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

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Message-ID: <24af516c-53db-c4f5-6745-7e3a4a2fdf26@wanadoo.fr>
Date:   Thu, 15 Dec 2022 20:49:03 +0100
From:   Marion & Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     arnd@...nel.org
Cc:     Hawking.Zhang@....com, Jack.Gui@....com, KevinYang.Wang@....com,
        Xinhui.Pan@....com, airlied@...il.com, alexander.deucher@....com,
        amd-gfx@...ts.freedesktop.org, arnd@...db.de,
        christian.koenig@....com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, evan.quan@....com,
        kenneth.feng@....com, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, nathan@...nel.org, ndesaulniers@...gle.com,
        trix@...hat.com
Subject: Re: [PATCH] drm/amd/pm: avoid large variable on kernel stack



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@...lic.gmane.org>
>>
>> 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@...lic.gmane.org>
>> ---
>>   .../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)
> 
>