Re: [PATCH 1/1] perf: RISC-V: Limit the number of counters returned from SBI.

[Andrew Jones]

On Fri, Apr 28, 2023 at 11:02:56AM +0000, Viacheslav Mitrofanov wrote:
> Perf gets the number of supported counters from SBI. If it happens that
> the number of returned counters more than RISCV_MAX_COUNTERS the code
> trusts it. It does not lead to an immediate problem but can potentially
> lead to it. Prevent getting more than RISCV_MAX_COUNTERS from SBI.

I recall suggesting we do this during the KVM PMU review, but I guess we
forgot.

> 
> Signed-off-by: Viacheslav Mitrofanov <v.v.mitrofanov@xxxxxxxxx>
> ---
>  drivers/perf/riscv_pmu_sbi.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> index 70cb50fd41c2..0183bf911bfb 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
> @@ -867,6 +867,11 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
>  		pr_err("SBI PMU extension doesn't provide any counters\n");
>  		goto out_free;
>  	}

Need blank line here

> +	/* It is possible to get from SBI more than max number of counters */
> +	if (num_counters > RISCV_MAX_COUNTERS) {
> +		pr_warn("SBI returned more than maximum number of counters\n");
                                               ^ the

This should be a pr_info.


> +		num_counters = RISCV_MAX_COUNTERS;
> +	}

Otherwise,

Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>

Thanks,
drew