<html> <head> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> </head> <body bgcolor="#FFFFFF" text="#000000"> <div class="moz-cite-prefix">Am 12.12.2016 um 16:20 schrieb Nicolai Hähnle: </div> <blockquote cite="mid:9153dde6-9087-94b0-a062-dd223e5f381a@gmail.com" type="cite">Hi all, I just sent out two patches that hopefully make the kernel module more robust in the face of page table shadows being swapped out. However, even with those patches, I can still fairly reliably reproduce crashes with a backtrace of the shape amdgpu_cs_ioctl -> amdgpu_vm_update_page_directory -> amdgpu_ttm_bind -> amdgpu_gtt_mgr_alloc The plausible reason for these crashes is that nothing seems to prevent the shadow BOs from being moved between the calls to amdgpu_cs_validate in amdgpu_cs_parser_bos and the calls to amdgpu_ttm_bind. </blockquote> The shadow BOs use the same reservation object than the real BOs. So as long as the real BOs can't be evicted the shadows can't be evicted either. <blockquote cite="mid:9153dde6-9087-94b0-a062-dd223e5f381a@gmail.com" type="cite"> The attached patch has fixed these crashes for me so far, but it's very heavy-handed: it collects all page table shadows and the page directory shadow and adds them all to the reservations for the callers of amdgpu_vm_update_page_directory. </blockquote> That is most likely just a timing change, cause the shadows should end up in the duplicates list anyway. So the patch shouldn't have any effect. <blockquote cite="mid:9153dde6-9087-94b0-a062-dd223e5f381a@gmail.com" type="cite"> I feel like there should be a better way. In part, I wonder why the shadows are needed in the first place. I vaguely recall the discussions about GPU reset and such, but I don't remember why the page tables can't just be rebuilt in some other way. </blockquote> It's just the simplest and fastest way to keep a copy of the page tables around. The problem with rebuilding the page tables from the mappings is that the housekeeping structures already have the future state when a reset happens, not the state we need to rebuild the tables. We could obviously change the housekeeping a bit to keep both states, but that would complicate mapping and unmapping of BOs significantly. Regards, Christian. <blockquote cite="mid:9153dde6-9087-94b0-a062-dd223e5f381a@gmail.com" type="cite"> Cheers, Nicolai <fieldset class="mimeAttachmentHeader"></fieldset> <pre wrap="">_______________________________________________ amd-gfx mailing list <a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a> <a class="moz-txt-link-freetext" href="https://lists.freedesktop.org/mailman/listinfo/amd-gfx">https://lists.freedesktop.org/mailman/listinfo/amd-gfx</a> </pre> </blockquote> </body> </html>