Re: [PATCH i-g-t v2 09/11] lib/intel_pat: Encapsulate management of xe_device's pat_cache

[Matt Atwood <matthew.s.atwood@intel.com>]

On Wed, Sep 23, 2026 at 06:41:16PM -0300, Gustavo Sousa wrote:
> Currently xe_device_get() manages the PAT cached information
> information by itself, by doing the necessary memory
> allocation/deallocation and calling xe_get_pat_sw_config() to
> initialize the cached information.
> 
> Such management is arguably better suited to be implemented as part of
> the intel_pat module and encapsulated such that xe_query doesn't need
> to know the details.
> 
> We will introduce changes that will require an extra logic for
> initializing the cache and having such encapsulation makes it much
> easier to implement.  Since we will touch this area, take this
> opportunity to move the existing management to intel_pat.
> 
> v2:
>   - Don't use void pointer as type of pat_cache. (Matt)
> 
> Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
> Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
> ---
>  lib/intel_pat.c   | 27 ++++++++++++++++++++++++++-
>  lib/intel_pat.h   |  5 +++++
>  lib/xe/xe_query.c |  9 ++-------
>  3 files changed, 33 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/intel_pat.c b/lib/intel_pat.c
> index da7ba1e51b16..db0f057cbd1e 100644
> --- a/lib/intel_pat.c
> +++ b/lib/intel_pat.c
> @@ -144,6 +144,31 @@ int32_t xe_get_pat_hw_config(int drm_fd, struct intel_pat_cache *xe_pat_cache, i
>  	return xe_get_pat_config(drm_fd, xe_pat_cache, gt, PAT_HW_CONFIG);
>  }
>  
> +void intel_pat_build_xe_cache(struct xe_device *xe_dev)
> +{
> +	struct intel_pat_cache *pat_cache;
> +
> +	pat_cache = calloc(1, sizeof(*pat_cache));
> +	igt_assert(pat_cache);
> +
> +	if (igt_debug_on(xe_get_pat_sw_config(xe_dev->fd, pat_cache, 0) <= 0)) {
> +		free(pat_cache);
> +		return;
> +	}
> +
> +	xe_dev->pat_cache = pat_cache;
> +}
> +
> +void intel_pat_free_xe_cache(struct xe_device *xe_dev)
> +{
> +	if (!xe_dev->pat_cache)
> +		return;
> +
> +	free(xe_dev->pat_cache);
> +
> +	xe_dev->pat_cache = NULL;
> +}
> +
>  /*
>   * Hardcoded PAT indices for Xe platforms, used as a fallback when the
>   * kernel doesn't expose gt0/pat_sw_config in debugfs.
> @@ -217,7 +242,7 @@ static void intel_get_pat_idx(int fd, struct intel_pat_cache *pat)
>  		struct xe_device *xe_dev = xe_device_get(fd);
>  
>  		if (xe_dev->pat_cache) {
> -			*pat = *xe_dev->pat_cache;
> +			*pat = *((struct intel_pat_cache *)xe_dev->pat_cache);
>  		} else if (xe_pat_fallback(fd, pat)) {
>  			igt_info("PAT sw_config debugfs not available, "
>  				 "using hardcoded fallback\n");
> diff --git a/lib/intel_pat.h b/lib/intel_pat.h
> index 52a61e8d25fb..fc8fa3fa9f45 100644
> --- a/lib/intel_pat.h
> +++ b/lib/intel_pat.h
> @@ -13,6 +13,8 @@
>  #define XE_PAT_IDX_INVALID ((uint8_t)-2) /* no such PAT index on this platform */
>  #define XE_PAT_MAX_ENTRIES 32
>  
> +struct xe_device;
> +
>  struct xe_pat_entry {
>  	uint32_t pat;
>  	bool rsvd;
> @@ -42,4 +44,7 @@ bool intel_has_pat_wt(int fd);
>  int32_t xe_get_pat_sw_config(int drm_fd, struct intel_pat_cache *xe_pat_cache, int gt);
>  int32_t xe_get_pat_hw_config(int drm_fd, struct intel_pat_cache *xe_pat_cache, int gt);
>  
> +void intel_pat_build_xe_cache(struct xe_device *xe_dev);
> +void intel_pat_free_xe_cache(struct xe_device *xe_dev);
> +
>  #endif /* INTEL_PAT_H */
> diff --git a/lib/xe/xe_query.c b/lib/xe/xe_query.c
> index d2c4329aa317..e7945c8923db 100644
> --- a/lib/xe/xe_query.c
> +++ b/lib/xe/xe_query.c
> @@ -377,8 +377,8 @@ static void xe_device_free(struct xe_device *xe_dev)
>  	free(xe_dev->mem_regions);
>  	free(xe_dev->vram_size);
>  	free(xe_dev->eu_stall);
> -	free(xe_dev->pat_cache);
>  
> +	intel_pat_free_xe_cache(xe_dev);
>  	xe_wa_free_cache(xe_dev);
>  
>  	free(xe_dev);
> @@ -458,12 +458,7 @@ struct xe_device *xe_device_get(int fd)
>  	 * should be extended to cache PAT entries by platform version/
>  	 * revision instead.
>  	 */
> -	xe_dev->pat_cache = calloc(1, sizeof(*xe_dev->pat_cache));
> -	igt_assert(xe_dev->pat_cache);
> -	if (xe_get_pat_sw_config(xe_dev->fd, xe_dev->pat_cache, 0) <= 0) {
> -		free(xe_dev->pat_cache);
> -		xe_dev->pat_cache = NULL;
> -	}
> +	intel_pat_build_xe_cache(xe_dev);
>  
>  	/* We may get here from multiple threads, use first cached xe_dev */
>  	pthread_mutex_lock(&cache.cache_mutex);
> 
> -- 
> 2.55.0
>