On Thu, Oct 01, 2015 at 02:24:53PM +0100, Chris Wilson wrote: > On Thu, Oct 01, 2015 at 03:37:21PM +0300, Ville Syrjälä wrote: > > On Thu, Oct 01, 2015 at 12:57:10PM +0100, Chris Wilson wrote: > > > - while (cmd < batch_end) { > > > - const struct drm_i915_cmd_descriptor *desc; > > > - u32 length; > > > + k = i; > > > + if (k > PAGE_SIZE - out) > > > + k = PAGE_SIZE - out; > > > + if (k == PAGE_SIZE) > > > + copy_page(dst, src); > > > + else > > > + memcpy(dst + out, src + j, k); > > > + > > > + out += k; > > > + j += k; > > > + i -= k; > > > + } while (i); > > > + > > > + cmd = src + in; > > > > So you're now checking the src batch? What prevents userspace from > > overwriting it with eg. NOPS between the time you copied it and the > > time you check it? > > Zilch. I picked src as it was already in the CPU cache, whereas dst will > be WC later. To satisfy you and byt, I need to stage the copy into a > temporary page, scan it, then copy into dst. > > The silver lining is that it does remove some lines of code. I'm pretty > confident that the double copy should not be noticed if I remember about > the cache-trashing of kunmap and carefully manage that. Yeah, I was thinking that optimally we'd do the copy+scan in cacheline units, but maybe that's too small to make it actually efficient? -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx