On Wed, May 20, 2015 at 06:00:43PM +0200, Daniel Vetter wrote: > On Wed, May 20, 2015 at 03:14:06PM +0100, Chris Wilson wrote: > > On Wed, May 20, 2015 at 03:09:43PM +0100, Chris Wilson wrote: > > > On Wed, May 20, 2015 at 04:54:19PM +0300, David Weinehall wrote: > > > > This patch series (one patch each for libdrm, the kernel, and beignet) > > > > aims to provide a means to add a context-specific means to prevent > > > > a mapping to GPU virtual address zero. This is needed at least by > > > > Beignet (possibly in other use-cases too, though I don't know of any > > > > other) to allow use of address zero to represent NULL. > > > > > > Urm, you cannot allow absolute addressing period. What happens to the > > > object at 0 when the user reads from it or writes to it? You have to > > > have an object at 0 for the user's NULL pointer access. > > > > I'll mollify that: outside of full-ppgtt where you need to share the VM. > > The description is misleading, the new flag doesn't prevent anything from > getting mapped at 0 but only prevents any bo submitted through execbuf on > the given context from being bound at address 0. If that would happen > compute kernels using NULL checks for some things would fall over. That does not address the issue that *0 is an untrapped runtime bug that allows writing to other objects or reading from them. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
