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The fault handler returns SIGBUS to userspace, > matching i915 semantics. > > The purged check is added to both CPU fault paths: > - Fastpath (xe_bo_cpu_fault_fastpath): Returns error immediately > under dma-resv lock, preventing attempts to migrate/validate freed pages > - Slowpath (xe_bo_cpu_fault): Returns -EFAULT under drm_exec lock, > converted to VM_FAULT_SIGBUS > > Without the fastpath check, accessing existing mmap mappings of purged BOs > would trigger xe_bo_fault_migrate() on freed backing store, causing kernel > hangs or crashes. > > v2: > - Added xe_bo_is_purged(bo) instead of atomic_read. > - Avoids leaks and keeps drm_dev_exit() while returning. > > v3: > - Move xe_bo_is_purged check under a dma-resv lock (Matthew Brost) > > v4: > - Add purged check to fastpath (xe_bo_cpu_fault_fastpath) to prevent > hang when accessing existing mmap of purged BO > > Cc: Matthew Brost Reviewed-by: Matthew Brost > Cc: Thomas Hellström > Cc: Himal Prasad Ghimiray > Signed-off-by: Arvind Yadav > --- > drivers/gpu/drm/xe/xe_bo.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c > index d0a6d340b255..cc547915161d 100644 > --- a/drivers/gpu/drm/xe/xe_bo.c > +++ b/drivers/gpu/drm/xe/xe_bo.c > @@ -1934,6 +1934,12 @@ static vm_fault_t xe_bo_cpu_fault_fastpath(struct vm_fault *vmf, struct xe_devic > if (!dma_resv_trylock(tbo->base.resv)) > goto out_validation; > > + /* Purged BOs have no backing store - fault to userspace */ > + if (xe_bo_is_purged(bo)) { > + ret = VM_FAULT_SIGBUS; > + goto out_unlock; > + } > + > if (xe_ttm_bo_is_imported(tbo)) { > ret = VM_FAULT_SIGBUS; > drm_dbg(&xe->drm, "CPU trying to access an imported buffer object.\n"); > @@ -2024,6 +2030,12 @@ static vm_fault_t xe_bo_cpu_fault(struct vm_fault *vmf) > if (err) > break; > > + /* Purged BOs have no backing store - fault to userspace */ > + if (xe_bo_is_purged(bo)) { > + err = -EFAULT; > + break; > + } > + > if (xe_ttm_bo_is_imported(tbo)) { > err = -EFAULT; > drm_dbg(&xe->drm, "CPU trying to access an imported buffer object.\n"); > -- > 2.43.0 >