Re: [PATCH 6/6] drm/xe/log: Relax location ID recognition

["Mallesh, Koujalagi" <mallesh.koujalagi@intel.com>]

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On 04-09-2026 10:35 pm, Michal Wajdeczko wrote:
> It turned out that during early probe phase, VFs use detached from
> the xe_device, temporary xe_gt objects, which when used as location
> in xe_log() macros, will be treated by the dmesg decoration code as
> bogus, possibly triggering a WARN, and the output will look like:
>
>   [drm] *ERROR* SIGID=104 (-ETIMEDOUT) LOC3.0? GUC: MMIO request ...
>
> instead of expected:
>
>   [drm] *ERROR* SIGID=104 (-ETIMEDOUT) Tile0: GT0: GUC: MMIO request ...
>
> Relax the tile/GT id validation and instead of looking for the real
> objects, only check if encoded id is within the range of possible
> tiles or GTs on the current xe device, using data from the device
> descriptor rather then the object list.

nit: 'rather than'

Please mention invalid id case, how it's going to render like

Warn + Tile3?  GT9? now.

>
> Fixes: 1151b9f6f465 ("drm/xe/log: Add component/location decorations to dmesg")
> Signed-off-by: Michal Wajdeczko<michal.wajdeczko@intel.com>
> ---
> Cc: Rodrigo Vivi<rodrigo.vivi@intel.com>
> Cc: Mallesh Koujalagi<mallesh.koujalagi@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_log.c | 40 ++++++++++++++++++++++++-------------
>   1 file changed, 26 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_log.c b/drivers/gpu/drm/xe/xe_log.c
> index 5549ef6966fd..29eb16db3320 100644
> --- a/drivers/gpu/drm/xe/xe_log.c
> +++ b/drivers/gpu/drm/xe/xe_log.c
> @@ -10,6 +10,7 @@
>   
>   #include "xe_device.h"
>   #include "xe_log.h"
> +#include "xe_pci_types.h"
>   #include "xe_printk.h"
>   
>   static void log_emit_cper(struct pci_dev *pdev, int cper_sev, enum xe_sigid sigid,
> @@ -52,18 +53,24 @@ static const char *log_component_prefix(u32 component)
>   	return component ? log_unknown_component_prefix(component) : "";
>   }
>   
> -static struct xe_gt *get_gt_safe(struct pci_dev *pdev, u8 id)
> +static bool allowed_tile_id(struct xe_device *xe, u8 tile_id)
>   {
> -	struct xe_device *xe = pdev_to_xe_device(pdev);
> +	return tile_id < 1 + xe->desc->max_remote_tiles;
> +}
>   
> -	return xe ? xe_device_get_gt(xe, id) : NULL;
> +static bool allowed_gt_id(struct xe_device *xe, u8 gt_id)
> +{
> +	return gt_id < (1 + xe->desc->max_remote_tiles) * xe->desc->max_gt_per_tile;
>   }
>   
> -static struct xe_tile *get_tile_safe(struct pci_dev *pdev, u8 id)
> +static u8 gt_id_to_tile_id(struct xe_device *xe, u8 gt_id)
>   {
> -	struct xe_device *xe = pdev_to_xe_device(pdev);
> +	return gt_id / xe->desc->max_gt_per_tile;

hmm, we need to check max_gt_per_tile should not be zero to avoid hard 
Oops. I know in real scenario, max_gt_per_tile

value is greater than 0 and less than equal to XE_MAX_GT_PER_TILE, 
however rogue user can write kunit test case and manipulate it, to avoid 
such scenario, we need to handle it.

Thanks,

-/Mallesh

> +}
>   
> -	return xe && id < xe->info.tile_count ? &xe->tiles[id] : NULL;
> +static const char *location_suffix(bool valid)
> +{
> +	return valid ? ":" : "?";
>   }
>   
>   static const char *log_location_prefix(struct pci_dev *pdev, u32 location, char *buf, size_t size)
> @@ -76,17 +83,22 @@ static const char *log_location_prefix(struct pci_dev *pdev, u32 location, char
>   			goto unrecognized;
>   		strscpy(buf, "", size);
>   	} else if (type == XE_LOG_LOCATION_TYPE_TILE) {
> -		struct xe_tile *tile = get_tile_safe(pdev, id);
> +		struct xe_device *xe = xe_any_to_xe(pdev);
> +		bool valid = xe ? allowed_tile_id(xe, id) : false;
> +		const char *pad = location_suffix(valid);
>   
> -		if (!tile)
> -			goto unrecognized;
> -		snprintf(buf, size, "Tile%u: ", id);
> +		pci_WARN(pdev, !valid && IS_ENABLED(CONFIG_DRM_XE_DEBUG),
> +			 "LOG: invalid tile identifier: %u\n", id);
> +		snprintf(buf, size, "Tile%u%s ", id, pad);
>   	} else if (type == XE_LOG_LOCATION_TYPE_GT) {
> -		struct xe_gt *gt = get_gt_safe(pdev, id);
> +		struct xe_device *xe = xe_any_to_xe(pdev);
> +		bool valid = xe ? allowed_gt_id(xe, id) : false;
> +		const char *pad = location_suffix(valid);
> +		u8 tile_id = xe ? gt_id_to_tile_id(xe, id) : 0;
>   
> -		if (!gt)
> -			goto unrecognized;
> -		snprintf(buf, size, "Tile%u: GT%u: ", gt->tile->id, id);
> +		pci_WARN(pdev, !valid && IS_ENABLED(CONFIG_DRM_XE_DEBUG),
> +			 "LOG: invalid GT identifier: %u\n", id);
> +		snprintf(buf, size, "Tile%u%s GT%u%s ", tile_id, pad, id, pad);
>   	} else {
>   		goto unrecognized;
>   	}

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