[PATCH v3 1/2] drm/gem: drm_gem_dumb_map_offset(): reject dma-buf

[Daniel Vetter]

On Thu, Aug 24, 2017 at 11:04:01AM +0100, Brian Starkey wrote:
> Hi,
> 
> Thanks for the CC.
> 
> On Fri, Aug 18, 2017 at 06:13:14PM +0200, Noralf Tr??nnes wrote:
> > (cc affected parties)
> > 
> > 
> > Den 18.08.2017 09.46, skrev Daniel Vetter:
> > > On Thu, Aug 17, 2017 at 06:21:30PM +0200, Noralf Tr??nnes wrote:
> > > > Reject mapping an imported dma-buf since is's an invalid use-case.
> > > > 
> > > > Cc: Philipp Zabel <p.zabel at pengutronix.de>
> > > > Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > > > Cc: Sean Paul <seanpaul at chromium.org>
> > > > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > > Signed-off-by: Noralf Tr??nnes <noralf at tronnes.org>
> > > I think acks from someone using mali would be good too. amdgpu already has
> > > such checks, so I think on the desktop side we're ok.
> > > 
> 
> This looks like it would break anyone running the Mali-4xx series GPUs
> with the Arm graphics stack (e.g. Hikey board).
> 
> I don't know where that sits in terms of policy.

Why would this break this use-case? Is the mali blob somehow using dumb
mmap for it's own buffers it shares with display? That would be rather
backwards ...

Either way, blob -> meh, not a concern really.
-Daniel

> 
> Cheers,
> -Brian
> 
> > > Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > 
> > > But I think this one here definitely needs a few more acks. I could break
> > > uabi if we're unlucky, so let's not rush it.
> > 
> > Ok, I've CC'ed the affected parties to increase the odds that they look
> > at this. These are the drivers using drm_gem_dumb_map_offset()
> > (hopefully I got the list right):
> > 
> > arc
> > atmel-hlcdc
> > cirrus
> > exynos
> > fsl-dcu
> > gma500
> > hdlcd
> > imx
> > kirin
> > mali-dp
> > mediatek
> > meson
> > mxsfb
> > pl111
> > rcar-du
> > rockchip
> > shmobile
> > sti
> > stm
> > sun4i
> > tegra
> > tilcd
> > vc4
> > zte
> > 
> > 
> > Noralf.
> > 
> > > -Daniel
> > > 
> > > > ---
> > > >  drivers/gpu/drm/drm_gem.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > > 
> > > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> > > > index ad4e9cf..8da5801 100644
> > > > --- a/drivers/gpu/drm/drm_gem.c
> > > > +++ b/drivers/gpu/drm/drm_gem.c
> > > > @@ -333,6 +333,12 @@ int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
> > > >  	if (!obj)
> > > >  		return -ENOENT;
> > > > +	/* Don't allow imported objects to be mapped */
> > > > +	if (obj->import_attach) {
> > > > +		ret = -EINVAL;
> > > > +		goto out;
> > > > +	}
> > > > +
> > > >  	ret = drm_gem_create_mmap_offset(obj);
> > > >  	if (ret)
> > > >  		goto out;
> > > > -- 
> > > > 2.7.4
> > > > 
> > 

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