[PATCH 1/4] perf: nvidia_t410_cmem_latency: fix cpuhp state leak on init failure

[PATCH 1/4] perf: nvidia_t410_cmem_latency: fix cpuhp state leak on init failure

[Saurav Sachidanand]

If platform_driver_register() fails, the cpuhp multi-state registered
by cpuhp_setup_state_multi() is never cleaned up. Add
cpuhp_remove_multi_state() on the error path, mirroring the cleanup
in cmem_lat_pmu_exit().

Fixes: 429b7638b2df ("perf: add NVIDIA Tegra410 CPU Memory Latency PMU")
Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
---
 drivers/perf/nvidia_t410_cmem_latency_pmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/nvidia_t410_cmem_latency_pmu.c b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
index acb8f5571522c..e27bf31b2b366 100644
--- a/drivers/perf/nvidia_t410_cmem_latency_pmu.c
+++ b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
@@ -719,7 +719,11 @@ static int __init cmem_lat_pmu_init(void)
 
 	cmem_lat_pmu_cpuhp_state = ret;
 
-	return platform_driver_register(&cmem_lat_pmu_driver);
+	ret = platform_driver_register(&cmem_lat_pmu_driver);
+	if (ret)
+		cpuhp_remove_multi_state(cmem_lat_pmu_cpuhp_state);
+
+	return ret;
 }
 
 static void __exit cmem_lat_pmu_exit(void)
-- 
2.47.3

[PATCH 2/4] perf: nvidia_t410_cmem_latency: handle PERF_EF_UPDATE in stop

[Saurav Sachidanand]

cmem_lat_pmu_stop() does not read the final counter value when called
with PERF_EF_UPDATE. When perf core calls pmu->del() -> pmu->stop()
with PERF_EF_UPDATE, the last counter delta is lost because the event
is marked stopped without reading hardware.

Add the standard PMU stop pattern: bail out if already stopped, call
the event update function when PERF_EF_UPDATE is requested, then mark
the event stopped.

Fixes: 429b7638b2df ("perf: add NVIDIA Tegra410 CPU Memory Latency PMU")
Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
---
 drivers/perf/nvidia_t410_cmem_latency_pmu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/perf/nvidia_t410_cmem_latency_pmu.c b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
index e27bf31b2b366..c7fa54c7a7c9e 100644
--- a/drivers/perf/nvidia_t410_cmem_latency_pmu.c
+++ b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
@@ -303,6 +303,12 @@ static void cmem_lat_pmu_start(struct perf_event *event, int pmu_flags)
 
 static void cmem_lat_pmu_stop(struct perf_event *event, int pmu_flags)
 {
+	if (event->hw.state & PERF_HES_STOPPED)
+		return;
+
+	if (pmu_flags & PERF_EF_UPDATE)
+		cmem_lat_pmu_event_update(event);
+
 	event->hw.state |= PERF_HES_STOPPED;
 }
 
-- 
2.47.3

[PATCH 3/4] perf: nvidia_t410_c2c: fix cpuhp state leak on init failure

[Saurav Sachidanand]

If platform_driver_register() fails, the cpuhp multi-state registered
by cpuhp_setup_state_multi() is never cleaned up. Add
cpuhp_remove_multi_state() on the error path, mirroring the cleanup
in nv_c2c_pmu_exit().

Fixes: 2f89b7f78c50 ("perf: add NVIDIA Tegra410 C2C PMU")
Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
---
 drivers/perf/nvidia_t410_c2c_pmu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/nvidia_t410_c2c_pmu.c b/drivers/perf/nvidia_t410_c2c_pmu.c
index 411987153ff3f..662fa1bc833a5 100644
--- a/drivers/perf/nvidia_t410_c2c_pmu.c
+++ b/drivers/perf/nvidia_t410_c2c_pmu.c
@@ -1034,7 +1034,12 @@ static int __init nv_c2c_pmu_init(void)
 		return ret;
 
 	nv_c2c_pmu_cpuhp_state = ret;
-	return platform_driver_register(&nv_c2c_pmu_driver);
+
+	ret = platform_driver_register(&nv_c2c_pmu_driver);
+	if (ret)
+		cpuhp_remove_multi_state(nv_c2c_pmu_cpuhp_state);
+
+	return ret;
 }
 
 static void __exit nv_c2c_pmu_exit(void)
-- 
2.47.3

[PATCH 4/4] perf: nvidia_t410_c2c: handle PERF_EF_UPDATE in stop

[Saurav Sachidanand]

nv_c2c_pmu_stop() does not read the final counter value when called
with PERF_EF_UPDATE. The last counter delta is lost when perf core
removes the event.

Add the standard PMU stop pattern: bail out if already stopped, call
nv_c2c_pmu_event_update() when PERF_EF_UPDATE is requested, then mark
the event stopped.

Fixes: 2f89b7f78c50 ("perf: add NVIDIA Tegra410 C2C PMU")
Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
---
 drivers/perf/nvidia_t410_c2c_pmu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/perf/nvidia_t410_c2c_pmu.c b/drivers/perf/nvidia_t410_c2c_pmu.c
index 662fa1bc833a5..39d0e661e4c5c 100644
--- a/drivers/perf/nvidia_t410_c2c_pmu.c
+++ b/drivers/perf/nvidia_t410_c2c_pmu.c
@@ -394,6 +394,12 @@ static void nv_c2c_pmu_start(struct perf_event *event, int pmu_flags)
 
 static void nv_c2c_pmu_stop(struct perf_event *event, int pmu_flags)
 {
+	if (event->hw.state & PERF_HES_STOPPED)
+		return;
+
+	if (pmu_flags & PERF_EF_UPDATE)
+		nv_c2c_pmu_event_update(event);
+
 	event->hw.state |= PERF_HES_STOPPED;
 }
 
-- 
2.47.3

RE: [PATCH 1/4] perf: nvidia_t410_cmem_latency: fix cpuhp state leak on init failure

[Besar Wicaksono]

> -----Original Message-----
> From: Saurav Sachidanand <sauravsc@amazon.com>
> Sent: Wednesday, May 13, 2026 8:06 PM
> To: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>; Besar Wicaksono
> <bwicaksono@nvidia.com>; Ilkka Koskinen
> <ilkka@os.amperecomputing.com>; Andi Shyti <andi.shyti@kernel.org>; linux-
> arm-kernel@lists.infradead.org; linux-perf-users@vger.kernel.org; linux-
> kernel@vger.kernel.org; aghayev@amazon.com; juew@amazon.com; Saurav
> Sachidanand <sauravsc@amazon.com>
> Subject: [PATCH 1/4] perf: nvidia_t410_cmem_latency: fix cpuhp state leak on
> init failure
> 
> External email: Use caution opening links or attachments
> 
> 
> If platform_driver_register() fails, the cpuhp multi-state registered
> by cpuhp_setup_state_multi() is never cleaned up. Add
> cpuhp_remove_multi_state() on the error path, mirroring the cleanup
> in cmem_lat_pmu_exit().
> 
> Fixes: 429b7638b2df ("perf: add NVIDIA Tegra410 CPU Memory Latency
> PMU")
> Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
> ---
>  drivers/perf/nvidia_t410_cmem_latency_pmu.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> index acb8f5571522c..e27bf31b2b366 100644
> --- a/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> +++ b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> @@ -719,7 +719,11 @@ static int __init cmem_lat_pmu_init(void)
> 
>         cmem_lat_pmu_cpuhp_state = ret;
> 
> -       return platform_driver_register(&cmem_lat_pmu_driver);
> +       ret = platform_driver_register(&cmem_lat_pmu_driver);
> +       if (ret)
> +               cpuhp_remove_multi_state(cmem_lat_pmu_cpuhp_state);
> +
> +       return ret;
>  }
> 
>  static void __exit cmem_lat_pmu_exit(void)
> --
> 2.47.3

Reviewed-by: Besar Wicaksono <bwicaksono@nvidia.com>

RE: [PATCH 3/4] perf: nvidia_t410_c2c: fix cpuhp state leak on init failure

[Besar Wicaksono]

> -----Original Message-----
> From: Saurav Sachidanand <sauravsc@amazon.com>
> Sent: Wednesday, May 13, 2026 8:06 PM
> To: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>; Besar Wicaksono
> <bwicaksono@nvidia.com>; Ilkka Koskinen
> <ilkka@os.amperecomputing.com>; Andi Shyti <andi.shyti@kernel.org>; linux-
> arm-kernel@lists.infradead.org; linux-perf-users@vger.kernel.org; linux-
> kernel@vger.kernel.org; aghayev@amazon.com; juew@amazon.com; Saurav
> Sachidanand <sauravsc@amazon.com>
> Subject: [PATCH 3/4] perf: nvidia_t410_c2c: fix cpuhp state leak on init failure
> 
> External email: Use caution opening links or attachments
> 
> 
> If platform_driver_register() fails, the cpuhp multi-state registered
> by cpuhp_setup_state_multi() is never cleaned up. Add
> cpuhp_remove_multi_state() on the error path, mirroring the cleanup
> in nv_c2c_pmu_exit().
> 
> Fixes: 2f89b7f78c50 ("perf: add NVIDIA Tegra410 C2C PMU")
> Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
> ---
>  drivers/perf/nvidia_t410_c2c_pmu.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/nvidia_t410_c2c_pmu.c
> b/drivers/perf/nvidia_t410_c2c_pmu.c
> index 411987153ff3f..662fa1bc833a5 100644
> --- a/drivers/perf/nvidia_t410_c2c_pmu.c
> +++ b/drivers/perf/nvidia_t410_c2c_pmu.c
> @@ -1034,7 +1034,12 @@ static int __init nv_c2c_pmu_init(void)
>                 return ret;
> 
>         nv_c2c_pmu_cpuhp_state = ret;
> -       return platform_driver_register(&nv_c2c_pmu_driver);
> +
> +       ret = platform_driver_register(&nv_c2c_pmu_driver);
> +       if (ret)
> +               cpuhp_remove_multi_state(nv_c2c_pmu_cpuhp_state);
> +
> +       return ret;
>  }
> 
>  static void __exit nv_c2c_pmu_exit(void)
> --
> 2.47.3

Reviewed-by: Besar Wicaksono <bwicaksono@nvidia.com>

RE: [PATCH 2/4] perf: nvidia_t410_cmem_latency: handle PERF_EF_UPDATE in stop

[Besar Wicaksono]

> -----Original Message-----
> From: Saurav Sachidanand <sauravsc@amazon.com>
> Sent: Wednesday, May 13, 2026 8:06 PM
> To: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>; Besar Wicaksono
> <bwicaksono@nvidia.com>; Ilkka Koskinen
> <ilkka@os.amperecomputing.com>; Andi Shyti <andi.shyti@kernel.org>; linux-
> arm-kernel@lists.infradead.org; linux-perf-users@vger.kernel.org; linux-
> kernel@vger.kernel.org; aghayev@amazon.com; juew@amazon.com; Saurav
> Sachidanand <sauravsc@amazon.com>
> Subject: [PATCH 2/4] perf: nvidia_t410_cmem_latency: handle
> PERF_EF_UPDATE in stop
> 
> External email: Use caution opening links or attachments
> 
> 
> cmem_lat_pmu_stop() does not read the final counter value when called
> with PERF_EF_UPDATE. When perf core calls pmu->del() -> pmu->stop()
> with PERF_EF_UPDATE, the last counter delta is lost because the event
> is marked stopped without reading hardware.
> 
> Add the standard PMU stop pattern: bail out if already stopped, call
> the event update function when PERF_EF_UPDATE is requested, then mark
> the event stopped.
> 
> Fixes: 429b7638b2df ("perf: add NVIDIA Tegra410 CPU Memory Latency
> PMU")
> Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
> ---
>  drivers/perf/nvidia_t410_cmem_latency_pmu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> index e27bf31b2b366..c7fa54c7a7c9e 100644
> --- a/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> +++ b/drivers/perf/nvidia_t410_cmem_latency_pmu.c
> @@ -303,6 +303,12 @@ static void cmem_lat_pmu_start(struct perf_event
> *event, int pmu_flags)
> 
>  static void cmem_lat_pmu_stop(struct perf_event *event, int pmu_flags)
>  {
> +       if (event->hw.state & PERF_HES_STOPPED)
> +               return;
> +
> +       if (pmu_flags & PERF_EF_UPDATE)
> +               cmem_lat_pmu_event_update(event);
> +

Hi Saurav,

This call is not needed since the driver called it on pmu_disable callback.
Adding it on stop callback would be redundant.

Regards,
Besar

RE: [PATCH 4/4] perf: nvidia_t410_c2c: handle PERF_EF_UPDATE in stop

[Besar Wicaksono]

> -----Original Message-----
> From: Saurav Sachidanand <sauravsc@amazon.com>
> Sent: Wednesday, May 13, 2026 8:06 PM
> To: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>; Besar Wicaksono
> <bwicaksono@nvidia.com>; Ilkka Koskinen
> <ilkka@os.amperecomputing.com>; Andi Shyti <andi.shyti@kernel.org>; linux-
> arm-kernel@lists.infradead.org; linux-perf-users@vger.kernel.org; linux-
> kernel@vger.kernel.org; aghayev@amazon.com; juew@amazon.com; Saurav
> Sachidanand <sauravsc@amazon.com>
> Subject: [PATCH 4/4] perf: nvidia_t410_c2c: handle PERF_EF_UPDATE in stop
> 
> External email: Use caution opening links or attachments
> 
> 
> nv_c2c_pmu_stop() does not read the final counter value when called
> with PERF_EF_UPDATE. The last counter delta is lost when perf core
> removes the event.
> 
> Add the standard PMU stop pattern: bail out if already stopped, call
> nv_c2c_pmu_event_update() when PERF_EF_UPDATE is requested, then mark
> the event stopped.
> 
> Fixes: 2f89b7f78c50 ("perf: add NVIDIA Tegra410 C2C PMU")
> Signed-off-by: Saurav Sachidanand <sauravsc@amazon.com>
> ---
>  drivers/perf/nvidia_t410_c2c_pmu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/perf/nvidia_t410_c2c_pmu.c
> b/drivers/perf/nvidia_t410_c2c_pmu.c
> index 662fa1bc833a5..39d0e661e4c5c 100644
> --- a/drivers/perf/nvidia_t410_c2c_pmu.c
> +++ b/drivers/perf/nvidia_t410_c2c_pmu.c
> @@ -394,6 +394,12 @@ static void nv_c2c_pmu_start(struct perf_event
> *event, int pmu_flags)
> 
>  static void nv_c2c_pmu_stop(struct perf_event *event, int pmu_flags)
>  {
> +       if (event->hw.state & PERF_HES_STOPPED)
> +               return;
> +
> +       if (pmu_flags & PERF_EF_UPDATE)
> +               nv_c2c_pmu_event_update(event);
> +

Hi Saurav,

This call is not needed since the driver called it on pmu_disable callback.
Adding it on stop callback would be redundant.

Regards,
Besar