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

[Marion & Christophe JAILLET]

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)