diff mbox series

[v8,10/24] RISC-V: KVM: Fix the initial sample period value

Message ID 20240420151741.962500-11-atishp@rivosinc.com (mailing list archive)
State New, archived
Headers show
Series RISC-V SBI v2.0 PMU improvements and Perf sampling in KVM guest | expand

Commit Message

Atish Kumar Patra April 20, 2024, 3:17 p.m. UTC
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.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 arch/riscv/kvm/vcpu_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Anup Patel April 22, 2024, 5:24 a.m. UTC | #1
On Sat, Apr 20, 2024 at 5:18 AM Atish Patra <atishp@rivosinc.com> 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.
>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
>  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
>
diff mbox series

Patch

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;