linux-kernel - Re: [v2 06/10] RISC-V: KVM: No need to update the counter value during reset

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Date: Sat, 30 Dec 2023 13:30:17 +0530
From: Anup Patel <anup@...infault.org>
To: Atish Patra <atishp@...osinc.com>
Cc: linux-kernel@...r.kernel.org, Albert Ou <aou@...s.berkeley.edu>, 
	Alexandre Ghiti <alexghiti@...osinc.com>, Andrew Jones <ajones@...tanamicro.com>, 
	Atish Patra <atishp@...shpatra.org>, Conor Dooley <conor.dooley@...rochip.com>, 
	Guo Ren <guoren@...nel.org>, Heiko Stuebner <heiko@...ech.de>, kvm-riscv@...ts.infradead.org, 
	kvm@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	Mark Rutland <mark.rutland@....com>, Palmer Dabbelt <palmer@...belt.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Will Deacon <will@...nel.org>
Subject: Re: [v2 06/10] RISC-V: KVM: No need to update the counter value
 during reset

On Sat, Dec 30, 2023 at 3:20 AM Atish Patra <atishp@...osinc.com> wrote:
>
> The virtual counter value is updated during pmu_ctr_read. There is no need
> to update it in reset case. Otherwise, it will be counted twice which is
> incorrect.
>
> Fixes: 0cb74b65d2e5 ("RISC-V: KVM: Implement perf support without sampling")
> Signed-off-by: Atish Patra <atishp@...osinc.com>

LGTM.

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

Regards,
Anup

> ---
>  arch/riscv/kvm/vcpu_pmu.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> index 86391a5061dd..8c44f26e754d 100644
> --- a/arch/riscv/kvm/vcpu_pmu.c
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -432,12 +432,9 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
>                                 sbiret = SBI_ERR_ALREADY_STOPPED;
>                         }
>
> -                       if (flags & SBI_PMU_STOP_FLAG_RESET) {
> -                               /* Relase the counter if this is a reset request */
> -                               pmc->counter_val += perf_event_read_value(pmc->perf_event,
> -                                                                         &enabled, &running);
> +                       if (flags & SBI_PMU_STOP_FLAG_RESET)
> +                               /* Release the counter if this is a reset request */
>                                 kvm_pmu_release_perf_event(pmc);
> -                       }
>                 } else {
>                         sbiret = SBI_ERR_INVALID_PARAM;
>                 }
> --
> 2.34.1
>