_info->data = pmu->global_ovf_ctrl;
+		msr_info->data = 0;
 		return 0;
 	default:
 		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
@@ -423,7 +423,6 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (!(data & pmu->global_ovf_ctrl_mask)) {
 			if (!msr_info->host_initiated)
 				pmu->global_status &= ~data;
-			pmu->global_ovf_ctrl = data;
 			return 0;
 		}
 		break;
@@ -588,8 +587,7 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
 		pmc->counter = 0;
 	}
 
-	pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status =
+	pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status = 0;
-		pmu->global_ovf_ctrl = 0;
 
 	intel_pmu_release_guest_lbr_event(vcpu);
 }