On Tue, May 14, 2024, Mi, Dapeng wrote: > > On 5/6/2024 1:29 PM, Mingwei Zhang wrote: > > Implement the save/restore of PMU state for pasthrough PMU in Intel. In > > passthrough mode, KVM owns exclusively the PMU HW when control flow goes to > > the scope of passthrough PMU. Thus, KVM needs to save the host PMU state > > and gains the full HW PMU ownership. On the contrary, host regains the > > ownership of PMU HW from KVM when control flow leaves the scope of > > passthrough PMU. > > > > Implement PMU context switches for Intel CPUs and opptunistically use > > rdpmcl() instead of rdmsrl() when reading counters since the former has > > lower latency in Intel CPUs. > > It looks rdpmcl() optimization is removed from this patch, right? The > description is not identical with code. That is correct. I was debugging this for a while and since we don't have rdpmcl_safe(), one of the bug cause rdpmc() to crash the kernel. Really don't like rdpmc(). But will add it back in next version. > > > > > > Co-developed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx> > > Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx> > > The commit tags doesn't follow the rules in Linux document, we need to > change it in next version. Will do. > > https://docs.kernel.org/process/submitting-patches.html#:~:text=Co%2Ddeveloped%2Dby%3A%20states,work%20on%20a%20single%20patch. > > > --- > > arch/x86/kvm/pmu.c | 46 ++++++++++++++++++++++++++++++++++++ > > arch/x86/kvm/vmx/pmu_intel.c | 41 +++++++++++++++++++++++++++++++- > > 2 files changed, 86 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > > index 782b564bdf96..13197472e31d 100644 > > --- a/arch/x86/kvm/pmu.c > > +++ b/arch/x86/kvm/pmu.c > > @@ -1068,14 +1068,60 @@ void kvm_pmu_passthrough_pmu_msrs(struct kvm_vcpu *vcpu) > > > > void kvm_pmu_save_pmu_context(struct kvm_vcpu *vcpu) > > { > > + struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > > + struct kvm_pmc *pmc; > > + u32 i; > > + > > lockdep_assert_irqs_disabled(); > > > > static_call_cond(kvm_x86_pmu_save_pmu_context)(vcpu); > > + > > + /* > > + * Clear hardware selector MSR content and its counter to avoid > > + * leakage and also avoid this guest GP counter get accidentally > > + * enabled during host running when host enable global ctrl. > > + */ > > + for (i = 0; i < pmu->nr_arch_gp_counters; i++) { > > + pmc = &pmu->gp_counters[i]; > > + rdmsrl(pmc->msr_counter, pmc->counter); > > I understood we want to use common code to manipulate PMU MSRs as much as > possible, but I don't think we should sacrifice performance. rdpmcl() has > better performance than rdmsrl(). If AMD CPUs doesn't support rdpmc > instruction, I think we should move this into vendor specific > xxx_save/restore_pmu_context helpers(). > > > > + rdmsrl(pmc->msr_eventsel, pmc->eventsel); > > + if (pmc->counter) > > + wrmsrl(pmc->msr_counter, 0); > > + if (pmc->eventsel) > > + wrmsrl(pmc->msr_eventsel, 0); > > + } > > + > > + for (i = 0; i < pmu->nr_arch_fixed_counters; i++) { > > + pmc = &pmu->fixed_counters[i]; > > + rdmsrl(pmc->msr_counter, pmc->counter); > > + if (pmc->counter) > > + wrmsrl(pmc->msr_counter, 0); > > + } > > } > > > > void kvm_pmu_restore_pmu_context(struct kvm_vcpu *vcpu) > > { > > + struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > > + struct kvm_pmc *pmc; > > + int i; > > + > > lockdep_assert_irqs_disabled(); > > > > static_call_cond(kvm_x86_pmu_restore_pmu_context)(vcpu); > > + > > + /* > > + * No need to zero out unexposed GP/fixed counters/selectors since RDPMC > > + * in this case will be intercepted. Accessing to these counters and > > + * selectors will cause #GP in the guest. > > + */ > > + for (i = 0; i < pmu->nr_arch_gp_counters; i++) { > > + pmc = &pmu->gp_counters[i]; > > + wrmsrl(pmc->msr_counter, pmc->counter); > > + wrmsrl(pmc->msr_eventsel, pmu->gp_counters[i].eventsel); > > + } > > + > > + for (i = 0; i < pmu->nr_arch_fixed_counters; i++) { > > + pmc = &pmu->fixed_counters[i]; > > + wrmsrl(pmc->msr_counter, pmc->counter); > > + } > > } > > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c > > index 7852ba25a240..a23cf9ca224e 100644 > > --- a/arch/x86/kvm/vmx/pmu_intel.c > > +++ b/arch/x86/kvm/vmx/pmu_intel.c > > @@ -572,7 +572,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) > > } > > > > for (i = 0; i < pmu->nr_arch_fixed_counters; i++) { > > - pmu->fixed_counters[i].msr_eventsel = MSR_CORE_PERF_FIXED_CTR_CTRL; > > + pmu->fixed_counters[i].msr_eventsel = 0; > Why to initialize msr_eventsel to 0 instead of the real MSR address here? > > pmu->fixed_counters[i].msr_counter = MSR_CORE_PERF_FIXED_CTR0 + i; > > } > > } > > @@ -799,6 +799,43 @@ static void intel_passthrough_pmu_msrs(struct kvm_vcpu *vcpu) > > vmx_set_intercept_for_msr(vcpu, MSR_CORE_PERF_GLOBAL_OVF_CTRL, MSR_TYPE_RW, msr_intercept); > > } > > > > +static void intel_save_guest_pmu_context(struct kvm_vcpu *vcpu) > > +{ > > + struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > > + > > + /* Global ctrl register is already saved at VM-exit. */ > > + rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, pmu->global_status); > > + /* Clear hardware MSR_CORE_PERF_GLOBAL_STATUS MSR, if non-zero. */ > > + 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) > > + wrmsrl(MSR_CORE_PERF_FIXED_CTR_CTRL, 0); > > +} > > + > > +static void intel_restore_guest_pmu_context(struct kvm_vcpu *vcpu) > > +{ > > + struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > > + u64 global_status, toggle; > > + > > + /* Clear host global_ctrl MSR if non-zero. */ > > + wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0); > > + rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, global_status); > > + toggle = pmu->global_status ^ global_status; > > + if (global_status & toggle) > > + wrmsrl(MSR_CORE_PERF_GLOBAL_OVF_CTRL, global_status & toggle); > > + 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); > > +} > > + > > struct kvm_pmu_ops intel_pmu_ops __initdata = { > > .rdpmc_ecx_to_pmc = intel_rdpmc_ecx_to_pmc, > > .msr_idx_to_pmc = intel_msr_idx_to_pmc, > > @@ -812,6 +849,8 @@ struct kvm_pmu_ops intel_pmu_ops __initdata = { > > .cleanup = intel_pmu_cleanup, > > .is_rdpmc_passthru_allowed = intel_is_rdpmc_passthru_allowed, > > .passthrough_pmu_msrs = intel_passthrough_pmu_msrs, > > + .save_pmu_context = intel_save_guest_pmu_context, > > + .restore_pmu_context = intel_restore_guest_pmu_context, > > .EVENTSEL_EVENT = ARCH_PERFMON_EVENTSEL_EVENT, > > .MAX_NR_GP_COUNTERS = KVM_INTEL_PMC_MAX_GENERIC, > > .MIN_NR_GP_COUNTERS = 1, >
