On Tue, 2021-05-25 at 12:00 +0100, Matthew Auld wrote:
On Fri, 21 May 2021 at 16:33, Thomas Hellström thomas.hellstrom@linux.intel.com wrote:
If the bo is idle when calling ttm_bo_pipeline_gutting(), we unnecessarily create a ghost object and push it out to delayed destroy. Fix this by adding a path for idle, and document the function.
Also avoid having the bo end up in a bad state vulnerable to user- space triggered kernel BUGs if the call to ttm_tt_create() fails.
Finally reuse ttm_bo_pipeline_gutting() in ttm_bo_evict().
Cc: Christian König christian.koenig@amd.com Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com
drivers/gpu/drm/ttm/ttm_bo.c | 20 ++++++------ drivers/gpu/drm/ttm/ttm_bo_util.c | 52 ++++++++++++++++++++++++++++--- drivers/gpu/drm/ttm/ttm_tt.c | 5 +++ include/drm/ttm/ttm_tt.h | 10 ++++++ 4 files changed, 73 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index ca1b098b6a56..a8fa3375b8aa 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -501,10 +501,15 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo, bdev->funcs->evict_flags(bo, &placement);
if (!placement.num_placement && !placement.num_busy_placement) { - ttm_bo_wait(bo, false, false); + ret = ttm_bo_wait(bo, true, false); + if (ret) + return ret;
- ttm_bo_cleanup_memtype_use(bo); - return ttm_tt_create(bo, false); + /* + * Since we've already synced, this frees backing store + * immediately. + */ + return ttm_bo_pipeline_gutting(bo); }
ret = ttm_bo_mem_space(bo, &placement, &evict_mem, ctx); @@ -974,13 +979,8 @@ int ttm_bo_validate(struct ttm_buffer_object *bo, /* * Remove the backing store if no placement is given. */ - if (!placement->num_placement && !placement-
num_busy_placement) {
- ret = ttm_bo_pipeline_gutting(bo); - if (ret) - return ret;
- return ttm_tt_create(bo, false); - } + if (!placement->num_placement && !placement-
num_busy_placement)
+ return ttm_bo_pipeline_gutting(bo);
/* * Check whether we need to move buffer. diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c index 4a7d3d672f9a..7fa9b3a852eb 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_util.c +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c @@ -585,26 +585,70 @@ int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo, } EXPORT_SYMBOL(ttm_bo_move_accel_cleanup);
+/**
- ttm_bo_pipeline_gutting - purge the contents of a bo
- @bo: The buffer object
- Purge the contents of a bo, async if the bo is not idle.
- After a successful call, the bo is left unpopulated in
- system placement. The function may wait uninterruptible
- for idle on OOM.
- Return: 0 if successful, negative error code on failure.
- */
int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo) { static const struct ttm_place sys_mem = { .mem_type = TTM_PL_SYSTEM }; struct ttm_buffer_object *ghost; + struct ttm_tt *ttm; int ret;
- ret = ttm_buffer_object_transfer(bo, &ghost); + /* If already idle, no need for ghost object dance. */ + ret = ttm_bo_wait(bo, false, true); + if (ret != -EBUSY) { + if (!bo->ttm) { + ret = ttm_tt_create(bo, true);
Why do we now unconditionally add clearing? Below also.
Here we've dropped the bo content and we add but do not populate a page vector. Now if someone resurrects this object we obtain new pages and those must be cleared, at least that's the intention.
/Thomas