On Tue, Mar 05, 2024 at 03:52:23PM +0000, Pu Lehui wrote:
> From: Pu Lehui <pulehui@xxxxxxxxxx>
>
> RISC-V perf does not yet support branch sampling. Two riscv bpf
> testcases get_branch_snapshot and perf_branches/perf_branches_hw failed
> due to not disabling such sampling.
>
> Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
This seems worthy of a fixes tag. For what commit I do not know, but I
figure it is a problem currently in mainline and a fix should be
backported?
> ---
> drivers/perf/riscv_pmu.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/perf/riscv_pmu.c b/drivers/perf/riscv_pmu.c
> index c78a6fd6c57f..bc42cb95a97c 100644
> --- a/drivers/perf/riscv_pmu.c
> +++ b/drivers/perf/riscv_pmu.c
> @@ -313,6 +313,10 @@ static int riscv_pmu_event_init(struct perf_event *event)
> u64 event_config = 0;
> uint64_t cmask;
>
> + /* does not support taken branch sampling */
Skimming patchwork, I found this comment confusing.
Isolated from the commit message, which it will be once committed, it
was not immediately clear that you were referring to the driver. I think
it is just matter of making this a complete sentence that starts by
mentioning /what/ does not support this feature. Is it the driver? Does
the spec not allow it? etc
Cheers,
Conor.
> + if (has_branch_stack(event))
> + return -EOPNOTSUPP;
> +
> hwc->flags = 0;
> mapped_event = rvpmu->event_map(event, &event_config);
> if (mapped_event < 0) {
> --
> 2.34.1
>
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