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

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Le 15/12/2022 à 20:46, Christophe JAILLET a écrit :
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?

Read kmalloc_array()


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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