Nouveau - Aug 2009 - concern about bo "pinned'ness" after gem pushbuf is done

As far as i see, we reserve the bo in the gem pushbuf ioctl, and
unreserve after the pushbuf and the fence have been emitted. This
assumption holds if bo moves happen on the same channel or if a cpu
copy happens and we're waiting on fences. But for nv50 it is very
common for the bo move to happen on the kernel fifo, which does not
guarantee anything. Is there any safety i missed?

Maarten.

On Sun, 2009-08-23 at 01:21 +0200, Maarten Maathuis
wrote:
> As far as i see, we reserve the bo in the gem pushbuf ioctl, and
> unreserve after the pushbuf and the fence have been emitted. This
> assumption holds if bo moves happen on the same channel or if a cpu
> copy happens and we're waiting on fences. But for nv50 it is very
> common for the bo move to happen on the kernel fifo, which does not
> guarantee anything. Is there any safety i missed?
Hm, access by another channel after the move will definitely be
protected as we emit a fence for the move operation.

However, I think we may need to wait ourselves if the buffer move is
going to happen on a channel other than whatever used it last.  TTM
doesn't do this anymore I believe (the old ttm used to).

Ben.
> 
> Maarten.
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