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Re: [Qemu-devel] [PATCH] Experimental initial patch providing accelerate

From: Fabrice Bellard
Subject: Re: [Qemu-devel] [PATCH] Experimental initial patch providing accelerated OpenGL for Linux i386 (2nd attempt to post)
Date: Thu, 16 Nov 2006 23:41:51 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913


I find your patch interesting and I'll try to include it in QEMU ASAP.

My main remark is that the host/guest communication system must be changed and I can help you to implement it. I would prefer to use a PCI device and to avoid any i386 dependent code. For the PCI device, using the Bochs VGA adapter could be a possible idea. All the parameters and data should be transmitted as if the PCI device was doing DMA. A single I/O port could be used to start executing a list of OpenGL commands.

Once a basic Linux target OpenGL library is OK, it would be good to work on the equivalent Windows guest code by reusing the wine D3D code...



Even Rouault wrote:
Here's an attempt of providing accelerated OpenGL for QEMU.
I must underline first that it should really really be considered as experimental or a proof-of-concept. There's
still a lot of work to do to make it reliable and releasable.
So what is it exactly ?
- a patch for QEMU itself that intercepts any call to 'int $0x99' which is the interface I have chosen to dedicate to communication between guest user programs and QEMU. The modification of QEMU existing code is very slight.
  The essential of code on the guest side is in new files.
- a replacement libGL.so library that must be used inside the Linux guest. The library redirects guest OpenGL and GLX calls
  to host side, where your host libGL.so will do the real job.

It works currently only with Linux x86 as guest and host OS.

Now, the good news : which programs do currently work with this patch ?
- glxinfo
- glxgears. I get ~330 FPS with QEMU/GL (direct GLX), ~210 FPS through a SSH console on the guest OS (indirect GLX)
- some mesa demos programs.
* tunnel : ~26 FPS with QEMU/GL, ~3 FPS through a SSH console on the guest OS * teapot : ~50 FPS with QEMU/GL, ~7 FPS through a SSH console on the guest OS * fire : ~14 FPS with QEMU/GL, ~2 FPS through a SSH console on the guest OS * arbfplight : ~100 FPS with QEMU/GL, not possible through a SSH console on the guest OS (GL_ARB_vertex_program not available) - ... and ppracer ! (some crash from time to time. Starting at ~20 FPS at the beginning of the race, and finishing at ~10 FPS... strange...)

How fast is it ? Enough fast to have 15 FPS in ppracer with KQEMU disabled.
When KQEMU is enabled, paradoxically, the performance is really poor :-(

Successfully tested on the following platforms :
- Ubuntu Edgy x86 as host with ATI FGLRX driver / FC5 x86 as guest
- Ubuntu Dapper x86 as host with NVIDIA Proprietary driver / Ubuntu Dapper x86 as guest

Which programs do not work : probably most for the moment ;-)
I'd like to make it work with XGL (I've downloaded the latest Mandriva 2007 Live CD and I'm quite
impatient to enable the 3D in it) and GoogleEarth.

How to use it ? (ONLY on Linux i386 and with only i386-softmmu as target-list)
* Apply the patch and recompile QEMU * Lauch QEMU with -enable-gl option
* Get the compiled libGL.so from ./i386-softmmu and copy it to the guest OS
* In the guest OS : LD_LIBRARY_PATH=/path/to/replacement/libGL.so glxgears

TODO list :
- implement correctly full OpenGL API
- improve vertex arrays support
- maybe fix how the end of the guest process is detected
- make replacement libGL work when compiled with optimization flags
- integrate in a better way the window that popups on the guest side with the main qemu window - integrate it properly into QEMU build system (helper_opengl.c can't compile with -O2 : 'unable to find a register to spill in class `DIREG'') - understand why it's slower when KQEMU enabled and try to fix that if possible
- enable several guest OS processes to use OpenGL at the same time
- make it run on x86_64, and allowing any combination guest x86/x86_64 and host x86/x86_64, other archs
- port it to other UNIX-like OS with X
- improve security if possible (preventing malicious guest code from crashing host qemu)
- clean the code !
- much testing and debugging
- port it to Windows platform (first OpenGL / WGL, then D3D through Wine libs ?) - make a patch to Valgrind to make it happy with 'int $0x99' when running on guest side
- ...

The new files :
- opengl_client.c  : the OpenGL guest library
- helper_opengl.c : main guest-side code
- gl_func.h, server_stub.c, client_stub.c : generated files by parse_gl_h.c from gl.h parsing
- glgetv_cst.h  : generated file from parsing of a man page
- gl_func_perso.h, opengl_func.h : hand-written "prototypes"

In the mean time, enjoy !

PS :
I posted a similar message thursday, but it didn't get to the list apparently, maybe because of the two big attached patch (500 kB). I have reduced the size of the patch to 160 KB by not including generated source files. I will send it just after, so this message has a chance of coming. If you don't see a following message with the patch attached, I'll have to figure out where to store the patch...

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