On Thu, Jul 07, 2016 at 09:41:12AM +0100, Chris Wilson wrote: > This effectively reverts > > commit afcd950cafea6e27b739fe7772cbbeed37d05b8b > Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Date: Wed Jun 10 15:58:01 2015 +0100 > > drm: Avoid the double clflush on the last cache line in drm_clflush_virt_range() > > as we have observed issues with serialisation of the clflush operations > on Baytrail+ Atoms with partial updates. Applying the double flush on the > last cacheline forces that clflush to be ordered with respect to the > previous clflush, and the mfence then protects against prefetches crossing > the clflush boundary. > > The same issue can be demonstrated in userspace with igt/gem_exec_flush. > > Fixes: afcd950cafea6 (drm: Avoid the double clflush on the last cache...) > Testcase: igt/gem_concurrent_blit > Testcase: igt/gem_partial_pread_pwrite > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92845 > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx > Cc: Akash Goel <akash.goel@xxxxxxxxx> > Cc: Imre Deak <imre.deak@xxxxxxxxx> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > Cc: Jason Ekstrand <jason.ekstrand@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> It's duct-tape, but oh well. Applied to drm-misc. -Daniel > --- > drivers/gpu/drm/drm_cache.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c > index 059f7c39c582..a7916e5f8864 100644 > --- a/drivers/gpu/drm/drm_cache.c > +++ b/drivers/gpu/drm/drm_cache.c > @@ -136,6 +136,7 @@ drm_clflush_virt_range(void *addr, unsigned long length) > mb(); > for (; addr < end; addr += size) > clflushopt(addr); > + clflushopt(end - 1); /* force serialisation */ > mb(); > return; > } > -- > 2.8.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html