Currently, with VHE, KVM sets ER, CR, SW and EN bits of
PMUSERENR_EL0 to 1 on vcpu_load(), and saves and restores
the register value for the host on vcpu_load() and vcpu_put().
If the value of those bits are cleared on a pCPU with a vCPU
loaded (armv8pmu_start() would do that when PMU counters are
programmed for the guest), PMU access from the guest EL0 might
be trapped to the guest EL1 directly regardless of the current
PMUSERENR_EL0 value of the vCPU.
Fix this by not letting armv8pmu_start() overwrite PMUSERENR_EL0
on the pCPU where PMUSERENR_EL0 for the guest is loaded, and
instead updating the saved shadow register value for the host
so that the value can be restored on vcpu_put() later.
While vcpu_{put,load}() are manipulating PMUSERENR_EL0, disable
IRQs to prevent a race condition between these processes and IPIs
that attempt to update PMUSERENR_EL0 for the host EL0.
Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Suggested-by: Marc Zyngier <maz@xxxxxxxxxx>
Fixes: 83a7a4d643d3 ("arm64: perf: Enable PMU counter userspace access for perf event")
Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
---
arch/arm/include/asm/arm_pmuv3.h | 5 +++++
arch/arm64/include/asm/kvm_host.h | 7 +++++++
arch/arm64/kvm/hyp/include/hyp/switch.h | 2 ++
arch/arm64/kvm/hyp/vhe/switch.c | 14 +++++++++++++
arch/arm64/kvm/pmu.c | 27 +++++++++++++++++++++++++
drivers/perf/arm_pmuv3.c | 21 ++++++++++++++++---
6 files changed, 73 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
index f4db3e75d75f..f3cd04ff022d 100644
--- a/arch/arm/include/asm/arm_pmuv3.h
+++ b/arch/arm/include/asm/arm_pmuv3.h
@@ -222,6 +222,11 @@ static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
return false;
}
+static inline bool kvm_set_pmuserenr(u64 val)
+{
+ return false;
+}
+
/* PMU Version in DFR Register */
#define ARMV8_PMU_DFR_VER_NI 0
#define ARMV8_PMU_DFR_VER_V3P4 0x5
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7e7e19ef6993..9787503ff43f 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -699,6 +699,8 @@ struct kvm_vcpu_arch {
#define SYSREGS_ON_CPU __vcpu_single_flag(sflags, BIT(4))
/* Software step state is Active-pending */
#define DBG_SS_ACTIVE_PENDING __vcpu_single_flag(sflags, BIT(5))
+/* PMUSERENR for the guest EL0 is on physical CPU */
+#define PMUSERENR_ON_CPU __vcpu_single_flag(sflags, BIT(6))
/* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
@@ -1065,9 +1067,14 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu);
#ifdef CONFIG_KVM
void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr);
void kvm_clr_pmu_events(u32 clr);
+bool kvm_set_pmuserenr(u64 val);
#else
static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
static inline void kvm_clr_pmu_events(u32 clr) {}
+static inline bool kvm_set_pmuserenr(u64 val)
+{
+ return false;
+}
#endif
void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 51229d847103..c530cf6b4bef 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -89,6 +89,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
ctxt_sys_reg(hctxt, PMUSERENR_EL0) = read_sysreg(pmuserenr_el0);
write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
+ vcpu_set_flag(vcpu, PMUSERENR_ON_CPU);
}
vcpu->arch.mdcr_el2_host = read_sysreg(mdcr_el2);
@@ -116,6 +117,7 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
write_sysreg(ctxt_sys_reg(hctxt, PMUSERENR_EL0), pmuserenr_el0);
+ vcpu_clear_flag(vcpu, PMUSERENR_ON_CPU);
}
if (cpus_have_final_cap(ARM64_SME)) {
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 3d868e84c7a0..3f0b5756c956 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -92,14 +92,28 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
}
NOKPROBE_SYMBOL(__deactivate_traps);
+/*
+ * Disable IRQs in {activate,deactivate}_traps_vhe_{load,put}() to
+ * prevent a race condition between context switching of PMUSERENR_EL0
+ * in __{activate,deactivate}_traps_common() and IPIs that attempts to
+ * update PMUSERENR_EL0. See also kvm_set_pmuserenr().
+ */
void activate_traps_vhe_load(struct kvm_vcpu *vcpu)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
__activate_traps_common(vcpu);
+ local_irq_restore(flags);
}
void deactivate_traps_vhe_put(struct kvm_vcpu *vcpu)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
__deactivate_traps_common(vcpu);
+ local_irq_restore(flags);
}
static const exit_handler_fn hyp_exit_handlers[] = {
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 7887133d15f0..121f1a14c829 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -209,3 +209,30 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu)
kvm_vcpu_pmu_enable_el0(events_host);
kvm_vcpu_pmu_disable_el0(events_guest);
}
+
+/*
+ * With VHE, keep track of the PMUSERENR_EL0 value for the host EL0 on the pCPU
+ * where PMUSERENR_EL0 for the guest is loaded, since PMUSERENR_EL0 is switched
+ * to the value for the guest on vcpu_load(). The value for the host EL0
+ * will be restored on vcpu_put(), before returning to userspace.
+ * This isn't necessary for nVHE, as the register is context switched for
+ * every guest enter/exit.
+ *
+ * Return true if KVM takes care of the register. Otherwise return false.
+ */
+bool kvm_set_pmuserenr(u64 val)
+{
+ struct kvm_cpu_context *hctxt;
+ struct kvm_vcpu *vcpu;
+
+ if (!kvm_arm_support_pmu_v3() || !has_vhe())
+ return false;
+
+ vcpu = kvm_get_running_vcpu();
+ if (!vcpu || !vcpu_get_flag(vcpu, PMUSERENR_ON_CPU))
+ return false;
+
+ hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+ ctxt_sys_reg(hctxt, PMUSERENR_EL0) = val;
+ return true;
+}
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index c98e4039386d..93b7edb5f1e7 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -677,9 +677,25 @@ static inline u32 armv8pmu_getreset_flags(void)
return value;
}
+static void update_pmuserenr(u64 val)
+{
+ lockdep_assert_irqs_disabled();
+
+ /*
+ * The current PMUSERENR_EL0 value might be the value for the guest.
+ * If that's the case, have KVM keep tracking of the register value
+ * for the host EL0 so that KVM can restore it before returning to
+ * the host EL0. Otherwise, update the register now.
+ */
+ if (kvm_set_pmuserenr(val))
+ return;
+
+ write_pmuserenr(val);
+}
+
static void armv8pmu_disable_user_access(void)
{
- write_pmuserenr(0);
+ update_pmuserenr(0);
}
static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu)
@@ -695,8 +711,7 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu)
armv8pmu_write_evcntr(i, 0);
}
- write_pmuserenr(0);
- write_pmuserenr(ARMV8_PMU_USERENR_ER | ARMV8_PMU_USERENR_CR);
+ update_pmuserenr(ARMV8_PMU_USERENR_ER | ARMV8_PMU_USERENR_CR);
}
static void armv8pmu_enable_event(struct perf_event *event)
--
2.41.0.rc0.172.g3f132b7071-goog
