<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_REOPENED " title="REOPENED - memcpy accessing GPU memory mappings using SSE instructions breaks in KVM" href="https://bugs.freedesktop.org/show_bug.cgi?id=111004#c11">Comment # 11</a> on <a class="bz_bug_link bz_status_REOPENED " title="REOPENED - memcpy accessing GPU memory mappings using SSE instructions breaks in KVM" href="https://bugs.freedesktop.org/show_bug.cgi?id=111004">bug 111004</a> from <a class="email" href="mailto:maxamar@mail.ru" title="maxamar@mail.ru">maxamar@mail.ru</a> <pre>(In reply to Christian König from <a href="show_bug.cgi?id=111004#c10">comment #10</a>) > Sorry but this is not a bug at all. > > As Michel already noted core Vulkan as well as some OpenGL/OpenCL extensions > mandate that the platform support all well aligned memory accesses to GPU > local memory (VRAM). > > If your platform (KVM in this case) can't do this for some reason you simply > can't use that platform with this software. > > In other words even if you replace memcpy/memset in Mesa with custom non SSE > versions it is perfectly valid for an application to use SSE to access VRAM. > And you can't change a binary application (which is actually just conforming > to a standard). > > The only possible workaround I can see in the driver is to not use VRAM at > all for CPU mappings. That's actually rather easily doable, but would > potentially cripple performance quite a bit. > > I can point you to the necessary bits of code if you are interested in that. Yes and somehow Mesa uses "movups" instruction which is: MOVUPS-Move Unaligned Packed Single-Precision Floating-Point So is a bug. Correct version is movaps which copies aligned data (is supported in KVM since long ago). Yes it is in glibc and what's so - don't use it then. KVM is part of Linux so must be supported. Anyway upgrading kernel to 4.17 seems to solve the problem, needs a test.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>