On 25/06/15 18:51, Chris Wilson wrote: > On Thu, Jun 25, 2015 at 06:35:14PM +0300, Mika Kuoppala wrote: >> During review of dynamic page tables series, I was able >> to hit a lite restore bug with execlists. I assume that >> due to incorrect pd, the batch run out of legit address space >> and into the scratch page area. The ACTHD was increasing >> due to scratch being all zeroes (MI_NOOPs). And as gen8 >> address space is quite large, the hangcheck happily waited >> for a long long time, keeping the process effectively stuck. >> >> According to Chris Wilson any modern gpu will grind to halt >> if it encounters commands of all ones. This seemed to do the >> trick and hang was declared promptly when the gpu wandered into >> the scratch land. >> >> v2: Use 0xffff00ff pattern (Chris) > > Thinking about this, could we add a scratch page checker to hangcheck? > Just check the first/last u64 perhaps? Or random offset_in_page? > -Chris I've suggested to Tomas that when running in 32-bit PPGTT mode, if ACTHD is >4G then it's definitely broken. Doesn't help much once PPGTT space expands to 48b though. .Dave. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
