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Date: Thu, 4 Apr 2024 13:57:36 +0200
From: Andrew Jones <ajones@ventanamicro.com>
To: Atish Patra <atishp@rivosinc.com>
Cc: linux-kernel@vger.kernel.org, Ajay Kaher <akaher@vmware.com>, 
	Alexandre Ghiti <alexghiti@rivosinc.com>, Alexey Makhalov <amakhalov@vmware.com>, 
	Anup Patel <anup@brainfault.org>, 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, 
	VMware PV-Drivers Reviewers <pv-drivers@vmware.com>, Will Deacon <will@kernel.org>, x86@kernel.org
Subject: Re: [PATCH v5 08/22] RISC-V: KVM: Fix the initial sample period value
Message-ID: <20240404-1c3dc9b63f80fc451d3a732a@orel>
References: <20240403080452.1007601-1-atishp@rivosinc.com>
 <20240403080452.1007601-9-atishp@rivosinc.com>
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In-Reply-To: <20240403080452.1007601-9-atishp@rivosinc.com>

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 <atishp@rivosinc.com>
> ---
>  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 <ajones@ventanamicro.com>