We use "pmc->idx" and the "chained" bitmap to determine if the pmc is
chained, in kvm_pmu_pmc_is_chained(). But idx might be uninitialized
(and random) when we doing this decision, through a KVM_ARM_VCPU_INIT
ioctl -> kvm_pmu_vcpu_reset(). And the test_bit() against this random
idx will potentially hit a KASAN BUG [1].
In general, idx is the static property of a PMU counter that is not
expected to be modified across resets, as suggested by Julien. It
looks more reasonable if we can setup the PMU counter idx for a vcpu
in its creation time. Introduce a new function - kvm_pmu_vcpu_init()
for this basic setup. Oh, and the KASAN BUG will get fixed this way.
[1] https://www.spinics.net/lists/kvm-arm/msg36700.html
Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters")
Suggested-by: Andrew Murray <[email protected]>
Suggested-by: Julien Thierry <[email protected]>
Cc: Marc Zyngier <[email protected]>
Signed-off-by: Zenghui Yu <[email protected]>
---
Changes since v1:
- Introduce kvm_pmu_vcpu_init() in vcpu's creation time, move the
assignment of pmc->idx into it.
- Thus change the subject. The old one is "KVM: arm/arm64: Assign
pmc->idx before kvm_pmu_stop_counter()".
Julien, I haven't collected your Acked-by into this version. If you're
still happy with the change, please Ack again. Thanks!
include/kvm/arm_pmu.h | 2 ++
virt/kvm/arm/arm.c | 2 ++
virt/kvm/arm/pmu.c | 18 +++++++++++++++---
3 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 16c769a..6db0304 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -34,6 +34,7 @@ struct kvm_pmu {
u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu);
+void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu);
void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu);
void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val);
@@ -71,6 +72,7 @@ static inline u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
{
return 0;
}
+static inline void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) {}
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_mask(struct kvm_vcpu *vcpu, u64 val) {}
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index f645c0f..c704fa6 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -340,6 +340,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
/* Set up the timer */
kvm_timer_vcpu_init(vcpu);
+ kvm_pmu_vcpu_init(vcpu);
+
kvm_arm_reset_debug_ptr(vcpu);
return kvm_vgic_vcpu_init(vcpu);
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 3dd8238..362a018 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -215,6 +215,20 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
}
/**
+ * kvm_pmu_vcpu_init - assign pmu counter idx for cpu
+ * @vcpu: The vcpu pointer
+ *
+ */
+void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu)
+{
+ int i;
+ struct kvm_pmu *pmu = &vcpu->arch.pmu;
+
+ for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
+ pmu->pmc[i].idx = i;
+}
+
+/**
* kvm_pmu_vcpu_reset - reset pmu state for cpu
* @vcpu: The vcpu pointer
*
@@ -224,10 +238,8 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu)
int i;
struct kvm_pmu *pmu = &vcpu->arch.pmu;
- for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
+ for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]);
- pmu->pmc[i].idx = i;
- }
bitmap_zero(vcpu->arch.pmu.chained, ARMV8_PMU_MAX_COUNTER_PAIRS);
}
--
1.8.3.1
Hi Zenghui,
On 18/07/2019 09:15, Zenghui Yu wrote:
> We use "pmc->idx" and the "chained" bitmap to determine if the pmc is
> chained, in kvm_pmu_pmc_is_chained(). But idx might be uninitialized
> (and random) when we doing this decision, through a KVM_ARM_VCPU_INIT
> ioctl -> kvm_pmu_vcpu_reset(). And the test_bit() against this random
> idx will potentially hit a KASAN BUG [1].
>
> In general, idx is the static property of a PMU counter that is not
> expected to be modified across resets, as suggested by Julien. It
> looks more reasonable if we can setup the PMU counter idx for a vcpu
> in its creation time. Introduce a new function - kvm_pmu_vcpu_init()
> for this basic setup. Oh, and the KASAN BUG will get fixed this way.
>
> [1] https://www.spinics.net/lists/kvm-arm/msg36700.html
>
> Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters")
> Suggested-by: Andrew Murray <[email protected]>
> Suggested-by: Julien Thierry <[email protected]>
> Cc: Marc Zyngier <[email protected]>
> Signed-off-by: Zenghui Yu <[email protected]>
> ---
>
> Changes since v1:
> - Introduce kvm_pmu_vcpu_init() in vcpu's creation time, move the
> assignment of pmc->idx into it.
> - Thus change the subject. The old one is "KVM: arm/arm64: Assign
> pmc->idx before kvm_pmu_stop_counter()".
>
> Julien, I haven't collected your Acked-by into this version. If you're
> still happy with the change, please Ack again. Thanks!
>
Thanks for making the change. This looks good to me:
Acked-by: Julien Thierry <[email protected]>
Thanks,
Julien
> include/kvm/arm_pmu.h | 2 ++
> virt/kvm/arm/arm.c | 2 ++
> virt/kvm/arm/pmu.c | 18 +++++++++++++++---
> 3 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 16c769a..6db0304 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -34,6 +34,7 @@ struct kvm_pmu {
> u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
> void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
> u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu);
> +void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu);
> void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu);
> void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
> void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val);
> @@ -71,6 +72,7 @@ static inline u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
> {
> return 0;
> }
> +static inline void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) {}
> 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_mask(struct kvm_vcpu *vcpu, u64 val) {}
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index f645c0f..c704fa6 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -340,6 +340,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
> /* Set up the timer */
> kvm_timer_vcpu_init(vcpu);
>
> + kvm_pmu_vcpu_init(vcpu);
> +
> kvm_arm_reset_debug_ptr(vcpu);
>
> return kvm_vgic_vcpu_init(vcpu);
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 3dd8238..362a018 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -215,6 +215,20 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
> }
>
> /**
> + * kvm_pmu_vcpu_init - assign pmu counter idx for cpu
> + * @vcpu: The vcpu pointer
> + *
> + */
> +void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu)
> +{
> + int i;
> + struct kvm_pmu *pmu = &vcpu->arch.pmu;
> +
> + for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
> + pmu->pmc[i].idx = i;
> +}
> +
> +/**
> * kvm_pmu_vcpu_reset - reset pmu state for cpu
> * @vcpu: The vcpu pointer
> *
> @@ -224,10 +238,8 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu)
> int i;
> struct kvm_pmu *pmu = &vcpu->arch.pmu;
>
> - for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
> + for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
> kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]);
> - pmu->pmc[i].idx = i;
> - }
>
> bitmap_zero(vcpu->arch.pmu.chained, ARMV8_PMU_MAX_COUNTER_PAIRS);
> }
>
--
Julien Thierry
On 2019-07-23 09:17, Julien Thierry wrote:
> Hi Zenghui,
>
> On 18/07/2019 09:15, Zenghui Yu wrote:
>> We use "pmc->idx" and the "chained" bitmap to determine if the pmc
>> is
>> chained, in kvm_pmu_pmc_is_chained(). But idx might be
>> uninitialized
>> (and random) when we doing this decision, through a
>> KVM_ARM_VCPU_INIT
>> ioctl -> kvm_pmu_vcpu_reset(). And the test_bit() against this
>> random
>> idx will potentially hit a KASAN BUG [1].
>>
>> In general, idx is the static property of a PMU counter that is not
>> expected to be modified across resets, as suggested by Julien. It
>> looks more reasonable if we can setup the PMU counter idx for a vcpu
>> in its creation time. Introduce a new function - kvm_pmu_vcpu_init()
>> for this basic setup. Oh, and the KASAN BUG will get fixed this way.
>>
>> [1] https://www.spinics.net/lists/kvm-arm/msg36700.html
>>
>> Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters")
>> Suggested-by: Andrew Murray <[email protected]>
>> Suggested-by: Julien Thierry <[email protected]>
>> Cc: Marc Zyngier <[email protected]>
>> Signed-off-by: Zenghui Yu <[email protected]>
>> ---
>>
>> Changes since v1:
>> - Introduce kvm_pmu_vcpu_init() in vcpu's creation time, move the
>> assignment of pmc->idx into it.
>> - Thus change the subject. The old one is "KVM: arm/arm64: Assign
>> pmc->idx before kvm_pmu_stop_counter()".
>>
>> Julien, I haven't collected your Acked-by into this version. If
>> you're
>> still happy with the change, please Ack again. Thanks!
>>
>
> Thanks for making the change. This looks good to me:
>
> Acked-by: Julien Thierry <[email protected]>
Applied, thanks both.
M.
--
Jazz is not dead. It just smells funny...