| Message ID | 1544610573-28446-6-git-send-email-andrew.murray@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Support perf event modifiers :G and :H | expand |
On 12/12/2018 10:29, Andrew Murray wrote: > Enable/disable event counters as appropriate when entering and exiting > the guest to enable support for guest or host only event counting. > > For both VHE and non-VHE we switch the counters between host/guest at > EL2. EL2 is filtered out by the PMU when we are using the :G modifier. > > The PMU may be on when we change which counters are enabled however > we avoid adding an isb as we instead rely on existing context > synchronisation events: the isb in kvm_arm_vhe_guest_exit for VHE and > the eret from the hvc in kvm_call_hyp. > > Signed-off-by: Andrew Murray <andrew.murray@arm.com> > --- > arch/arm64/kvm/hyp/switch.c | 52 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 52 insertions(+) > > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c > index d496ef5..9732ef7 100644 > --- a/arch/arm64/kvm/hyp/switch.c > +++ b/arch/arm64/kvm/hyp/switch.c > @@ -373,6 +373,46 @@ static bool __hyp_text __hyp_switch_fpsimd(struct kvm_vcpu *vcpu) > return true; > } > > +static bool __hyp_text __pmu_switch_to_guest(struct kvm_cpu_context *host_ctxt) > +{ > + struct kvm_host_data *host; > + struct kvm_pmu_events *pmu; > + u32 clr, set; > + > + host = container_of(host_ctxt, struct kvm_host_data, host_ctxt); > + pmu = &host->pmu_events; > + > + clr = pmu->events_host & ~pmu->events_guest; > + set = pmu->events_guest & ~pmu->events_host; It may make sense to add in a comment explaining why we only set: events_guest & ~events_host Either way: Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
On Wed, Dec 12, 2018 at 10:53:35AM +0000, Suzuki K Poulose wrote: > > > On 12/12/2018 10:29, Andrew Murray wrote: > > Enable/disable event counters as appropriate when entering and exiting > > the guest to enable support for guest or host only event counting. > > > > For both VHE and non-VHE we switch the counters between host/guest at > > EL2. EL2 is filtered out by the PMU when we are using the :G modifier. > > > > The PMU may be on when we change which counters are enabled however > > we avoid adding an isb as we instead rely on existing context > > synchronisation events: the isb in kvm_arm_vhe_guest_exit for VHE and > > the eret from the hvc in kvm_call_hyp. > > > > Signed-off-by: Andrew Murray <andrew.murray@arm.com> > > --- > > arch/arm64/kvm/hyp/switch.c | 52 +++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 52 insertions(+) > > > > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c > > index d496ef5..9732ef7 100644 > > --- a/arch/arm64/kvm/hyp/switch.c > > +++ b/arch/arm64/kvm/hyp/switch.c > > @@ -373,6 +373,46 @@ static bool __hyp_text __hyp_switch_fpsimd(struct kvm_vcpu *vcpu) > > return true; > > } > > +static bool __hyp_text __pmu_switch_to_guest(struct kvm_cpu_context *host_ctxt) > > +{ > > + struct kvm_host_data *host; > > + struct kvm_pmu_events *pmu; > > + u32 clr, set; > > + > > + host = container_of(host_ctxt, struct kvm_host_data, host_ctxt); > > + pmu = &host->pmu_events; > > + > > + clr = pmu->events_host & ~pmu->events_guest; > > + set = pmu->events_guest & ~pmu->events_host; > > It may make sense to add in a comment explaining why we only set: > > events_guest & ~events_host > Yes I'll add a comment, especially as I've just spend 5 minutes trying to remember why I did this. Instead of assigning 'pmu->events_guest & ~pmu->events_host' to 'set' we could have just assigned 'pmu->events_guest'. However consider the scenario where an event is enabled for both host and guest - this would have resulted in us always writing the (already set) bit to the system register. Therefore with my approach we can potentially avoid any system register writes on a hypervisor switch when the only events enabled are those for both host and guest. Thanks, Andrew Murray > Either way: > > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c index d496ef5..9732ef7 100644 --- a/arch/arm64/kvm/hyp/switch.c +++ b/arch/arm64/kvm/hyp/switch.c @@ -373,6 +373,46 @@ static bool __hyp_text __hyp_switch_fpsimd(struct kvm_vcpu *vcpu) return true; } +static bool __hyp_text __pmu_switch_to_guest(struct kvm_cpu_context *host_ctxt) +{ + struct kvm_host_data *host; + struct kvm_pmu_events *pmu; + u32 clr, set; + + host = container_of(host_ctxt, struct kvm_host_data, host_ctxt); + pmu = &host->pmu_events; + + clr = pmu->events_host & ~pmu->events_guest; + set = pmu->events_guest & ~pmu->events_host; + + if (clr) + write_sysreg(clr, pmcntenclr_el0); + + if (set) + write_sysreg(set, pmcntenset_el0); + + return (clr || set); +} + +static void __hyp_text __pmu_switch_to_host(struct kvm_cpu_context *host_ctxt) +{ + struct kvm_host_data *host; + struct kvm_pmu_events *pmu; + u32 clr, set; + + host = container_of(host_ctxt, struct kvm_host_data, host_ctxt); + pmu = &host->pmu_events; + + clr = pmu->events_guest & ~pmu->events_host; + set = pmu->events_host & ~pmu->events_guest; + + if (clr) + write_sysreg(clr, pmcntenclr_el0); + + if (set) + write_sysreg(set, pmcntenset_el0); +} + /* * Return true when we were able to fixup the guest exit and should return to * the guest, false when we should restore the host state and return to the @@ -488,12 +528,15 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu) { struct kvm_cpu_context *host_ctxt; struct kvm_cpu_context *guest_ctxt; + bool pmu_switch_needed; u64 exit_code; host_ctxt = vcpu->arch.host_cpu_context; host_ctxt->__hyp_running_vcpu = vcpu; guest_ctxt = &vcpu->arch.ctxt; + pmu_switch_needed = __pmu_switch_to_guest(host_ctxt); + sysreg_save_host_state_vhe(host_ctxt); __activate_traps(vcpu); @@ -524,6 +567,9 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu) __debug_switch_to_host(vcpu); + if (pmu_switch_needed) + __pmu_switch_to_host(host_ctxt); + return exit_code; } @@ -532,6 +578,7 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu) { struct kvm_cpu_context *host_ctxt; struct kvm_cpu_context *guest_ctxt; + bool pmu_switch_needed; u64 exit_code; vcpu = kern_hyp_va(vcpu); @@ -540,6 +587,8 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu) host_ctxt->__hyp_running_vcpu = vcpu; guest_ctxt = &vcpu->arch.ctxt; + pmu_switch_needed = __pmu_switch_to_guest(host_ctxt); + __sysreg_save_state_nvhe(host_ctxt); __activate_traps(vcpu); @@ -586,6 +635,9 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu) */ __debug_switch_to_host(vcpu); + if (pmu_switch_needed) + __pmu_switch_to_host(host_ctxt); + return exit_code; }
Enable/disable event counters as appropriate when entering and exiting the guest to enable support for guest or host only event counting. For both VHE and non-VHE we switch the counters between host/guest at EL2. EL2 is filtered out by the PMU when we are using the :G modifier. The PMU may be on when we change which counters are enabled however we avoid adding an isb as we instead rely on existing context synchronisation events: the isb in kvm_arm_vhe_guest_exit for VHE and the eret from the hvc in kvm_call_hyp. Signed-off-by: Andrew Murray <andrew.murray@arm.com> --- arch/arm64/kvm/hyp/switch.c | 52 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+)