RE: [PATCH] lib/intel_pat: Handle platforms without compressed PAT index

Gurram, Pravalika
2026-03-03T09:50:48Z

> -----Original Message-----
> From: igt-dev <igt-dev-bounces@lists.freedesktop.org> On Behalf Of Sanjay
> Yadav
> Sent: Wednesday, 18 February, 2026 04:06 PM
> To: igt-dev@lists.freedesktop.org
> Cc: Auld, Matthew <matthew.auld@intel.com>
> Subject: [PATCH] lib/intel_pat: Handle platforms without compressed PAT
> index
>
> Previously intel_get_pat_idx_uc_comp() would silently return zero on
> platforms where no compressed PAT index exists (e.g. CRI), since uc_comp was
> zero-initialized by default. This could lead to incorrect behavior when callers
> assume the returned index is valid.
>
> Fix this by:
> - Adding XE_PAT_IDX_INVALID sentinel to detect unsupported platforms
> - Initializing uc_comp to XE_PAT_IDX_INVALID in intel_get_pat_idx();
> only platforms with CCS (graphics_ver 20/30) override it to a valid
> index
> - Adding igt_assert_f() in intel_get_pat_idx_uc_comp() to fail with
> a clear error instead of returning an invalid index
>
> Also update the bo-comp-disable-bind test to distinguish between "CCS is
> disabled" and "CCS does not exist" using HAS_FLATCCS(). On platforms
> without CCS, the compressed PAT bind check is skipped since there is no valid
> compressed PAT index to test with.
>
> Suggested-by: Matthew Auld <matthew.auld@intel.com>
> Signed-off-by: Sanjay Yadav <sanjay.kumar.yadav@intel.com>
> ---
> lib/intel_pat.c | 5 +++++
> lib/intel_pat.h | 1 +
> tests/intel/xe_pat.c | 30 ++++++++++++++++++++++--------
> 3 files changed, 28 insertions(+), 8 deletions(-)
>
> diff --git a/lib/intel_pat.c b/lib/intel_pat.c index 9815efc18..d30bee453
> 100644
> --- a/lib/intel_pat.c
> +++ b/lib/intel_pat.c
> @@ -98,6 +98,8 @@ static void intel_get_pat_idx(int fd, struct
> intel_pat_cache *pat) {
> uint16_t dev_id = intel_get_drm_devid(fd);
>
> + pat->uc_comp = XE_PAT_IDX_INVALID;
> +
> if (intel_graphics_ver(dev_id) == IP_VER(35, 11)) {
> pat->uc = 3;
> pat->wb = 2;
> @@ -155,8 +157,11 @@ uint8_t intel_get_pat_idx_uc_comp(int fd)
> uint16_t dev_id = intel_get_drm_devid(fd);
>
> igt_assert(intel_gen(dev_id) >= 20);
> + igt_assert(HAS_FLATCCS(dev_id));
>
> intel_get_pat_idx(fd, &pat);
> + igt_assert_f(pat.uc_comp != XE_PAT_IDX_INVALID,
> + "No compressed PAT index available on this platform\n");
> return pat.uc_comp;
> }
>
> diff --git a/lib/intel_pat.h b/lib/intel_pat.h index e9ade2e2e..e5dd8a0af
> 100644
> --- a/lib/intel_pat.h
> +++ b/lib/intel_pat.h
> @@ -10,6 +10,7 @@
> #include <stdint.h>
>
> #define DEFAULT_PAT_INDEX ((uint8_t)-1) /* igt-core can pick 1way or better
> */
> +#define XE_PAT_IDX_INVALID ((uint8_t)-2) /* no such PAT index on this
> +platform */
> #define XE_PAT_MAX_ENTRIES 32
>
> struct xe_pat_entry {
> diff --git a/tests/intel/xe_pat.c b/tests/intel/xe_pat.c index
> 21547c84e..052b7b699 100644
> --- a/tests/intel/xe_pat.c
> +++ b/tests/intel/xe_pat.c
> @@ -844,15 +844,18 @@ static bool has_no_compression_hint(int fd)
> * Test category: functionality test
> * Description: Validates that binding a BO created with
> * the NO_COMPRESSION flag using a compressed PAT index fails
> - * with -EINVAL on Xe2+ platforms.
> + * with -EINVAL on Xe2+ platforms. On platforms where CCS
> + * does not exist, the test verifies uncompressed access works.
> */
>
> static void bo_comp_disable_bind(int fd) {
> size_t size = xe_get_default_alignment(fd);
> - uint8_t comp_pat_index, uncomp_pat_index;
> - bool supported;
> + uint16_t dev_id = intel_get_drm_devid(fd);
> + bool has_flatccs = HAS_FLATCCS(dev_id);
> + uint8_t uncomp_pat_index;
> uint32_t vm, bo;
> + bool supported;
> int ret;
>
> supported = has_no_compression_hint(fd); @@ -868,14 +871,25
> @@ static void bo_comp_disable_bind(int fd)
> igt_assert_eq(ret, 0);
> vm = xe_vm_create(fd, 0, 0);
>
> - comp_pat_index = intel_get_pat_idx_uc_comp(fd);
> uncomp_pat_index = intel_get_pat_idx_uc(fd);
>
> - igt_assert_eq(__xe_vm_bind(fd, vm, 0, bo, 0, 0x100000,
> - size, 0, 0, NULL, 0,
> - 0, comp_pat_index, 0),
> - -EINVAL);
> + /*
> + * On platforms with CCS, binding a NO_COMPRESSION BO with a
> + * compressed PAT index must fail. On platforms without CCS,
> + * there is no valid compressed PAT index, so skip this check.
> + */
> + if (has_flatccs) {
> + uint8_t comp_pat_index = intel_get_pat_idx_uc_comp(fd);
> +
> + igt_assert_eq(__xe_vm_bind(fd, vm, 0, bo, 0, 0x100000,
> + size, 0, 0, NULL, 0,
> + 0, comp_pat_index, 0),
> + -EINVAL);
> + } else {
> + igt_debug("Platform has no CCS, skipping compressed PAT
> bind check\n");
> + }
Does this test needs to be skipped here? If yes you need to use igt_skip
And handle the resource cleanup
>
> + /* Uncompressed bind must always succeed */
> igt_assert_eq(__xe_vm_bind(fd, vm, 0, bo, 0, 0x100000,
> size, 0, 0, NULL, 0,
> 0, uncomp_pat_index, 0),
> --
> 2.52.0