From: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= <thomas.hellstrom@linux.intel.com>
To: intel-xe@lists.freedesktop.org
Cc: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= <thomas.hellstrom@linux.intel.com>,
	Matthew Brost <matthew.brost@intel.com>,
	Matthew Auld <matthew.auld@intel.com>,
	stable@vger.kernel.org
Subject: [PATCH] drm/xe: Attempt to bring bos back to VRAM after eviction
Date: Thu, 28 Aug 2025 17:42:19 +0200
Message-ID: <20250828154219.4889-1-thomas.hellstrom@linux.intel.com>
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VRAM+TT bos that are evicted from VRAM to TT may remain in
TT also after a revalidation following eviction or suspend.

This manifests itself as applications becoming sluggish
after buffer objects get evicted or after a resume from
suspend or hibernation.

If the bo supports placement in both VRAM and TT, and
we are on DGFX, mark the TT placement as fallback. This means
that it is tried only after VRAM + eviction.

This flaw has probably been present since the xe module was
upstreamed but use a Fixes: commit below where backporting is
likely to be simple. For earlier versions we need to open-
code the fallback algorithm in the driver.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5995
Fixes: a78a8da51b36 ("drm/ttm: replace busy placement with flags v6")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: <stable@vger.kernel.org> # v6.9+
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/xe/xe_bo.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 4faf15d5fa6d..64dea4e478bd 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -188,6 +188,8 @@ static void try_add_system(struct xe_device *xe, struct xe_bo *bo,
 
 		bo->placements[*c] = (struct ttm_place) {
 			.mem_type = XE_PL_TT,
+			.flags = (IS_DGFX(xe) && (bo_flags & XE_BO_FLAG_VRAM_MASK)) ?
+			TTM_PL_FLAG_FALLBACK : 0,
 		};
 		*c += 1;
 	}
-- 
2.50.1