[PATCH 1/3] drm/amdgpu: Warn when bad pages approaches 90% threshold

[Felix Kuehling]

On 2021-10-20 12:35 p.m., Kent Russell wrote:
> Currently dmesg doesn't warn when the number of bad pages approaches the
> threshold for page retirement. WARN when the number of bad pages
> is at 90% or greater for easier checks and planning, instead of waiting
> until the GPU is full of bad pages
>
> Cc: Luben Tuikov <luben.tuikov at amd.com>
> Cc: Mukul Joshi <Mukul.Joshi at amd.com>
> Signed-off-by: Kent Russell <kent.russell at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ras_eeprom.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras_eeprom.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras_eeprom.c
> index f4c05ff4b26c..1ede0f0d6f55 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras_eeprom.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras_eeprom.c
> @@ -1071,12 +1071,29 @@ int amdgpu_ras_eeprom_init(struct amdgpu_ras_eeprom_control *control,
>   	control->ras_fri = RAS_OFFSET_TO_INDEX(control, hdr->first_rec_offset);
>   
>   	if (hdr->header == RAS_TABLE_HDR_VAL) {
> +		int threshold = 0;

ras->bad_page_cnt_threshold is uint32_t. I'd recommend using the same 
type. Also add an empty line after the declaration to avoid a checkpatch 
warning.


>   		DRM_DEBUG_DRIVER("Found existing EEPROM table with %d records",
>   				 control->ras_num_recs);
>   		res = __verify_ras_table_checksum(control);
>   		if (res)
>   			DRM_ERROR("RAS table incorrect checksum or error:%d\n",
>   				  res);
> +
> +		/* threshold = 0 means that page retirement is disabled, while
> +		 * threshold = -1 means default behaviour
> +		 */
> +		if (amdgpu_bad_page_threshold == -1)
> +			threshold = ras->bad_page_cnt_threshold;
> +		else if (amdgpu_bad_page_threshold > 0)
> +			threshold = amdgpu_bad_page_threshold;
> +
> +		/* Since multiplcation is transitive, a = 9b/10 is the same
> +		 * as 10a = 9b. Use this for our 90% limit to avoid rounding
> +		 */
> +		if (threshold > 0 && ((control->ras_num_recs * 10) >= (threshold * 9)))

Not sure how big these values can get, but you may need to cast to 
(uint64_t) before the multiplications to avoid overflows. Alternatively 
you could use (control->ras_num_recs / 9 >= threshold / 10). It'll 
round, but never overflow.


> +			DRM_WARN("RAS records:%u exceeds 90%% of threshold:%d",

Nitpick: I'd add space after the two colons for readability. The 
threshold should use %u if you make it uint32_t. This can never be negative.

Regards,
   Felix


> +					control->ras_num_recs,
> +					threshold);
>   	} else if (hdr->header == RAS_TABLE_HDR_BAD &&
>   		   amdgpu_bad_page_threshold != 0) {
>   		res = __verify_ras_table_checksum(control);