[v2] KVM: arm/arm64: Introduce kvm_pmu_vcpu_init() to setup PMU counter idx
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Message ID 1563437710-30756-1-git-send-email-yuzenghui@huawei.com
State New
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  • [v2] KVM: arm/arm64: Introduce kvm_pmu_vcpu_init() to setup PMU counter idx
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Commit Message

Zenghui Yu July 18, 2019, 8:15 a.m. UTC
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 <andrew.murray@arm.com>
Suggested-by: Julien Thierry <julien.thierry@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
---

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(-)

Comments

Julien Thierry July 23, 2019, 8:17 a.m. UTC | #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 <andrew.murray@arm.com>
> Suggested-by: Julien Thierry <julien.thierry@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> ---
> 
> 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 <julien.thierry@arm.com>

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);
>  }
>
Marc Zyngier July 23, 2019, 8:26 a.m. UTC | #2
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 <andrew.murray@arm.com>
>> Suggested-by: Julien Thierry <julien.thierry@arm.com>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
>> ---
>>
>> 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 <julien.thierry@arm.com>

Applied, thanks both.

         M.

Patch
diff mbox series

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);
 }