[Intel-gfx] [PATCH 1/5] drm/i915: Round up object allocations

[Chris Wilson]

On Sun, Jan 26, 2014 at 10:17:57AM +0100, Daniel Vetter wrote:
> On Sun, Jan 26, 2014 at 6:49 AM, Ben Widawsky <ben at bwidawsk.net> wrote:
> > On Sat, Jan 25, 2014 at 09:28:24PM +0100, Daniel Vetter wrote:
> >> On Thu, Jan 23, 2014 at 07:21:10PM -0800, Ben Widawsky wrote:
> >> > DRM gets very mad when you request an object which occupies a partial
> >> > page. As a DRM driver, i915 never really wants to anger DRM, and would
> >> > always just want the rounding done for us.
> >> >
> >> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> >> > ---
> >> >  drivers/gpu/drm/i915/i915_gem.c | 2 ++
> >> >  1 file changed, 2 insertions(+)
> >> >
> >> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> >> > index 024e454..8cd1134 100644
> >> > --- a/drivers/gpu/drm/i915/i915_gem.c
> >> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> >> > @@ -4168,6 +4168,8 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
> >> >     struct address_space *mapping;
> >> >     gfp_t mask;
> >> >
> >> > +   size = round_up(size, PAGE_SIZE);
> >> > +
> >>
> >> Nope, if there's some code that doesn't do page-aligend bo allocations it
> >> needs to be fixed there. If you want throw a WARN_ON and early return in
> >> here.
> >> -Daniel
> >
> > Why?
> 
> Because allocating a non-page aligned gem bo is a bug. All current
> in-kernel allocations are already aligned. I've thought that we also
> reject unaligned request from userspace but apparently we help out
> since forever (i.e. gem was merged). Might be worth a shot to turn
> that into an -EINVAL if libdrm does the right rounding ...

We already have an -EINVAL guard on our create ioctl(s).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre