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This manifested as rendering failures or sometimes GPU hangs in
compositors when they accidentally got MSAA visuals due to a bug in the X
Server. Today we decided that the problem in compositors was equivalent
to a corruption bug we'd noticed recently in resizing MSAA-visual
glxgears, and debugging got a lot easier.
When we allocate our MCS MT, libdrm takes the size we request, aligns it
to Y tile size (blowing it up from 300x300=900000 bytes to 384*320=122880
bytes, 30 pages), then puts it into a power-of-two-sized BO (131072 bytes,
32 pages). Because it's Y tiled, we attach a 384-byte-stride fence to it.
When we memset by the BO size in Mesa, between bytes 122880 and 131072 the
data gets stored to the first 20 or so scanlines of each of the 3 tiled
pages in that row, even though only 2 of those pages were allocated by
libdrm. In the glxgears case, the missing 3rd page happened to
consistently be the static VBO that got mapped right after the first MCS
allocation, so corruption only appeared once window resize made us throw
out the old MCS and then allocate the same BO to back the new MCS.
Instead, just memset the amount of data we actually asked libdrm to
allocate for, which will be smaller (more efficient) and not overrun.
Thanks go to Kenneth for doing most of the hard debugging to eliminate a
lot of the search space for the bug.
Cc: "10.0 10.1" <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77207
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
(cherry picked from commit
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File: docs/README.WIN32 Last updated: 21 June 2013 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons osmesa mesagdi to build classic mesa Windows GDI drivers; or scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. Recipe ------ Building on windows requires several open-source packages. These are steps that work as of this writing. 1) install python 2.7 2) install scons (latest) 3) install mingw, flex, and bison 4) install libxml2 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get libxml2-python-2.9.1.win-amd64-py2.7.exe 5) install pywin32 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get pywin32-218.4.win-amd64-py2.7.exe 6) install git 7) download mesa from git see http://www.mesa3d.org/repository.html 8) run scons General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.