On Thu, Mar 19, 2015 at 03:22:42AM +0000, Song, Ruiling wrote: > > > Yeah, MAP_FIXED sounds a bit more ambitious and though I think it would > > work for OCL 2.0 pointer sharing, it's a little different than we were planning. > > To summarize, we have three possible approaches, each with its own > > problems: > > 1) simple patch to avoid binding at address 0 in PPGTT: > > does impact the ABI (though generally not in a harmful way), and > > may not be possible with aliasing PPGTT with e.g. framebuffers > > bound at offset 0 > > 2) exposing PIN_BIAS to userspace > > Would allow userspace to avoid pinning any buffers at offset 0 at > > execbuf time, but still has the problem with previously bound buffers > > and aliasing PPGTT > > 3) MAP_FIXED interface > > Flexible approach allowing userspace to manage its own virtual > > memory, but still has the same issues with aliasing PPGTT, and with > > shared contexts, which would have to negotiate between libraries > > how to > > handle the zero page > > > > For (1) and (2) the kernel pieces are really already in place, the main thing we > > need is a new flag to userspace to indicate behavior. I'd prefer (1) with a > > context creation flag to indicate "don't bind at 0". > > Execbuf would try to honor this, and userspace could check if any buffers > > ended up at 0 in the aliasing PPGTT case by checking the resulting offsets > > following the call. I expect in most cases this would be fine. > > > > It should be pretty easy to extend Ruiling's patch to use a context flag to > > determine the behavior; is that something you can do? Any objections to > > this approach? > > I am ok with adding a context flag to indicate "don't bind at 0". Any objections from others? > The patch is not from me, it is from David. I am not familiar with KMD. David, could you help on this patch? Yup, assuming, of course, that such an approach is acceptable. Kind regards, David _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
