On 8/1/2024 12:58 PM, Mingwei Zhang wrote:
> Allow writing to fixed counter selector if counter is exposed. If this
> fixed counter is filtered out, this counter won't be enabled on HW.
>
> Passthrough PMU implements the context switch at VM Enter/Exit boundary the
> guest value cannot be directly written to HW since the HW PMU is owned by
> the host. Introduce a new field fixed_ctr_ctrl_hw in kvm_pmu to cache the
> guest value. which will be assigne to HW at PMU context restore.
>
> Since passthrough PMU intercept writes to fixed counter selector, there is
> no need to read the value at pmu context save, but still clear the fix
> counter ctrl MSR and counters when switching out to host PMU.
>
> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
> Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
> Tested-by: Yongwei Ma <yongwei.ma@xxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/vmx/pmu_intel.c | 28 ++++++++++++++++++++++++----
> 2 files changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e5c288d4264f..93c17da8271d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -549,6 +549,7 @@ struct kvm_pmu {
> unsigned nr_arch_fixed_counters;
> unsigned available_event_types;
> u64 fixed_ctr_ctrl;
> + u64 fixed_ctr_ctrl_hw;
> u64 fixed_ctr_ctrl_mask;
> u64 global_ctrl;
> u64 global_status;
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index 0cd38c5632ee..c61936266cbd 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -34,6 +34,25 @@
>
> #define MSR_PMC_FULL_WIDTH_BIT (MSR_IA32_PMC0 - MSR_IA32_PERFCTR0)
>
> +static void reprogram_fixed_counters_in_passthrough_pmu(struct kvm_pmu *pmu, u64 data)
> +{
> + struct kvm_pmc *pmc;
> + u64 new_data = 0;
> + int i;
> +
> + for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
> + pmc = get_fixed_pmc(pmu, MSR_CORE_PERF_FIXED_CTR0 + i);
> + if (check_pmu_event_filter(pmc)) {
> + pmc->current_config = fixed_ctrl_field(data, i);
> + new_data |= (pmc->current_config << (i * 4));
Since we already have macro intel_fixed_bits_by_idx() to manipulate
fixed_cntr_ctrl, we 'd better to use it.
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 3dbeb41b85ab..0aa58bffb99d 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -44,7 +44,7 @@ static void
reprogram_fixed_counters_in_passthrough_pmu(struct kvm_pmu *pmu, u64
pmc = get_fixed_pmc(pmu, MSR_CORE_PERF_FIXED_CTR0 + i);
if (check_pmu_event_filter(pmc)) {
pmc->current_config = fixed_ctrl_field(data, i);
- new_data |= (pmc->current_config << (i * 4));
+ new_data |= intel_fixed_bits_by_idx(i,
pmc->current_config);
} else {
pmc->counter = 0;
}
> + } else {
> + pmc->counter = 0;
> + }
> + }
> + pmu->fixed_ctr_ctrl_hw = new_data;
> + pmu->fixed_ctr_ctrl = data;
> +}
> +
> static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
> {
> struct kvm_pmc *pmc;
> @@ -351,7 +370,9 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> if (data & pmu->fixed_ctr_ctrl_mask)
> return 1;
>
> - if (pmu->fixed_ctr_ctrl != data)
> + if (is_passthrough_pmu_enabled(vcpu))
> + reprogram_fixed_counters_in_passthrough_pmu(pmu, data);
> + else if (pmu->fixed_ctr_ctrl != data)
> reprogram_fixed_counters(pmu, data);
> break;
> case MSR_IA32_PEBS_ENABLE:
> @@ -820,13 +841,12 @@ static void intel_save_guest_pmu_context(struct kvm_vcpu *vcpu)
> if (pmu->global_status)
> wrmsrl(MSR_CORE_PERF_GLOBAL_OVF_CTRL, pmu->global_status);
>
> - rdmsrl(MSR_CORE_PERF_FIXED_CTR_CTRL, pmu->fixed_ctr_ctrl);
> /*
> * Clear hardware FIXED_CTR_CTRL MSR to avoid information leakage and
> * also avoid these guest fixed counters get accidentially enabled
> * during host running when host enable global ctrl.
> */
> - if (pmu->fixed_ctr_ctrl)
> + if (pmu->fixed_ctr_ctrl_hw)
> wrmsrl(MSR_CORE_PERF_FIXED_CTR_CTRL, 0);
> }
>
> @@ -844,7 +864,7 @@ static void intel_restore_guest_pmu_context(struct kvm_vcpu *vcpu)
> if (pmu->global_status & toggle)
> wrmsrl(MSR_CORE_PERF_GLOBAL_STATUS_SET, pmu->global_status & toggle);
>
> - wrmsrl(MSR_CORE_PERF_FIXED_CTR_CTRL, pmu->fixed_ctr_ctrl);
> + wrmsrl(MSR_CORE_PERF_FIXED_CTR_CTRL, pmu->fixed_ctr_ctrl_hw);
> }
>
> struct kvm_pmu_ops intel_pmu_ops __initdata = {
