Re: [PATCH v2 4/4] drm/qxl: use qxl pin function

[Christian König]

Am 29.09.20 um 12:53 schrieb Daniel Vetter:
> On Tue, Sep 29, 2020 at 11:51:15AM +0200, Gerd Hoffmann wrote:
> > Otherwise ttm throws a WARN because we try to pin without a reservation.
> >
> > Fixes: 9d36d4320462 ("drm/qxl: switch over to the new pin interface")
> > Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/qxl/qxl_object.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/qxl/qxl_object.c b/drivers/gpu/drm/qxl/qxl_object.c
> > index d3635e3e3267..eb45267d51db 100644
> > --- a/drivers/gpu/drm/qxl/qxl_object.c
> > +++ b/drivers/gpu/drm/qxl/qxl_object.c
> > @@ -145,7 +145,7 @@ int qxl_bo_create(struct qxl_device *qdev,
> >   		return r;
> >   	}
> >   	if (pinned)
> > -		ttm_bo_pin(&bo->tbo);
> > +		qxl_bo_pin(bo);
> I think this is now after ttm_bo_init, and at that point the object is
> visible to lru users and everything. So I do think you need to grab locks
> here instead of just incrementing the pin count alone.
>
> It's also I think a bit racy, since ttm_bo_init drops the lock, so someone
> might have snuck in and evicted the object already.
>
> I think what you need is to call ttm_bo_init_reserved, then ttm_bo_pin,
> then ttm_bo_unreserve, all explicitly.

Ah, yes Daniel is right. I thought I've fixed that up, but looks like I 
only did that for VMWGFX.

Sorry for the noise, fix to correctly address this is underway.

Regards,
Christian.

> -Daniel
>
> >   	*bo_ptr = bo;
> >   	return 0;
> >   }
> > --
> > 2.27.0