Re: [PATCH] drm/amd/pm: avoid large variable on kernel stack

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Le 15/12/2022 à 17:36, Arnd Bergmann a écrit :
From: Arnd Bergmann <arnd-r2nGTMty4D4@xxxxxxxxxxxxxxxx>

The activity_monitor_external[] array is too big to fit on the
kernel stack, resulting in this warning with clang:

drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu13/smu_v13_0_7_ppt.c:1438:12: error: stack frame size (1040) exceeds limit (1024) in 'smu_v13_0_7_get_power_profile_mode' [-Werror,-Wframe-larger-than]

Use dynamic allocation instead. It should also be possible to
have single element here instead of the array, but this seems
easier.

Fixes: 334682ae8151 ("drm/amd/pm: enable workload type change on smu_v13_0_7")
Signed-off-by: Arnd Bergmann <arnd-r2nGTMty4D4@xxxxxxxxxxxxxxxx>
---
  .../drm/amd/pm/swsmu/smu13/smu_v13_0_7_ppt.c  | 21 ++++++++++++++-----
  1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0_7_ppt.c b/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0_7_ppt.c
index c270f94a1b86..7eba854e09ec 100644
--- a/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0_7_ppt.c
+++ b/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0_7_ppt.c
@@ -1439,7 +1439,7 @@ static int smu_v13_0_7_get_power_limit(struct smu_context *smu,
static int smu_v13_0_7_get_power_profile_mode(struct smu_context *smu, char *buf)
  {
-	DpmActivityMonitorCoeffIntExternal_t activity_monitor_external[PP_SMC_POWER_PROFILE_COUNT];
+	DpmActivityMonitorCoeffIntExternal_t *activity_monitor_external;
  	uint32_t i, j, size = 0;
  	int16_t workload_type = 0;
  	int result = 0;
@@ -1447,6 +1447,12 @@ static int smu_v13_0_7_get_power_profile_mode(struct smu_context *smu, char *buf
  	if (!buf)
  		return -EINVAL;
+ activity_monitor_external = kcalloc(sizeof(activity_monitor_external),

Hi,

Before, 'activity_monitor_external' was not initialized.
Maybe kcalloc() is enough?

sizeof(*activity_monitor_external)?
     ~~~~

+					    PP_SMC_POWER_PROFILE_COUNT,
+					    GFP_KERNEL);
+	if (!activity_monitor_external)
+		return -ENOMEM;
+
  	size += sysfs_emit_at(buf, size, "                              ");
  	for (i = 0; i <= PP_SMC_POWER_PROFILE_WINDOW3D; i++)

Unrelated, but wouldn't it be more straightforward with "< PP_SMC_POWER_PROFILE_COUNT"?

  		size += sysfs_emit_at(buf, size, "%-14s%s", amdgpu_pp_profile_name[i],
@@ -1459,15 +1465,17 @@ static int smu_v13_0_7_get_power_profile_mode(struct smu_context *smu, char *buf
  		workload_type = smu_cmn_to_asic_specific_index(smu,
  							       CMN2ASIC_MAPPING_WORKLOAD,
  							       i);
-		if (workload_type < 0)
-			return -EINVAL;
+		if (workload_type < 0) {
+			result = -EINVAL;
+			goto out;
+		}
result = smu_cmn_update_table(smu,
  					  SMU_TABLE_ACTIVITY_MONITOR_COEFF, workload_type,
  					  (void *)(&activity_monitor_external[i]), false);
  		if (result) {
  			dev_err(smu->adev->dev, "[%s] Failed to get activity monitor!", __func__);
-			return result;
+			goto out;
  		}
  	}
@@ -1495,7 +1503,10 @@ do { \
  	PRINT_DPM_MONITOR(Fclk_BoosterFreq);
  #undef PRINT_DPM_MONITOR
- return size;
+	result = size;
+out:
+	kfree(activity_monitor_external);
+	return result;
  }
static int smu_v13_0_7_set_power_profile_mode(struct smu_context *smu, long *input, uint32_t size)




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