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References: <20240420151741.962500-1-atishp@rivosinc.com> <20240420151741.962500-11-atishp@rivosinc.com>
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From: Anup Patel <anup@brainfault.org>
Date: Mon, 22 Apr 2024 10:54:52 +0530
Message-ID: <CAAhSdy34VhGY3v9h3cw167MafKHOF1dL6zqB7Wi6A9Z4fo7ZNg@mail.gmail.com>
Subject: Re: [PATCH v8 10/24] RISC-V: KVM: Fix the initial sample period value
To: Atish Patra <atishp@rivosinc.com>
Cc: linux-kernel@vger.kernel.org, Andrew Jones <ajones@ventanamicro.com>, 
	Ajay Kaher <ajay.kaher@broadcom.com>, Albert Ou <aou@eecs.berkeley.edu>, 
	Alexandre Ghiti <alexghiti@rivosinc.com>, samuel.holland@sifive.com, 
	Conor Dooley <conor.dooley@microchip.com>, Juergen Gross <jgross@suse.com>, 
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, 
	linux-kselftest@vger.kernel.org, linux-riscv@lists.infradead.org, 
	Mark Rutland <mark.rutland@arm.com>, Palmer Dabbelt <palmer@dabbelt.com>, 
	Paolo Bonzini <pbonzini@redhat.com>, Paul Walmsley <paul.walmsley@sifive.com>, 
	Shuah Khan <shuah@kernel.org>, virtualization@lists.linux.dev, 
	Will Deacon <will@kernel.org>, x86@kernel.org
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On Sat, Apr 20, 2024 at 5:18=E2=80=AFAM Atish Patra <atishp@rivosinc.com> w=
rote:
>
> 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 *pm=
c)
>         u64 sample_period;
>
>         if (!pmc->counter_val)
> -               sample_period =3D counter_val_mask + 1;
> +               sample_period =3D counter_val_mask;
>         else
>                 sample_period =3D (-pmc->counter_val) & counter_val_mask;
>
> --
> 2.34.1
>