[PATCH] drm/xe/bmg: fix compressed VRAM handling

[Matthew Auld]

There looks to be an issue in our compression handling when the BO pages
are very fragmented, where we choose to skip the identity map and
instead fall back to emitting the PTEs by hand when migrating memory,
such that we can hopefully do more work per blit operation. However in
such a case we need to ensure the src PTEs are correctly tagged with a
compression enabled PAT index on dgpu xe2+, otherwise the copy will
simply treat the src memory as uncompressed, leading to corruption if
the memory was compressed by the user.

To fix this it looks like we can pass use_comp_pat into emit_pte() on
the src side.

There are reports of VRAM corruption in some heavy user workloads, which
might be related: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4495

Fixes: 523f191cc0c7 ("drm/xe/xe_migrate: Handle migration logic for xe2+ dgfx")
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Akshata Jahagirdar <akshata.jahagirdar at intel.com>
Cc: <stable at vger.kernel.org> # v6.12+
---
 drivers/gpu/drm/xe/xe_migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
index 8f8e9fdfb2a8..16788ecf924a 100644
--- a/drivers/gpu/drm/xe/xe_migrate.c
+++ b/drivers/gpu/drm/xe/xe_migrate.c
@@ -863,7 +863,7 @@ struct dma_fence *xe_migrate_copy(struct xe_migrate *m,
 		if (src_is_vram && xe_migrate_allow_identity(src_L0, &src_it))
 			xe_res_next(&src_it, src_L0);
 		else
-			emit_pte(m, bb, src_L0_pt, src_is_vram, copy_system_ccs,
+			emit_pte(m, bb, src_L0_pt, src_is_vram, copy_system_ccs || use_comp_pat,
 				 &src_it, src_L0, src);
 
 		if (dst_is_vram && xe_migrate_allow_identity(src_L0, &dst_it))
-- 
2.49.0