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python/machine.py: split shutdown into hard and soft flavors
John Snow authored 
This is done primarily to avoid the 'bare except' pattern, which
suppresses all exceptions during shutdown and can obscure errors.

Replace this with a pattern that isolates the different kind of shutdown
paradigms (_hard_shutdown and _soft_shutdown), and a new fallback shutdown
handler (_do_shutdown) that gracefully attempts one before the other.

This split now also ensures that no matter what happens,
_post_shutdown() is always invoked.

shutdown() changes in behavior such that if it attempts to do a graceful
shutdown and is unable to, it will now always raise an exception to
indicate this. This can be avoided by the test writer in three ways:

1. If the VM is expected to have already exited or is in the process of
exiting, wait() can be used instead of shutdown() to clean up resources
instead. This helps avoid race conditions in shutdown.

2. If a test writer is expecting graceful shutdown to fail, shutdown
should be called in a try...except block.

3. If the test writer has no interest in performing a graceful shutdown
at all, kill() can be used instead.

Handling shutdown in this way makes it much more explicit which type of
shutdown we want and allows the library to report problems with this
process.

Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: default avatarCleber Rosa <crosa@redhat.com>
Tested-by: default avatarCleber Rosa <crosa@redhat.com>
Message-Id: <20200710050649.32434-11-jsnow@redhat.com>
Signed-off-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
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VERSION
block.c
blockdev-nbd.c
blockdev.c
blockjob.c
bootdevice.c
configure
cpus-common.c
device_tree.c
disas.c
dma-helpers.c
exec-vary.c
exec.c
gdbstub.c
gitdm.config
hmp-commands-info.hx
hmp-commands.hx
iothread.c
job-qmp.c
job.c
memory_ldst.inc.c
module-common.c
os-posix.c
os-win32.c
README.rst

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:

Submitting patches

The QEMU source code is maintained under the GIT version control system.

git clone https://git.qemu.org/git/qemu.git

When submitting patches, one common 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 CODING_STYLE.rst file.

Additional information on submitting patches can be found online via the QEMU website

The QEMU website is also maintained under source control.

git clone https://git.qemu.org/git/qemu-web.git

A 'git-publish' utility was created to make above process less cumbersome, and is highly recommended for making regular contributions, or even just for sending consecutive patch series revisions. It also requires a working 'git send-email' setup, and by default doesn't automate everything, so you may want to go through the above steps manually for once.

For installation instructions, please go to

The workflow with 'git-publish' is:

$ git checkout master -b my-feature
$ # work on new commits, add your 'Signed-off-by' lines to each
$ git publish

Your patch series will be sent and tagged as my-feature-v1 if you need to refer back to it in the future.

Sending v2:

$ git checkout my-feature # same topic branch
$ # making changes to the commits (using 'git rebase', for example)
$ git publish

Your patch series will be sent with 'v2' tag in the subject and the git tip will be tagged as my-feature-v2.

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:

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:

Contact

The QEMU community can be contacted in a number of ways, with the two main methods being email and IRC

Information on additional methods of contacting the community can be found online via the QEMU website: