99a767c5d9
There's been a longstanding bug in the IRQ handling code in the Metalkit version of the SVGA reference driver, which occasionally caused tests to hang. I looked at the disassembly of SVGA_WaitForIRQ and friends, and I found one big problem and one smaller problem: The 'switchContext' flag is used to tell the IRQ handler whether it should branch to the saved context or not. This value *must* be written before we halt, or we can deadlock. Unfortunately, the value wasn't marked as 'volatile', and the compiler was optimizing out this assignment entirely! This means that 'flags' will never get set, and we'll be in an infinite loop. Given this bug, I'm not sure why WaitForIRQ ever worked. It's possible that we were fine if the IRQ had already arrived by the time WaitForIRQ was called, but we'd deadlock if we actually ended up waiting. If this is the case, it also means that fence-stress isn't doing a very good job of stressing the IRQ code. The other, much less severe problem: The stack frames for WaitForIRQInternal and SaveContext may have been partially overlapping, since gcc was allocating 0x10 bytes on the stack before calling SaveContext. The proper solution is probably just to rewrite all of this in assembly, but for now I just increased the number of padding words on the stack by adding extra NULL parameters to WaitForIRQInternal. |
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README.txt |
-------------------------------- VMware SVGA Device Developer Kit -------------------------------- The "VMware SVGA II" device is the virtual graphics card implemented by all VMware virtualization products. It is a virtual PCI device, which implements a basic 2D framebuffer, as well as 3D acceleration, video overlay acceleration, and hardware cursor support. This is a package of documentation and example code for the VMware SVGA device's programming model. Currently it consists of some very basic documentation, and a collection of examples which illustrate the more advanced features of the device. These examples are written to run on the "virtual bare metal", without an operating system. This package is intended for educational purposes, or for people who are developing 3D drivers. This code won't help you if you're writing normal user-level apps that you'd like to run inside a virtual machine. It's for driver authors, and it assumes a reasonable amount of prior knowledge about graphics hardware. Requirements ------------ To compile the example code, you'll need a few basic open source tools: - A recent version of GCC. I use 4.2. Older versions may require tweaking the Makefile.rules file slightly.) - binutils - GNU Make - Python To run the examples, you'll need a recent version of VMware Workstation, Player, or Fusion. Some of the examples will work on older versions, but Workstation 6.5.x or Fusion 2.0.x is strongly recommended. Contents -------- * bin/ Precompiled binaries and .vmx files for all examples. These can be loaded directly into VMware Workstation, Player, or Fusion. * doc/ Basic SVGA hardware documentation. This includes a text file with information about the programming model, plus it includes a copy of a WIOV paper which describes our 3D acceleration architecture. * lib/metalkit/ Metalkit is a very simple open source OS, which bootstraps the examples and provides basic hardware support. * lib/refdriver/ The SVGA "Reference Driver". This is a sample implementation of a driver for our device, which is used by the examples. It provides device initialiation, an implementation of the low-level FIFO protocol, and wrappers around common FIFO commands. If you're writing a driver for the VMware SVGA device, "svga.c" from this directory is required reading. The FIFO protocol has many subtle gotchas, and this source file is the only place where they're publicly documented. * lib/vmware/ Header files which define VMware's protocols and virtual hardware. The svga_reg.h and svga3d_reg.h files are (in places, at least) commented with more information on the programming model. If you can't find specific documentation or an example on a feature, this is the next place to look. This is also where to get a complete list of the supported registers and commands. * lib/util/ Higher-level utilities built on top of the refdriver layer. This directory won't contain any novel information about the virtual hardware, but it does contain some higher-level abstractions used by the examples, and these abstractions demonstrate some useful idioms for programming the SVGA device. * examples/ Each example has a separate subdirectory. You can run "make" in the top-level directory to compile all examples, or you can build them individually. Many of the examples are self-explanatory, but some of them are not. See the comments at the beginning of the 'main.c' file in each example. Development ----------- This project isn't intended to be a one-time "code drop" from VMware. Our intent is for the examples in this package to be maintained out in the open. If we have a bugfix, or a new example that works on released VMware products, we'll check it in directly to the public repository. For examples of not-yet-released features, we will be developing on an internal branch. This branch will be merged to the public repository shortly after the first release which has working versions of these features. License ------- Except where noted in individual source files, the whole package is Copyright (C) 1998-2009 VMware, Inc. It is released under the MIT license: Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Contact ------- This project is provided as-is, with no official support from VMware. However, I will try to answer questions as time permits. If you have questions or you'd like to submit a patch, feel free to email me at: micah at vmware.com --