KVM: x86/pmu: Zero out pmu->all_valid_pmc_idx each time it's refreshed

The kvm_pmu_refresh() may be called repeatedly (e.g. configure guest
CPUID repeatedly or update MSR_IA32_PERF_CAPABILITIES) and each
call will use the last pmu->all_valid_pmc_idx value, with the residual
bits introducing additional overhead later in the vPMU emulation.

Fixes: b35e5548 ("KVM: x86/vPMU: Add lazy mechanism to release perf_event per vPMC")
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20230404071759.75376-1-likexu@tencent.comSigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/pmu.c

@@ -589,6 +589,7 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
  */
 void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
 {
+	bitmap_zero(vcpu_to_pmu(vcpu)->all_valid_pmc_idx, X86_PMC_IDX_MAX);
 	static_call(kvm_x86_pmu_refresh)(vcpu);
 }