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.
Suggested-by: Matthew Brost <[email protected]> Signed-off-by: Thomas Hellström <[email protected]> --- drivers/gpu/drm/xe/xe_svm.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c index 56bb3896b89a..c1d6eb2f97d1 100644 --- a/drivers/gpu/drm/xe/xe_svm.c +++ b/drivers/gpu/drm/xe/xe_svm.c @@ -28,6 +28,28 @@ #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
