2024-04-03 08:07:43

by Atish Kumar Patra

Subject: [PATCH v5 08/22] RISC-V: KVM: Fix the initial sample period value

The initial sample period value when counter value is not assigned
should be set to maximum value supported by the counter width.
Otherwise, it may result in spurious interrupts.

Signed-off-by: Atish Patra <[email protected]>
---
arch/riscv/kvm/vcpu_pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 86391a5061dd..cee1b9ca4ec4 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -39,7 +39,7 @@ static u64 kvm_pmu_get_sample_period(struct kvm_pmc *pmc)
u64 sample_period;

if (!pmc->counter_val)
- sample_period = counter_val_mask + 1;
+ sample_period = counter_val_mask;
else
sample_period = (-pmc->counter_val) & counter_val_mask;

--
2.34.1

2024-04-04 11:57:52

by Andrew Jones

Subject: Re: [PATCH v5 08/22] RISC-V: KVM: Fix the initial sample period value

On Wed, Apr 03, 2024 at 01:04:37AM -0700, Atish Patra wrote:
> The initial sample period value when counter value is not assigned
> should be set to maximum value supported by the counter width.
> Otherwise, it may result in spurious interrupts.
>
> Signed-off-by: Atish Patra <[email protected]>
> ---
> arch/riscv/kvm/vcpu_pmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> index 86391a5061dd..cee1b9ca4ec4 100644
> --- a/arch/riscv/kvm/vcpu_pmu.c
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -39,7 +39,7 @@ static u64 kvm_pmu_get_sample_period(struct kvm_pmc *pmc)
> u64 sample_period;
>
> if (!pmc->counter_val)
> - sample_period = counter_val_mask + 1;
> + sample_period = counter_val_mask;
> else
> sample_period = (-pmc->counter_val) & counter_val_mask;
>
> --
> 2.34.1
>

Reviewed-by: Andrew Jones <[email protected]>