QEMU README
===========
QEMU is a generic and open source machine & userspace emulator and
virtualizer.
QEMU is capable of emulating a complete machine in software without any
need for hardware virtualization support. By using dynamic translation,
it achieves very good performance. QEMU can also integrate with the Xen
and KVM hypervisors to provide emulated hardware while allowing the
hypervisor to manage the CPU. With hypervisor support, QEMU can achieve
near native performance for CPUs. When QEMU emulates CPUs directly it is
capable of running operating systems made for one machine (e.g. an ARMv7
board) on a different machine (e.g. an x86_64 PC board).
QEMU is also capable of providing userspace API virtualization for Linux
and BSD kernel interfaces. This allows binaries compiled against one
architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a
different architecture ABI (e.g. the Linux x86_64 ABI). This does not
involve any hardware emulation, simply CPU and syscall emulation.
QEMU aims to fit into a variety of use cases. It can be invoked directly
by users wishing to have full control over its behaviour and settings.
It also aims to facilitate integration into higher level management
layers, by providing a stable command line interface and monitor API.
It is commonly invoked indirectly via the libvirt library when using
open source applications such as oVirt, OpenStack and virt-manager.
QEMU as a whole is released under the GNU General Public License,
version 2. For full licensing details, consult the LICENSE file.
Building
========
QEMU is multi-platform software intended to be buildable on all modern
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
of other UNIX targets. The simple steps to build QEMU are:
mkdir build
cd build
../configure
make
Additional information can also be found online via the QEMU website:
https://qemu.org/Hosts/Linux
https://qemu.org/Hosts/Mac
https://qemu.org/Hosts/W32
Submitting patches
==================
The QEMU source code is maintained under the GIT version control system.
git clone git://git.qemu.org/qemu.git
When submitting patches, the preferred approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
guidelines set out in the HACKING and CODING_STYLE files.
Additional information on submitting patches can be found online via
the QEMU website
https://qemu.org/Contribute/SubmitAPatch
https://qemu.org/Contribute/TrivialPatches
Bug reporting
=============
The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:
https://bugs.launchpad.net/qemu/
If using QEMU via an operating system vendor pre-built binary package, it
is preferable to report bugs to the vendor's own bug tracker first. If
the bug is also known to affect latest upstream code, it can also be
reported via launchpad.
For additional information on bug reporting consult:
https://qemu.org/Contribute/ReportABug
Contact
=======
The QEMU community can be contacted in a number of ways, with the two
main methods being email and IRC
- qemu-devel@nongnu.org
https://lists.nongnu.org/mailman/listinfo/qemu-devel
- #qemu on irc.oftc.net
Information on additional methods of contacting the community can be
found online via the QEMU website:
https://qemu.org/Contribute/StartHere
-- End
Ed Swierk
authored
The device is supposed to maintain two distinct contexts for transmit offloads: one has parameters for both segmentation and checksum offload, the other only for checksum offload. The guest driver can send two context descriptors, one for each context (the TSE flag specifies which). Then the guest can refer to one or the other context in subsequent transmit data descriptors, depending on what offloads it wants applied to each packet. Currently the e1000 device stores just one context, and misinterprets the TSE flags in the context and data descriptors. This is often okay: Linux happens to send a fresh context descriptor before every data descriptor, so forgetting the other context doesn't matter. Windows does rely on separate contexts for TSO vs. non-TSO packets, but for mostly-TCP traffic the two contexts have identical TCP-specific offload parameters so confusing them doesn't matter. One case where this confusion matters is when a Windows guest sets up a TSO context for TCP and a non-TSO context for UDP, and then transmits both TCP and UDP traffic in parallel. The e1000 device sometimes ends up using TCP-specific parameters while doing checksum offload on a UDP datagram: it writes the checksum to offset 16 (the correct location for a TCP checksum), stomping on two bytes of UDP data, and leaving the wrong value in the actual UDP checksum field at offset 6. (Even worse, the host network stack may then recompute the UDP checksum, "correcting" it to match the corrupt data before sending it out a physical interface.) Correct this by tracking the TSO context independently of the non-TSO context, and selecting the appropriate context based on the TSE flag in each transmit data descriptor. Signed-off-by:Ed Swierk <eswierk@skyportsystems.com> Signed-off-by: