As an aid to understanding the lifetime of the drm_pagemaps used by the xe driver, document how the xe driver keeps the drm_pagemap references.
v3: - Fix formatting (Matt Brost) Suggested-by: Matthew Brost <[email protected]> Signed-off-by: Thomas Hellström <[email protected]> Reviewed-by: Matthew Brost <[email protected]> --- drivers/gpu/drm/xe/xe_svm.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c index 9eb288b8b57b..8d230eda3360 100644 --- a/drivers/gpu/drm/xe/xe_svm.c +++ b/drivers/gpu/drm/xe/xe_svm.c @@ -28,6 +28,27 @@ #define XE_PEER_PAGEMAP ((void *)0ul) #define XE_PEER_VM ((void *)1ul) +/** + * DOC: drm_pagemap reference-counting in xe: + * + * In addition to the drm_pagemap internal reference counting by its zone + * device data, the xe driver holds the following long-time references: + * + * - struct xe_pagemap: + * The xe_pagemap struct derives from struct drm_pagemap and uses its + * reference count. + * - SVM-enabled VMs: + * SVM-enabled VMs look up and keeps a reference to all xe_pagemaps on + * the same device. + * - VMAs: + * vmas keep a reference on the drm_pagemap indicated by a gpu_madvise() + * call. + * + * In addition, all drm_pagemap or xe_pagemap pointers where lifetime cannot + * be guaranteed by a vma reference under the vm lock should keep a reference. + * That includes the range->pages.dpagemap pointer. + */ + static int xe_svm_get_pagemaps(struct xe_vm *vm); void *xe_svm_private_page_owner(struct xe_vm *vm, bool force_smem) -- 2.51.1
