On 7/31/2024 9:58 PM, Mingwei Zhang wrote:
> @@ -7295,6 +7299,46 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
> msrs[i].host, false);
> }
>
> +static void save_perf_global_ctrl_in_passthrough_pmu(struct vcpu_vmx *vmx)
> +{
> + struct kvm_pmu *pmu = vcpu_to_pmu(&vmx->vcpu);
> + int i;
> +
> + if (vm_exit_controls_get(vmx) & VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL) {
> + pmu->global_ctrl = vmcs_read64(GUEST_IA32_PERF_GLOBAL_CTRL);
As commented in patch 26, compared with MSR auto save/store area
approach, the exec control way needs one relatively expensive VMCS read
on every VM exit.
> + } else {
> + i = pmu->global_ctrl_slot_in_autostore;
> + pmu->global_ctrl = vmx->msr_autostore.guest.val[i].value;
> + }
> +}
> +
> +static void load_perf_global_ctrl_in_passthrough_pmu(struct vcpu_vmx *vmx)
> +{
> + struct kvm_pmu *pmu = vcpu_to_pmu(&vmx->vcpu);
> + u64 global_ctrl = pmu->global_ctrl;
> + int i;
> +
> + if (vm_entry_controls_get(vmx) & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) {
> + vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL, global_ctrl);
ditto.
We may optimize it by introducing a new flag pmu->global_ctrl_dirty and
update GUEST_IA32_PERF_GLOBAL_CTRL only when it's needed. But this
makes the code even more complicated.
> + } else {
> + i = pmu->global_ctrl_slot_in_autoload;
> + vmx->msr_autoload.guest.val[i].value = global_ctrl;
> + }
> +}
> +
> +static void __atomic_switch_perf_msrs_in_passthrough_pmu(struct vcpu_vmx *vmx)
> +{
> + load_perf_global_ctrl_in_passthrough_pmu(vmx);
> +}
> +
> +static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
> +{
> + if (is_passthrough_pmu_enabled(&vmx->vcpu))
> + __atomic_switch_perf_msrs_in_passthrough_pmu(vmx);
> + else
> + __atomic_switch_perf_msrs(vmx);
> +}
> +
> static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit)
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
