Calling arm_cmn_event_clear() before all DTC indices are allocated is
wrong, and can lead to arm_cmn_event_add() erroneously clearing live
counters from full DTCs where allocation fails. Since the DTC counters
are only updated by arm_cmn_init_counter() after all DTC and DTM
allocations succeed, nothing actually needs cleaning up in this case
anyway, and it should just return directly as it did before.

Fixes: 7633ec2c262f ("perf/arm-cmn: Rework DTC counters (again)")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/perf/arm-cmn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 86d970e74129..c584165b13ba 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1816,7 +1816,7 @@ static int arm_cmn_event_add(struct perf_event *event, int flags)
 			idx = 0;
 			while (cmn->dtc[j].counters[idx])
 				if (++idx == CMN_DT_NUM_COUNTERS)
-					goto free_dtms;
+					return -ENOSPC;
 		}
 		hw->dtc_idx[j] = idx;
 	}
-- 
2.39.2.101.g768bb238c484.dirty

On Mon, 11 Dec 2023 19:27:28 +0000, Robin Murphy wrote:
> Calling arm_cmn_event_clear() before all DTC indices are allocated is
> wrong, and can lead to arm_cmn_event_add() erroneously clearing live
> counters from full DTCs where allocation fails. Since the DTC counters
> are only updated by arm_cmn_init_counter() after all DTC and DTM
> allocations succeed, nothing actually needs cleaning up in this case
> anyway, and it should just return directly as it did before.
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] perf/arm-cmn: Fail DTC counter allocation correctly
      https://git.kernel.org/arm64/c/1892fe103c3a

-- 
Catalin

On Mon, Dec 11, 2023 at 07:27:28PM +0000, Robin Murphy wrote:
> Calling arm_cmn_event_clear() before all DTC indices are allocated is
> wrong, and can lead to arm_cmn_event_add() erroneously clearing live
> counters from full DTCs where allocation fails. Since the DTC counters
> are only updated by arm_cmn_init_counter() after all DTC and DTM
> allocations succeed, nothing actually needs cleaning up in this case
> anyway, and it should just return directly as it did before.
> 
> Fixes: 7633ec2c262f ("perf/arm-cmn: Rework DTC counters (again)")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/perf/arm-cmn.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
> index 86d970e74129..c584165b13ba 100644
> --- a/drivers/perf/arm-cmn.c
> +++ b/drivers/perf/arm-cmn.c
> @@ -1816,7 +1816,7 @@ static int arm_cmn_event_add(struct perf_event *event, int flags)
>  			idx = 0;
>  			while (cmn->dtc[j].counters[idx])
>  				if (++idx == CMN_DT_NUM_COUNTERS)
> -					goto free_dtms;
> +					return -ENOSPC;
>  		}
>  		hw->dtc_idx[j] = idx;
>  	}
> -- 
> 2.39.2.101.g768bb238c484.dirty

Acked-by: Will Deacon <will@kernel.org>

Catalin -- please can you take this one as a fix?

Cheers,

Will

On Mon, 11 Dec 2023, Robin Murphy wrote:
> Calling arm_cmn_event_clear() before all DTC indices are allocated is
> wrong, and can lead to arm_cmn_event_add() erroneously clearing live
> counters from full DTCs where allocation fails. Since the DTC counters
> are only updated by arm_cmn_init_counter() after all DTC and DTM
> allocations succeed, nothing actually needs cleaning up in this case
> anyway, and it should just return directly as it did before.
>
> Fixes: 7633ec2c262f ("perf/arm-cmn: Rework DTC counters (again)")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

That's a good catch.

     Reviewed-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>

Cheers, Ilkka

> ---
> drivers/perf/arm-cmn.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
> index 86d970e74129..c584165b13ba 100644
> --- a/drivers/perf/arm-cmn.c
> +++ b/drivers/perf/arm-cmn.c
> @@ -1816,7 +1816,7 @@ static int arm_cmn_event_add(struct perf_event *event, int flags)
> 			idx = 0;
> 			while (cmn->dtc[j].counters[idx])
> 				if (++idx == CMN_DT_NUM_COUNTERS)
> -					goto free_dtms;
> +					return -ENOSPC;
> 		}
> 		hw->dtc_idx[j] = idx;
> 	}
> -- 
> 2.39.2.101.g768bb238c484.dirty
>
>