<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - Xorg segfault on cpu which does not support PAT" href="https://bugs.freedesktop.org/show_bug.cgi?id=110774#c4">Comment # 4</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - Xorg segfault on cpu which does not support PAT" href="https://bugs.freedesktop.org/show_bug.cgi?id=110774">bug 110774</a> from <a class="email" href="mailto:kenneth@whitecape.org" title="Kenneth Graunke <kenneth@whitecape.org>"> Kenneth Graunke</a> <pre>(In reply to Snir Sheriber from <a href="show_bug.cgi?id=110774#c3">comment #3</a>) > The kernel is already failing DRM_IOCTL_I915_GEM_MMAP with I915_MMAP_WC flag > if PAT is not supported so that brw_bo_map_wc returns null. > > I'm not familiar with this code nor the graphical stack but as i saw on > other code parts usually when brw_bo_map is called the returned value is > checked, in this case calling brw_bo_map assumes success, which results in > segfault. No, in almost all cases we assume maps work. In a few cases we do the bare minimum of punting the problem up to the caller, but in almost no case will it actually work out well. > (BTW is it possible to somehow not to avoid the gtt_map in this case?) In theory, we could blit everything via the 3D pipe every time we wanted to map a buffer, but that's expensive and impractical...in general, no, it's not really plausible to avoid mapping. I could certainly detect this case and fail to load the driver with a message, which is probably preferable to crashing...but do you need this case to work?</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>