Am 28.05.21 um 09:33 schrieb Thomas Hellström:
On Fri, 2021-05-28 at 09:16 +0200, Christian König wrote:
Am 27.05.21 um 17:51 schrieb Thomas Hellström:
On Thu, 2021-05-27 at 17:32 +0200, Christian König wrote:
Am 27.05.21 um 17:05 schrieb Thomas Hellström:
On Thu, 2021-05-27 at 17:01 +0200, Thomas Hellström wrote:
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,
In fact, we'd probably might want to take the !bo->ttm bos off
the
LRU
as well..
No, we don't want to take any BOs of the LRU unless they are
pinned.
Adding a TT object or populating it doesn't necessarily put the
BO
back
to the LRU.
OK, but swapped bos are also taken off the LRU list so these
unpopulated bos are just taking the same path. Only difference to
swapped is that they don't get read back on re-populate, but
typically
cleared.
But what would be the point of keeping swapped-out bos on the LRU
list?, particularly when we're iterating under a spinlock?
Shouldn't we try to re-add to LRU (if not already on an LRU) just
before populating? There aren't really that many calls in core TTM.
I want to avoid removing BOs from the LRU as much as possible since
we
forgot on multiple places that we want to re-add them.
Conceptual I think the swapped BOs should have a separate memory
domain,
this way we can ignore them cleanly when swapping things out.
Yes, that would of course work as well. Keeping them on the system LRU
is IMO highly undesirable.
Going to pick this patch up, modifying it a bit more and then pushing
it
to drm-misc-fixes for upstreaming.
OK, I dropped the TTM fix for the purge-in-swap-notify from the i915
series, hoping that the reworked variant of this patch lands first.
You will still need to add the second ttm_tt_populated() check since I
dropped that for the back which I want to push to -fixes.
Regards,
Christian.
Thanks,
Thomas
Thanks,
Christian.
/Thomas
Christian.
/Thomas
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