On Fri, Jan 22, 2021 at 2:35 PM Gerd Hoffmann [off-list ref] wrote:

On Fri, Jan 22, 2021 at 09:13:42AM +0100, Thomas Zimmermann wrote:

quoted

Hi

Am 20.01.21 um 12:12 schrieb Gerd Hoffmann:

quoted

Balances the qxl_create_bo(..., pinned=true, ...);
call in qxl_release_bo_alloc().

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
  drivers/gpu/drm/qxl/qxl_release.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c
index 0fcfc952d5e9..add979cba11b 100644
--- a/drivers/gpu/drm/qxl/qxl_release.c
+++ b/drivers/gpu/drm/qxl/qxl_release.c

@@ -166,6 +166,7 @@ qxl_release_free_list(struct qxl_release *release)
            entry = container_of(release->bos.next,
                                 struct qxl_bo_list, tv.head);
            bo = to_qxl_bo(entry->tv.bo);
+           bo->tbo.pin_count = 0; /* ttm_bo_unpin(&bo->tbo); */

This code looks like a workaround or a bug.

AFAICT the only place with pre-pinned BO is qdev->dumb_shadow_bo. Can you
remove the pinned flag entirely and handle pinning as part of
dumb_shadow_bo's code.

No, the release objects are pinned too, and they must be
pinned (qxl commands are in there, and references are
placed in the qxl rings, so allowing them to roam is
a non-starter).

quoted

if (pin_count)
    ttm_bo_unpin();
WARN_ON(pin_count); /* should always be 0 now */

Well, the pin_count is 1 at this point.
No need for the if().

Just calling ttm_bo_unpin() here makes lockdep unhappy.

How does that one splat? But yeah if that's a problem should be
explained in the comment. I'd then also only do a pin_count--; to make
sure you can still catch other pin leaks if you have them. Setting it
to 0 kinda defeats the warning.
-Daniel

Not calling ttm_bo_unpin() makes ttm_bo_release() throw
a WARN() because of the pin.

Clearing pin_count (which is how ttm fixes things up
in the error path) works.

I'm open to better ideas.

take care,
  Gerd

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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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