With VHE different exception levels are used between the host (EL2) and
guest (EL1) with a shared exception level for userpace (EL0). We can take
advantage of this and use the PMU's exception level filtering to avoid
enabling/disabling counters in the world-switch code. Instead we just
modify the counter type to include or exclude EL0 at vcpu_{load,put} time.
We also ensure that trapped PMU system register writes do not re-enable
EL0 when reconfiguring the backing perf events.
This approach completely avoids blackout windows seen with !VHE.
Suggested-by: Christoffer Dall <christoffer.dall@xxxxxxx>
Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm/include/asm/kvm_host.h | 3 ++
arch/arm64/include/asm/kvm_host.h | 5 +-
arch/arm64/kernel/perf_event.c | 6 ++-
arch/arm64/kvm/pmu.c | 87 ++++++++++++++++++++++++++++++-
arch/arm64/kvm/sys_regs.c | 3 ++
virt/kvm/arm/arm.c | 2 +
6 files changed, 102 insertions(+), 4 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 356f72b3643c..1adfe35ba1eb 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -365,6 +365,9 @@ static inline void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) {}
+static inline void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu) {}
+static inline void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu) {}
+
static inline void kvm_arm_vhe_guest_enter(void) {}
static inline void kvm_arm_vhe_guest_exit(void) {}
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a3bfb75f0be9..4f290dad3a48 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -528,7 +528,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
{
- return attr->exclude_host;
+ return (!has_vhe() && attr->exclude_host);
}
#ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
@@ -542,6 +542,9 @@ void kvm_clr_pmu_events(u32 clr);
void __pmu_switch_to_host(struct kvm_cpu_context *host_ctxt);
bool __pmu_switch_to_guest(struct kvm_cpu_context *host_ctxt);
+
+void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
+void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
#else
static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
static inline void kvm_clr_pmu_events(u32 clr) {}
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 6bb28aaf5aea..314b1adedf06 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -847,8 +847,12 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
* with other architectures (x86 and Power).
*/
if (is_kernel_in_hyp_mode()) {
- if (!attr->exclude_kernel)
+ if (!attr->exclude_kernel && !attr->exclude_host)
config_base |= ARMV8_PMU_INCLUDE_EL2;
+ if (attr->exclude_guest)
+ config_base |= ARMV8_PMU_EXCLUDE_EL1;
+ if (attr->exclude_host)
+ config_base |= ARMV8_PMU_EXCLUDE_EL0;
} else {
if (!attr->exclude_hv && !attr->exclude_host)
config_base |= ARMV8_PMU_INCLUDE_EL2;
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 48949f0cdba0..3407a529e116 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -8,11 +8,19 @@
#include <asm/kvm_hyp.h>
/*
- * Given the exclude_{host,guest} attributes, determine if we are going
- * to need to switch counters at guest entry/exit.
+ * Given the perf event attributes and system type, determine
+ * if we are going to need to switch counters at guest entry/exit.
*/
static bool kvm_pmu_switch_needed(struct perf_event_attr *attr)
{
+ /**
+ * With VHE the guest kernel runs at EL1 and the host at EL2,
+ * where user (EL0) is excluded then we have no reason to switch
+ * counters.
+ */
+ if (has_vhe() && attr->exclude_user)
+ return false;
+
/* Only switch if attributes are different */
return (attr->exclude_host != attr->exclude_guest);
}
@@ -83,3 +91,78 @@ void __hyp_text __pmu_switch_to_host(struct kvm_cpu_context *host_ctxt)
write_sysreg(pmu->events_host, pmcntenset_el0);
}
+/*
+ * Modify ARMv8 PMU events to include EL0 counting
+ */
+static void kvm_vcpu_pmu_enable_el0(unsigned long events)
+{
+ u64 typer;
+ u32 counter;
+
+ for_each_set_bit(counter, &events, 32) {
+ write_sysreg(counter, pmselr_el0);
+ isb();
+ typer = read_sysreg(pmxevtyper_el0) & ~ARMV8_PMU_EXCLUDE_EL0;
+ write_sysreg(typer, pmxevtyper_el0);
+ isb();
+ }
+}
+
+/*
+ * Modify ARMv8 PMU events to exclude EL0 counting
+ */
+static void kvm_vcpu_pmu_disable_el0(unsigned long events)
+{
+ u64 typer;
+ u32 counter;
+
+ for_each_set_bit(counter, &events, 32) {
+ write_sysreg(counter, pmselr_el0);
+ isb();
+ typer = read_sysreg(pmxevtyper_el0) | ARMV8_PMU_EXCLUDE_EL0;
+ write_sysreg(typer, pmxevtyper_el0);
+ isb();
+ }
+}
+
+/*
+ * On VHE ensure that only guest events have EL0 counting enabled
+ */
+void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpu_context *host_ctxt;
+ struct kvm_host_data *host;
+ u32 events_guest, events_host;
+
+ if (!has_vhe())
+ return;
+
+ host_ctxt = vcpu->arch.host_cpu_context;
+ host = container_of(host_ctxt, struct kvm_host_data, host_ctxt);
+ events_guest = host->pmu_events.events_guest;
+ events_host = host->pmu_events.events_host;
+
+ kvm_vcpu_pmu_enable_el0(events_guest);
+ kvm_vcpu_pmu_disable_el0(events_host);
+}
+
+/*
+ * On VHE ensure that only guest host have EL0 counting enabled
+ */
+void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpu_context *host_ctxt;
+ struct kvm_host_data *host;
+ u32 events_guest, events_host;
+
+ if (!has_vhe())
+ return;
+
+ host_ctxt = vcpu->arch.host_cpu_context;
+ host = container_of(host_ctxt, struct kvm_host_data, host_ctxt);
+ events_guest = host->pmu_events.events_guest;
+ events_host = host->pmu_events.events_host;
+
+ kvm_vcpu_pmu_enable_el0(events_host);
+ kvm_vcpu_pmu_disable_el0(events_guest);
+}
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 539feecda5b8..c7fa47ad2387 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -695,6 +695,7 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
val |= p->regval & ARMV8_PMU_PMCR_MASK;
__vcpu_sys_reg(vcpu, PMCR_EL0) = val;
kvm_pmu_handle_pmcr(vcpu, val);
+ kvm_vcpu_pmu_restore_guest(vcpu);
} else {
/* PMCR.P & PMCR.C are RAZ */
val = __vcpu_sys_reg(vcpu, PMCR_EL0)
@@ -850,6 +851,7 @@ static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (p->is_write) {
kvm_pmu_set_counter_event_type(vcpu, p->regval, idx);
__vcpu_sys_reg(vcpu, reg) = p->regval & ARMV8_PMU_EVTYPE_MASK;
+ kvm_vcpu_pmu_restore_guest(vcpu);
} else {
p->regval = __vcpu_sys_reg(vcpu, reg) & ARMV8_PMU_EVTYPE_MASK;
}
@@ -875,6 +877,7 @@ static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
/* accessing PMCNTENSET_EL0 */
__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) |= val;
kvm_pmu_enable_counter(vcpu, val);
+ kvm_vcpu_pmu_restore_guest(vcpu);
} else {
/* accessing PMCNTENCLR_EL0 */
__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) &= ~val;
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 6bcda52c0ea6..d805bb470dda 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -382,6 +382,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
kvm_timer_vcpu_load(vcpu);
kvm_vcpu_load_sysregs(vcpu);
kvm_arch_vcpu_load_fp(vcpu);
+ kvm_vcpu_pmu_restore_guest(vcpu);
if (single_task_running())
vcpu_clear_wfe_traps(vcpu);
@@ -395,6 +396,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
kvm_vcpu_put_sysregs(vcpu);
kvm_timer_vcpu_put(vcpu);
kvm_vgic_put(vcpu);
+ kvm_vcpu_pmu_restore_host(vcpu);
vcpu->cpu = -1;
--
2.21.0
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