[PATCH 0/3] drm/xe/ggtt: fix stale GGTT mappings on unmap

From: Tangudu Tilak Tirumalesh <[email protected]>

This series addresses two related GGTT teardown issues on multi-
queue platforms:

First issue: the unmap path mapped freed ranges to the scratch page.
Because scratch is a valid PTE, a re-walk of a freed range never
faults, so any stale TLB translation left behind is masked - the freed
range silently reads scratch instead of surfacing the problem. On
multi-queue platforms Patch 1 writes PTE=0 on unmap instead; other
platforms keep scratch, so free-hole and init-time handling are
unchanged.

Second issue: engines cache GGTT translations in their own TLBs. The
existing GGTT invalidation (xe_tlb_inval_ggtt()) does not reach those
engine-side TLBs, so after an unmap an engine can keep hitting the
stale translation and read the old page. Patches 2 and 3 add and use a
FULL_INTRA_VF invalidation to drain the engine TLBs on unmap.

Patch 1: drm/xe/ggtt: stop mapping unmapped GGTT pages to scratch
    On multi-queue platforms write PTE=0 on unmap so a stale-TLB
    access to a freed range faults instead of silently landing on
    scratch.

Patch 2: drm/xe/tlb_inval: add FULL_INTRA_VF GGTT invalidation helper
    xe_tlb_inval_ggtt_full() + GuC backend flush engine TLBs across
    all engines in the requesting VF partition.

Patch 3: drm/xe/ggtt: invalidate engine GGTT TLBs for multi-queue GTs
    Issue the FULL_INTRA_VF invalidation on the unmap path, gated on
    the GT having any multi-queue engine class. Draining the engine
    TLB on teardown guarantees a recycled range's next occupant cannot
    hit the predecessor's cached translation.

Tangudu Tilak Tirumalesh (3):
  drm/xe/ggtt: stop mapping unmapped GGTT pages to scratch
  drm/xe/tlb_inval: add FULL_INTRA_VF GGTT invalidation helper
  drm/xe/ggtt: invalidate engine GGTT TLBs for multi-queue GTs

 drivers/gpu/drm/xe/xe_ggtt.c            | 61 +++++++++++++++++++------
 drivers/gpu/drm/xe/xe_guc_tlb_inval.c   | 21 +++++++++
 drivers/gpu/drm/xe/xe_tlb_inval.c       | 25 ++++++++++
 drivers/gpu/drm/xe/xe_tlb_inval.h       |  1 +
 drivers/gpu/drm/xe/xe_tlb_inval_types.h | 10 ++++
 5 files changed, 104 insertions(+), 14 deletions(-)

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2.46.0