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@xxxxxxxxxx>
---
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);
--
2.50.0.727.gbf7dc18ff4-goog
