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Eric Blake 009cd86650 nbd/server: Support a request payload
Upcoming additions to support NBD 64-bit effect lengths allow for the
possibility to distinguish between payload length (capped at 32M) and
effect length (64 bits, although we generally assume 63 bits because
of off_t limitations).  Without that extension, only the NBD_CMD_WRITE
request has a payload; but with the extension, it makes sense to allow
at least NBD_CMD_BLOCK_STATUS to have both a payload and effect length
in a future patch (where the payload is a limited-size struct that in
turn gives the real effect length as well as a subset of known ids for
which status is requested).  Other future NBD commands may also have a
request payload, so the 64-bit extension introduces a new
NBD_CMD_FLAG_PAYLOAD_LEN that distinguishes between whether the header
length is a payload length or an effect length, rather than
hard-coding the decision based on the command.

According to the spec, a client should never send a command with a
payload without the negotiation phase proving such extension is
available.  So in the unlikely event the bit is set or cleared
incorrectly, the client is already at fault; if the client then
provides the payload, we can gracefully consume it off the wire and
fail the command with NBD_EINVAL (subsequent checks for magic numbers
ensure we are still in sync), while if the client fails to send
payload we block waiting for it (basically deadlocking our connection
to the bad client, but not negatively impacting our ability to service
other clients, so not a security risk).  Note that we do not support
the payload version of BLOCK_STATUS yet.

This patch also fixes a latent bug introduced in b2578459: once
request->len can be 64 bits, assigning it to a 32-bit payload_len can
cause wraparound to 0 which then sets req->complete prematurely;
thankfully, the bug was not possible back then (it takes this and
later patches to even allow request->len larger than 32 bits; and
since previously the only 'payload_len = request->len' assignment was
in NBD_CMD_WRITE which also sets check_length, which in turn rejects
lengths larger than 32M before relying on any possibly-truncated value
stored in payload_len).

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20230925192229.3186470-15-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
[eblake: enhance comment on handling client error, fix type bug]
Signed-off-by: Eric Blake <eblake@redhat.com>
2023-10-05 11:02:08 -05:00
.github/workflows
.gitlab/issue_templates
.gitlab-ci.d gitlab: make Cirrus CI jobs gating 2023-09-20 15:06:33 +01:00
accel tcg: Split out tcg init functions to tcg/startup.h 2023-10-04 11:03:54 -07:00
audio audio: forbid default audiodev backend with -nodefaults 2023-10-03 10:29:40 +02:00
authz
backends Block patches 2023-09-21 09:05:10 -04:00
block block: Clean up local variable shadowing 2023-09-29 08:13:57 +02:00
bsd-user accel: Introduce AccelClass::cpu_common_[un]realize 2023-10-05 08:55:34 -04:00
chardev chardev/char-pty: Avoid losing bytes when the other side just (re-)connected 2023-10-03 15:40:09 +04:00
common-user
configs target/loongarch: Add GDB support for loongarch32 mode 2023-08-24 11:17:56 +08:00
contrib elf2dmp: rework PDB_STREAM_INDEXES::segments obtaining 2023-09-21 16:13:54 +01:00
crypto * fix from optionrom build 2023-10-03 07:43:44 -04:00
disas disas/m68k: clean up local variable shadowing 2023-09-29 10:07:21 +02:00
docs virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
dump dump: kdump-zlib data pages not dumped with pvtime/aarch64 2023-08-07 15:46:59 +04:00
ebpf trace-events: Fix the name of the tracing.rst file 2023-09-08 13:08:51 +03:00
fpu fpu: Handle m68k extended precision denormals properly 2023-09-16 14:57:16 +00:00
fsdev fsdev: Use ThrottleDirection instread of bool is_write 2023-08-29 10:49:24 +02:00
gdb-xml target/loongarch: Split fcc register to fcc0-7 in gdbstub 2023-08-24 11:17:59 +08:00
gdbstub accel/tcg: Replace CPUState.env_ptr with cpu_env() 2023-10-04 11:03:54 -07:00
host/include i386: spelling fixes 2023-09-20 07:54:34 +03:00
hw virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
include virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
io io: follow coroutine AioContext in qio_channel_yield() 2023-09-07 20:32:11 -05:00
libdecnumber
linux-headers linux-headers: Update to Linux v6.6-rc1 2023-09-12 11:34:56 +02:00
linux-user build: Remove --enable-gprof 2023-10-04 11:03:54 -07:00
migration migration: Unify and trace vmstate field_exists() checks 2023-10-04 13:19:47 +02:00
monitor accel/tcg: Replace CPUState.env_ptr with cpu_env() 2023-10-04 11:03:54 -07:00
nbd nbd/server: Support a request payload 2023-10-05 11:02:08 -05:00
net virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
pc-bios optionrom: Remove build-id section 2023-09-29 09:33:09 +02:00
plugins plugin: Simplify struct qemu_plugin_hwaddr 2023-09-16 14:57:15 +00:00
po
python tests/avocado: Fix console data loss 2023-09-20 15:06:33 +01:00
qapi qemu-img: map: report compressed data blocks 2023-09-20 17:46:01 +02:00
qga qga/: spelling fixes 2023-09-08 13:08:52 +03:00
qobject docs/interop: Convert qmp-spec.txt to rST 2023-05-22 10:21:01 +02:00
qom qom: Propagate alignment through type system 2023-10-03 08:01:02 -07:00
replay meson: Replace softmmu_ss -> system_ss 2023-06-20 10:01:30 +02:00
roms seabios: remove PCI drivers from bios.bin 2023-09-25 18:25:03 +02:00
scripts accel: Introduce AccelClass::cpu_common_[un]realize 2023-10-05 08:55:34 -04:00
scsi io: follow coroutine AioContext in qio_channel_yield() 2023-09-07 20:32:11 -05:00
semihosting accel/tcg: Replace CPUState.env_ptr with cpu_env() 2023-10-04 11:03:54 -07:00
softmmu accel/tcg: Make icount.o a target agnostic unit 2023-10-04 11:03:54 -07:00
stats meson: Replace softmmu_ss -> system_ss 2023-06-20 10:01:30 +02:00
storage-daemon configure, meson: remove target OS symbols from config-host.mak 2023-09-07 13:32:37 +02:00
stubs stubs/colo.c: spelling 2023-08-07 13:52:59 +03:00
subprojects libvhost-user: handle shared_object msg 2023-10-04 18:15:06 -04:00
target accel/tcg: Remove cpu_set_cpustate_pointers 2023-10-04 11:03:54 -07:00
tcg tcg/loongarch64: Fix buid error 2023-10-04 11:03:54 -07:00
tests virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
tools
trace meson: Replace softmmu_ss -> system_ss 2023-06-20 10:01:30 +02:00
ui Misc fixes and cleanups 2023-10-04 12:51:26 -04:00
util virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
.dir-locals.el
.editorconfig
.exrc
.gdbinit
.git-blame-ignore-revs
.gitattributes
.gitignore configure: rename --enable-pypi to --enable-download, control subprojects too 2023-06-06 16:30:01 +02:00
.gitlab-ci.yml
.gitmodules meson: subprojects: replace berkeley-{soft,test}float-3 with wraps 2023-06-06 16:30:01 +02:00
.gitpublish
.mailmap mailmap: Fix BALATON Zoltan author email 2023-10-05 11:02:08 -05:00
.patchew.yml
.readthedocs.yml
.travis.yml
block.c block: Clean up local variable shadowing 2023-09-29 08:13:57 +02:00
blockdev-nbd.c
blockdev.c block: Mark bdrv_add/del_child() and caller GRAPH_WRLOCK 2023-09-20 17:46:01 +02:00
blockjob.c block: Mark bdrv_root_unref_child() GRAPH_WRLOCK 2023-09-20 17:46:01 +02:00
configure Python: Drop support for Python 3.7 2023-09-07 13:32:37 +02:00
COPYING
COPYING.LIB
cpu-common.c exec: Rename cpu.c -> cpu-target.c 2023-10-04 11:03:54 -07:00
cpu-target.c exec: Rename cpu.c -> cpu-target.c 2023-10-04 11:03:54 -07:00
event-loop-base.c
gitdm.config
hmp-commands-info.hx accel/tcg: remove CONFIG_PROFILER 2023-06-26 17:33:00 +02:00
hmp-commands.hx net: add initial support for AF_XDP network backend 2023-09-18 14:36:13 +08:00
iothread.c iothread: Set the GSource "name" field 2023-09-07 14:01:25 -04:00
job-qmp.c
job.c
Kconfig
Kconfig.host
LICENSE
MAINTAINERS virtio,pci: features, cleanups 2023-10-05 09:01:01 -04:00
Makefile configure, meson: remove target OS symbols from config-host.mak 2023-09-07 13:32:37 +02:00
memory_ldst.c.inc
meson_options.txt build: Remove --enable-gprof 2023-10-04 11:03:54 -07:00
meson.build accel: Introduce AccelClass::cpu_common_[un]realize 2023-10-05 08:55:34 -04:00
module-common.c
os-posix.c os-posix.c: remove unneeded #includes 2023-09-01 23:46:20 +02:00
os-win32.c
page-vary-common.c
page-vary-target.c exec: Rename target specific page-vary.c -> page-vary-target.c 2023-10-04 11:03:54 -07:00
pythondeps.toml Revert "tests: Use separate virtual environment for avocado" 2023-08-28 09:55:48 +02:00
qemu-bridge-helper.c
qemu-edid.c
qemu-img-cmds.hx
qemu-img.c qemu-img: map: report compressed data blocks 2023-09-20 17:46:01 +02:00
qemu-io-cmds.c
qemu-io.c
qemu-keymap.c qemu-keymap: properly check return from xkb_keymap_mod_get_index 2023-07-03 12:51:21 +01:00
qemu-nbd.c qemu-nbd: changes towards enabling -Wshadow=local 2023-09-29 10:07:20 +02:00
qemu-options.hx migration: file URI offset 2023-10-04 13:18:08 +02:00
qemu.nsi
qemu.sasl
README.rst
replication.c
trace-events trace-events: remove the remaining vcpu trace events 2023-06-01 11:05:05 -04:00
VERSION Open 8.2 development tree 2023-08-22 07:14:07 -07:00
version.rc

===========
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.


Documentation
=============

Documentation can be found hosted online at
`<https://www.qemu.org/documentation/>`_. The documentation for the
current development version that is available at
`<https://www.qemu.org/docs/master/>`_ is generated from the ``docs/``
folder in the source tree, and is built by `Sphinx
<https://www.sphinx-doc.org/en/master/>`_.


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:


.. code-block:: shell

  mkdir build
  cd build
  ../configure
  make

Additional information can also be found online via the QEMU website:

* `<https://wiki.qemu.org/Hosts/Linux>`_
* `<https://wiki.qemu.org/Hosts/Mac>`_
* `<https://wiki.qemu.org/Hosts/W32>`_


Submitting patches
==================

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

.. code-block:: shell

   git clone https://gitlab.com/qemu-project/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 `style section
<https://www.qemu.org/docs/master/devel/style.html>`_ of
the Developers Guide.

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

* `<https://wiki.qemu.org/Contribute/SubmitAPatch>`_
* `<https://wiki.qemu.org/Contribute/TrivialPatches>`_

The QEMU website is also maintained under source control.

.. code-block:: shell

  git clone https://gitlab.com/qemu-project/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:

.. code-block:: shell

  $ 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:

.. code-block:: shell

  $ 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 GitLab issues to track bugs. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:

* `<https://gitlab.com/qemu-project/qemu/-/issues>`_

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 GitLab.

For additional information on bug reporting consult:

* `<https://wiki.qemu.org/Contribute/ReportABug>`_


ChangeLog
=========

For version history and release notes, please visit
`<https://wiki.qemu.org/ChangeLog/>`_ or look at the git history for
more detailed information.


Contact
=======

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

* `<mailto: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://wiki.qemu.org/Contribute/StartHere>`_