[PULL 2/8] KVM: arm/arm64: PMU: Fix overflow interrupt injection

Christoffer Dall
2017-09-05T14:52:01Z

From: Andrew Jones <drjones@redhat.com>

kvm_pmu_overflow_set() is called from perf's interrupt handler,
making the call of kvm_vgic_inject_irq() from it introduced with
"KVM: arm/arm64: PMU: remove request-less vcpu kick" a really bad
idea, as it's quite easy to try and retake a lock that the
interrupted context is already holding. The fix is to use a vcpu
kick, leaving the interrupt injection to kvm_pmu_sync_hwstate(),
like it was doing before the refactoring. We don't just revert,
though, because before the kick was request-less, leaving the vcpu
exposed to the request-less vcpu kick race, and also because the
kick was used unnecessarily from register access handlers.

Cc: stable@vger.kernel.org
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/kvm/sys_regs.c | 2 +-
include/kvm/arm_pmu.h | 2 --
virt/kvm/arm/pmu.c | 43 +++++++++++++++----------------------------
3 files changed, 16 insertions(+), 31 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 7786288..2e070d3 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -764,7 +764,7 @@ static bool access_pmovs(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (p->is_write) {
if (r->CRm & 0x2)
/* accessing PMOVSSET_EL0 */
- kvm_pmu_overflow_set(vcpu, p->regval & mask);
+ vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= (p->regval & mask);
else
/* accessing PMOVSCLR_EL0 */
vcpu_sys_reg(vcpu, PMOVSSET_EL0) &= ~(p->regval & mask);
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index f6e0306..f87fe20 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -48,7 +48,6 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu);
void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val);
void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val);
-void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val);
void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu);
void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu);
bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu);
@@ -86,7 +85,6 @@ static inline void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val) {}
static inline void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val) {}
-static inline void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val) {}
static inline void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu) {}
static inline bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index fc8a723..8a9c423 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -203,11 +203,15 @@ static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
return reg;
}

-static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)
+static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
{
struct kvm_pmu *pmu = &vcpu->arch.pmu;
- bool overflow = !!kvm_pmu_overflow_status(vcpu);
+ bool overflow;
+
+ if (!kvm_arm_pmu_v3_ready(vcpu))
+ return;

+ overflow = !!kvm_pmu_overflow_status(vcpu);
if (pmu->irq_level == overflow)
return;

@@ -215,33 +219,11 @@ static void kvm_pmu_check_overflow(struct kvm_vcpu *vcpu)

if (likely(irqchip_in_kernel(vcpu->kvm))) {
int ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
- pmu->irq_num, overflow,
- &vcpu->arch.pmu);
+ pmu->irq_num, overflow, pmu);
WARN_ON(ret);
}
}

-/**
- * kvm_pmu_overflow_set - set PMU overflow interrupt
- * @vcpu: The vcpu pointer
- * @val: the value guest writes to PMOVSSET register
- */
-void kvm_pmu_overflow_set(struct kvm_vcpu *vcpu, u64 val)
-{
- if (val == 0)
- return;
-
- vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= val;
- kvm_pmu_check_overflow(vcpu);
-}
-
-static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
-{
- if (!kvm_arm_pmu_v3_ready(vcpu))
- return;
- kvm_pmu_check_overflow(vcpu);
-}
-
bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)
{
struct kvm_pmu *pmu = &vcpu->arch.pmu;
@@ -303,7 +285,7 @@ static inline struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
}

/**
- * When perf event overflows, call kvm_pmu_overflow_set to set overflow status.
+ * When the perf event overflows, set the overflow status and inform the vcpu.
*/
static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
struct perf_sample_data *data,
@@ -313,7 +295,12 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
struct kvm_vcpu *vcpu = kvm_pmc_to_vcpu(pmc);
int idx = pmc->idx;

- kvm_pmu_overflow_set(vcpu, BIT(idx));
+ vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(idx);
+
+ if (kvm_pmu_overflow_status(vcpu)) {
+ kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
+ kvm_vcpu_kick(vcpu);
+ }
}

/**
@@ -341,7 +328,7 @@ void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
reg = lower_32_bits(reg);
vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) = reg;
if (!reg)
- kvm_pmu_overflow_set(vcpu, BIT(i));
+ vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(i);
}
}
}
--
2.9.0