Am 27.05.21 um 17:01 schrieb Thomas Hellström:
On Thu, 2021-05-27 at 16:54 +0200, Christian König wrote:
Am 27.05.21 um 16:19 schrieb Thomas Hellström:
The swapping code was dereference bo->ttm pointers without having
the
dma-resv lock held. Also it might try to swap out unpopulated bos.
Fix this by moving the bo->ttm dereference until we have the
reservation
lock. Check that the ttm_tt is populated after the swap_notify
callback.
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo.c | 16 +++++++++++++++-
drivers/gpu/drm/ttm/ttm_device.c | 8 +++-----
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
b/drivers/gpu/drm/ttm/ttm_bo.c
index 9f53506a82fc..86213d37657b 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -1163,6 +1163,16 @@ int ttm_bo_swapout(struct ttm_buffer_object
*bo, struct ttm_operation_ctx *ctx,
if (!ttm_bo_evict_swapout_allowable(bo, ctx, &place,
&locked, NULL))
return -EBUSY;
+ dma_resv_assert_held(bo->base.resv);
+
+ if (!bo->ttm ||
+ bo->ttm->page_flags & TTM_PAGE_FLAG_SG ||
+ bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED) {
+ if (locked)
+ dma_resv_unlock(bo->base.resv);
+ return -EBUSY;
+ }
+
if (!ttm_bo_get_unless_zero(bo)) {
if (locked)
dma_resv_unlock(bo->base.resv);
@@ -1215,7 +1225,8 @@ int ttm_bo_swapout(struct ttm_buffer_object
*bo, struct ttm_operation_ctx *ctx,
if (bo->bdev->funcs->swap_notify)
bo->bdev->funcs->swap_notify(bo);
- ret = ttm_tt_swapout(bo->bdev, bo->ttm, gfp_flags);
+ if (ttm_tt_is_populated(bo->ttm))
+ ret = ttm_tt_swapout(bo->bdev, bo->ttm, gfp_flags);
Exactly that is what I won't recommend. We would try to swap out the
same BO over and over again with that.
But we wouldn't since the BO is taken off the LRU and never re-added,
Well then that would be a bug in itself.
Why not move that to the check above as well?
Because the BO may become unpopulated in swap_notify(), i915, like
vmwgfx, sometimes sets up gpu bindings from system, and when we get a
notification from user-space that those are purgeable, we don't want to
purge immediately but wait for a potential swapout.
Uff, good point. But then we need to check that at both locations I think.
Because populating the TT object currently doesn't put the BO back on
the LRU eventually.
Christian.
/Thomas
Christian.
out:
/*
@@ -1225,6 +1236,9 @@ int ttm_bo_swapout(struct ttm_buffer_object
*bo, struct ttm_operation_ctx *ctx,
if (locked)
dma_resv_unlock(bo->base.resv);
ttm_bo_put(bo);
+
+ /* Don't break locking rules. */
+ WARN_ON(ret == -EBUSY);
return ret;
}
diff --git a/drivers/gpu/drm/ttm/ttm_device.c
b/drivers/gpu/drm/ttm/ttm_device.c
index 460953dcad11..eaa7487ae404 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -143,14 +143,12 @@ int ttm_device_swapout(struct ttm_device
*bdev, struct ttm_operation_ctx *ctx,
for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
list_for_each_entry(bo, &man->lru[j], lru)
{
- uint32_t num_pages;
+ pgoff_t num_pages;
- if (!bo->ttm ||
- bo->ttm->page_flags &
TTM_PAGE_FLAG_SG ||
- bo->ttm->page_flags &
TTM_PAGE_FLAG_SWAPPED)
+ if (!READ_ONCE(bo->ttm))
continue;
- num_pages = bo->ttm->num_pages;
+ num_pages = bo->base.size >>
PAGE_SHIFT;
ret = ttm_bo_swapout(bo, ctx,
gfp_flags);
/* ttm_bo_swapout has dropped the
lru_lock */
if (!ret)
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