Since many guests will never touch the PMU, they need not pay the cost of context swapping those registers.
Use the ownership enum from the previous commit to implement a simple state machine for PMU ownership. The PMU is always in one of three states: host owned, guest owned, or free.
A host owned state means all PMU registers are trapped coarsely by MDCR_EL2.TPM. In host owned state PMU partitioning is disabled and the PMU may not transition to a different state without intervention from the host.
A guest owned state means some PMU registers are untrapped under FGT controls. This is the only state in which context swaps take place.
A free state is the default partitioned state. It means no context swaps take place and KVM keeps the registers trapped. If a guest accesses the PMU registers in a free state, the PMU transitions to a guest owned state and KVM recalculates MDCR_EL2 to unset TPM.
Signed-off-by: Colton Lewis coltonlewis@google.com --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/include/asm/kvm_pmu.h | 18 ++++++++++++++++++ arch/arm64/kvm/debug.c | 2 +- arch/arm64/kvm/pmu-direct.c | 4 +++- arch/arm64/kvm/pmu.c | 24 ++++++++++++++++++++++++ arch/arm64/kvm/sys_regs.c | 24 ++++++++++++++++++++++-- 6 files changed, 69 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 21e32d7fa19b..f6803b57b648 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1453,6 +1453,7 @@ static inline bool kvm_system_needs_idmapped_vectors(void) return cpus_have_final_cap(ARM64_SPECTRE_V3A); }
+void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu); void kvm_init_host_debug_data(void); void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu); void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu); diff --git a/arch/arm64/include/asm/kvm_pmu.h b/arch/arm64/include/asm/kvm_pmu.h index 58c1219adf54..47cfff7ebc26 100644 --- a/arch/arm64/include/asm/kvm_pmu.h +++ b/arch/arm64/include/asm/kvm_pmu.h @@ -97,6 +97,11 @@ u64 kvm_pmu_guest_counter_mask(struct arm_pmu *pmu); void kvm_pmu_host_counters_enable(void); void kvm_pmu_host_counters_disable(void);
+bool kvm_pmu_regs_free(struct kvm_vcpu *vcpu); +bool kvm_pmu_regs_host_owned(struct kvm_vcpu *vcpu); +bool kvm_pmu_regs_guest_owned(struct kvm_vcpu *vcpu); +void kvm_pmu_regs_set_guest_owned(struct kvm_vcpu *vcpu); + u8 kvm_pmu_guest_num_counters(struct kvm_vcpu *vcpu); u8 kvm_pmu_hpmn(struct kvm_vcpu *vcpu); void kvm_pmu_load(struct kvm_vcpu *vcpu); @@ -168,6 +173,19 @@ static inline u8 kvm_pmu_guest_num_counters(struct kvm_vcpu *vcpu) { return 0; } +static inline bool kvm_pmu_regs_free(struct kvm_vcpu *vcpu) +{ + return false; +} +static inline bool kvm_pmu_regs_host_owned(struct kvm_vcpu *vcpu) +{ + return true; +} +static inline bool kvm_pmu_regs_guest_owned(struct kvm_vcpu *vcpu) +{ + return false; +} +static inline void kvm_pmu_regs_set_guest_owned(struct kvm_vcpu *vcpu) {} static inline u8 kvm_pmu_hpmn(struct kvm_vcpu *vcpu) { return 0; diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index fa8b4f846b68..128fa17b7a35 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -28,7 +28,7 @@ * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF) * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB) */ -static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu) +void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu) { preempt_disable();
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c index e21fdd274c2e..28d8540c5ed2 100644 --- a/arch/arm64/kvm/pmu-direct.c +++ b/arch/arm64/kvm/pmu-direct.c @@ -52,7 +52,8 @@ bool kvm_pmu_is_partitioned(struct arm_pmu *pmu) */ bool kvm_vcpu_pmu_is_partitioned(struct kvm_vcpu *vcpu) { - return kvm_pmu_is_partitioned(vcpu->kvm->arch.arm_pmu); + return kvm_pmu_is_partitioned(vcpu->kvm->arch.arm_pmu) && + !kvm_pmu_regs_host_owned(vcpu); }
/** @@ -69,6 +70,7 @@ bool kvm_vcpu_pmu_use_fgt(struct kvm_vcpu *vcpu) u8 hpmn = vcpu->kvm->arch.nr_pmu_counters;
return kvm_vcpu_pmu_is_partitioned(vcpu) && + kvm_pmu_regs_guest_owned(vcpu) && cpus_have_final_cap(ARM64_HAS_FGT) && (hpmn != 0 || cpus_have_final_cap(ARM64_HAS_HPMN0)); } diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c index 1e5f46c1346c..db11a3e9c4b7 100644 --- a/arch/arm64/kvm/pmu.c +++ b/arch/arm64/kvm/pmu.c @@ -496,6 +496,7 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu) init_irq_work(&vcpu->arch.pmu.overflow_work, kvm_pmu_perf_overflow_notify_vcpu);
+ vcpu->arch.pmu.owner = VCPU_REGISTER_HOST_OWNED; vcpu->arch.pmu.created = true; return 0; } @@ -906,3 +907,26 @@ bool pmu_access_el0_disabled(struct kvm_vcpu *vcpu) { return check_pmu_access_disabled(vcpu, ARMV8_PMU_USERENR_EN); } + +bool kvm_pmu_regs_free(struct kvm_vcpu *vcpu) +{ + return vcpu->arch.pmu.owner == VCPU_REGISTER_FREE; +} + +bool kvm_pmu_regs_host_owned(struct kvm_vcpu *vcpu) +{ + return vcpu->arch.pmu.owner == VCPU_REGISTER_HOST_OWNED; +} + +bool kvm_pmu_regs_guest_owned(struct kvm_vcpu *vcpu) +{ + return vcpu->arch.pmu.owner == VCPU_REGISTER_GUEST_OWNED; +} + +void kvm_pmu_regs_set_guest_owned(struct kvm_vcpu *vcpu) +{ + if (kvm_pmu_regs_free(vcpu)) { + vcpu->arch.pmu.owner = VCPU_REGISTER_GUEST_OWNED; + kvm_arm_setup_mdcr_el2(vcpu); + } +} diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index e3d4ca167881..7d4b194bfa0a 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -860,6 +860,8 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p, { u64 val;
+ kvm_pmu_regs_set_guest_owned(vcpu); + if (pmu_access_el0_disabled(vcpu)) return false;
@@ -887,6 +889,8 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p, static bool access_pmselr(struct kvm_vcpu *vcpu, struct sys_reg_params *p, const struct sys_reg_desc *r) { + kvm_pmu_regs_set_guest_owned(vcpu); + if (pmu_access_event_counter_el0_disabled(vcpu)) return false;
@@ -905,6 +909,8 @@ static bool access_pmceid(struct kvm_vcpu *vcpu, struct sys_reg_params *p, { u64 pmceid, mask, shift;
+ kvm_pmu_regs_set_guest_owned(vcpu); + BUG_ON(p->is_write);
if (pmu_access_el0_disabled(vcpu)) @@ -973,6 +979,8 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu, { u64 idx = ~0UL;
+ kvm_pmu_regs_set_guest_owned(vcpu); + if (r->CRn == 9 && r->CRm == 13) { if (r->Op2 == 2) { /* PMXEVCNTR_EL0 */ @@ -1049,6 +1057,8 @@ static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p, { u64 idx, reg, pmselr;
+ kvm_pmu_regs_set_guest_owned(vcpu); + if (pmu_access_el0_disabled(vcpu)) return false;
@@ -1110,6 +1120,8 @@ static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p, { u64 val, mask;
+ kvm_pmu_regs_set_guest_owned(vcpu); + if (pmu_access_el0_disabled(vcpu)) return false;
@@ -1134,7 +1146,10 @@ static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p, static bool access_pminten(struct kvm_vcpu *vcpu, struct sys_reg_params *p, const struct sys_reg_desc *r) { - u64 mask = kvm_pmu_accessible_counter_mask(vcpu); + u64 mask; + + kvm_pmu_regs_set_guest_owned(vcpu); + mask = kvm_pmu_accessible_counter_mask(vcpu);
if (check_pmu_access_disabled(vcpu, 0)) return false; @@ -1171,7 +1186,10 @@ static void writethrough_pmovs(struct kvm_vcpu *vcpu, struct sys_reg_params *p, static bool access_pmovs(struct kvm_vcpu *vcpu, struct sys_reg_params *p, const struct sys_reg_desc *r) { - u64 mask = kvm_pmu_accessible_counter_mask(vcpu); + u64 mask; + + kvm_pmu_regs_set_guest_owned(vcpu); + mask = kvm_pmu_accessible_counter_mask(vcpu);
if (pmu_access_el0_disabled(vcpu)) return false; @@ -1211,6 +1229,8 @@ static bool access_pmswinc(struct kvm_vcpu *vcpu, struct sys_reg_params *p, static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p, const struct sys_reg_desc *r) { + kvm_pmu_regs_set_guest_owned(vcpu); + if (p->is_write) { if (!vcpu_mode_priv(vcpu)) return undef_access(vcpu, p, r);