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Kevin Wolf 061ca8a368 block: Convert .bdrv_truncate callback to coroutine_fn
bdrv_truncate() is an operation that can block (even for a quite long
time, depending on the PreallocMode) in I/O paths that shouldn't block.
Convert it to a coroutine_fn so that we have the infrastructure for
drivers to make their .bdrv_co_truncate implementation asynchronous.

This change could potentially introduce new race conditions because
bdrv_truncate() isn't necessarily executed atomically any more. Whether
this is a problem needs to be evaluated for each block driver that
supports truncate:

* file-posix/win32, gluster, iscsi, nfs, rbd, ssh, sheepdog: The
  protocol drivers are trivially safe because they don't actually yield
  yet, so there is no change in behaviour.

* copy-on-read, crypto, raw-format: Essentially just filter drivers that
  pass the request to a child node, no problem.

* qcow2: The implementation modifies metadata, so it needs to hold
  s->lock to be safe with concurrent I/O requests. In order to avoid
  double locking, this requires pulling the locking out into
  preallocate_co() and using qcow2_write_caches() instead of
  bdrv_flush().

* qed: Does a single header update, this is fine without locking.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2018-06-29 14:20:56 +02:00
accel Pull request 2018-06-28 16:28:22 +01:00
audio audio: Convert use of atoi to qemu_strtoi 2018-06-25 14:03:30 +02:00
backends
block block: Convert .bdrv_truncate callback to coroutine_fn 2018-06-29 14:20:56 +02:00
bsd-user
capstone@22ead3e0bf
chardev socket: don't free msgfds if error equals EAGAIN 2018-06-28 13:36:59 +01:00
contrib
crypto
default-configs target-arm queue: 2018-06-22 16:03:31 +01:00
disas
docs trace: forbid floating point types 2018-06-27 11:09:29 +01:00
dtc@e54388015a
fpu
fsdev
gdb-xml
hw hw/block/nvme: add optional parameter num_queues for nvme device 2018-06-29 14:20:56 +02:00
include block: Convert .bdrv_truncate callback to coroutine_fn 2018-06-29 14:20:56 +02:00
io Delete AF_UNIX socket after close 2018-06-28 13:36:59 +01:00
libdecnumber
linux-headers linux-headers: Update to kernel mainline commit b357bf602 2018-06-22 13:28:35 +01:00
linux-user
migration migration/next for 20180627 2018-06-28 15:31:42 +01:00
nbd nbd/server: Silence gcc false positive 2018-06-22 14:18:36 +01:00
net
pc-bios pseries: Update SLOF firmware image to qemu-slof-20180621 2018-06-22 14:19:07 +10:00
po
qapi qapi/job: The next release will be 3.0 2018-06-29 14:20:56 +02:00
qga
qobject block-qdict: Pacify Coverity after commit f1b34a248e 2018-06-29 14:20:56 +02:00
qom
replay
roms pseries: Update SLOF firmware image to qemu-slof-20180621 2018-06-22 14:19:07 +10:00
scripts trace: forbid floating point types 2018-06-27 11:09:29 +01:00
scsi
slirp
stubs linux-aio: properly bubble up errors from initialization 2018-06-27 13:06:34 +01:00
target Pull request 2018-06-28 16:28:22 +01:00
tcg
tests ahci: fix FIS I bit and PIO Setup FIS interrupt 2018-06-25 16:50:48 -04:00
trace trace: add trace_mem_build_info_no_se_be/le 2018-06-27 11:09:24 +01:00
ui sdl2: add checking for NULL 2018-06-26 13:48:49 +02:00
util linux-aio: properly bubble up errors from initialization 2018-06-27 13:06:34 +01:00
.dir-locals.el
.editorconfig
.exrc
.gdbinit
.gitignore
.gitmodules
.gitpublish
.mailmap
.shippable.yml
.travis.yml
arch_init.c
balloon.c
block.c block: Convert .bdrv_truncate callback to coroutine_fn 2018-06-29 14:20:56 +02:00
blockdev-nbd.c qapi: new qmp command nbd-server-add-bitmap 2018-06-21 09:23:59 -05:00
blockdev.c
blockjob.c
bootdevice.c
bt-host.c
bt-vhci.c
Changelog
CODING_STYLE
configure
COPYING
COPYING.LIB
cpus-common.c
cpus.c tcg: fix --disable-tcg build breakage 2018-06-22 18:55:24 +01:00
device_tree.c
device-hotplug.c
disas.c
dma-helpers.c
dump.c
exec.c postcopy: drop ram_pages parameter from postcopy_ram_incoming_init() 2018-06-27 13:28:31 +02:00
gdbstub.c
HACKING
hmp-commands-info.hx hmp: Add commands for preconfig 2018-06-21 13:16:48 +01:00
hmp-commands.hx hmp: add exit_preconfig 2018-06-21 13:18:05 +01:00
hmp.c migration: Create multifd_bytes ram_counter 2018-06-27 13:28:11 +02:00
hmp.h hmp: add exit_preconfig 2018-06-21 13:18:05 +01:00
ioport.c
iothread.c
job-qmp.c
job.c
LICENSE
MAINTAINERS MAINTAINERS: update target-mips maintainers 2018-06-27 20:10:42 +02:00
Makefile Revert commit d4e5ec877c 2018-06-22 16:33:47 +02:00
Makefile.objs
Makefile.target
memory_ldst.inc.c
memory_mapping.c
memory.c
module-common.c
monitor.c hmp: Allow HMP in preconfig state again 2018-06-21 13:18:11 +01:00
numa.c
os-posix.c
os-win32.c
qdev-monitor.c
qdict-test-data.txt
qemu-bridge-helper.c
qemu-doc.texi hw/i386: Deprecate the machine types pc-0.10 and pc-0.11 2018-06-25 14:10:01 -03:00
qemu-ga.texi
qemu-img-cmds.hx
qemu-img.c
qemu-img.texi
qemu-io-cmds.c
qemu-io.c
qemu-keymap.c
qemu-nbd.c
qemu-nbd.texi
qemu-option-trace.texi
qemu-options-wrapper.h
qemu-options.h
qemu-options.hx
qemu-seccomp.c
qemu-tech.texi
qemu.nsi
qemu.sasl
qmp.c
qtest.c
README
replication.c
replication.h
rules.mak
thunk.c
tpm.c
trace-events
VERSION
version.rc
vl.c hw/i386: Deprecate the machine types pc-0.10 and pc-0.11 2018-06-25 14:10:01 -03:00

         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, 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 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

The QEMU website is also maintained under source control.

  git clone git://git.qemu.org/qemu-web.git
  https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/

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

  https://github.com/stefanha/git-publish

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:

  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