On pe, 2015-08-14 at 14:11 +0100, Chris Wilson wrote: > On Fri, Aug 14, 2015 at 03:38:57PM +0300, Imre Deak wrote: > > Due to a coherency issue on BXT A steppings we can't guarantee a > > coherent view of cached GPU mappings, so fall back to uncached mappings. > > Note that this still won't fix cases where userspace expects a coherent > > view without synchronizing (via a set domain call). It still makes sense > > to limit the kernel's notion of the mapping to be uncached, for example > > for relocations to work properly during execbuffer time. Also in case > > user space does synchronize the buffer, this will still guarantee that > > we'll do the proper clflushing for the buffer. > > > > v2: > > - limit the WA to A steppings, on later stepping this HW issue is fixed > > This has to report the failure, ENODEV otherwise userspace will be > terribly confused (it will try to CPU coherent access assuming it will > be fast, when it is better to use alternative paths). Ok, I was not sure how existing user space would handle the failure, but if it has the fall-back logic then ENODEV is the better solution. Will change this. > -Chris > _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
