Am 27.09.2019 20:07 schrieb Ilia Mirkin <imirkin@xxxxxxxxxxxx>:
On Thu, Sep 26, 2019 at 5:44 PM Ben Skeggs <skeggsb@xxxxxxxxx> wrote:
>
> On Tue, 24 Sep 2019 at 22:19, Christian König
> <ckoenig.leichtzumerken@xxxxxxxxx> wrote:
> >
> > Hi guys,
> >
> > while working through more old TTM functionality I stumbled over the
> > io_reserve_lru.
> >
> > Basic idea is that when this flag is set the driver->io_mem_reserve()
> > callback can return -EAGAIN resulting in unmapping of other BOs.
> >
> > But Nouveau doesn't seem to return -EAGAIN in the call path of
> > io_mem_reserve anywhere.
> I believe this is a bug in Nouveau. We *should* be returning -EAGAIN
> if we fail to find space in BAR1 to map the BO into.
Could this lead to SIGBUS in userspace, esp related to resume and
similar situations?
Yes, I would say that's exactly what would happen.
Christian.
A user has been experiencing this in a
tricky-to-reproduce scenario with a ton of vram dedicated to
framebuffers and so on (3x 4K), and the nouveau ddx falls back to
memcpy in certain cases.
-ilia
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