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Vladimir Sementsov-Ogievskiy f34b2bcf8c block: use int64_t instead of int in driver write_zeroes handlers
We are generally moving to int64_t for both offset and bytes parameters
on all io paths.

Main motivation is realization of 64-bit write_zeroes operation for
fast zeroing large disk chunks, up to the whole disk.

We chose signed type, to be consistent with off_t (which is signed) and
with possibility for signed return type (where negative value means
error).

So, convert driver write_zeroes handlers bytes parameter to int64_t.

The only caller of all updated function is bdrv_co_do_pwrite_zeroes().

bdrv_co_do_pwrite_zeroes() itself is of course OK with widening of
callee parameter type. Also, bdrv_co_do_pwrite_zeroes()'s
max_write_zeroes is limited to INT_MAX. So, updated functions all are
safe, they will not get "bytes" larger than before.

Still, let's look through all updated functions, and add assertions to
the ones which are actually unprepared to values larger than INT_MAX.
For these drivers also set explicit max_pwrite_zeroes limit.

Let's go:

blkdebug: calculations can't overflow, thanks to
  bdrv_check_qiov_request() in generic layer. rule_check() and
  bdrv_co_pwrite_zeroes() both have 64bit argument.

blklogwrites: pass to blk_log_writes_co_log() with 64bit argument.

blkreplay, copy-on-read, filter-compress: pass to
  bdrv_co_pwrite_zeroes() which is OK

copy-before-write: Calls cbw_do_copy_before_write() and
  bdrv_co_pwrite_zeroes, both have 64bit argument.

file-posix: both handler calls raw_do_pwrite_zeroes, which is updated.
  In raw_do_pwrite_zeroes() calculations are OK due to
  bdrv_check_qiov_request(), bytes go to RawPosixAIOData::aio_nbytes
  which is uint64_t.
  Check also where that uint64_t gets handed:
  handle_aiocb_write_zeroes_block() passes a uint64_t[2] to
  ioctl(BLKZEROOUT), handle_aiocb_write_zeroes() calls do_fallocate()
  which takes off_t (and we compile to always have 64-bit off_t), as
  does handle_aiocb_write_zeroes_unmap. All look safe.

gluster: bytes go to GlusterAIOCB::size which is int64_t and to
  glfs_zerofill_async works with off_t.

iscsi: Aha, here we deal with iscsi_writesame16_task() that has
  uint32_t num_blocks argument and iscsi_writesame16_task() has
  uint16_t argument. Make comments, add assertions and clarify
  max_pwrite_zeroes calculation.
  iscsi_allocmap_() functions already has int64_t argument
  is_byte_request_lun_aligned is simple to update, do it.

mirror_top: pass to bdrv_mirror_top_do_write which has uint64_t
  argument

nbd: Aha, here we have protocol limitation, and NBDRequest::len is
  uint32_t. max_pwrite_zeroes is cleanly set to 32bit value, so we are
  OK for now.

nvme: Again, protocol limitation. And no inherent limit for
  write-zeroes at all. But from code that calculates cdw12 it's obvious
  that we do have limit and alignment. Let's clarify it. Also,
  obviously the code is not prepared to handle bytes=0. Let's handle
  this case too.
  trace events already 64bit

preallocate: pass to handle_write() and bdrv_co_pwrite_zeroes(), both
  64bit.

rbd: pass to qemu_rbd_start_co() which is 64bit.

qcow2: offset + bytes and alignment still works good (thanks to
  bdrv_check_qiov_request()), so tail calculation is OK
  qcow2_subcluster_zeroize() has 64bit argument, should be OK
  trace events updated

qed: qed_co_request wants int nb_sectors. Also in code we have size_t
  used for request length which may be 32bit. So, let's just keep
  INT_MAX as a limit (aligning it down to pwrite_zeroes_alignment) and
  don't care.

raw-format: Is OK. raw_adjust_offset and bdrv_co_pwrite_zeroes are both
  64bit.

throttle: Both throttle_group_co_io_limits_intercept() and
  bdrv_co_pwrite_zeroes() are 64bit.

vmdk: pass to vmdk_pwritev which is 64bit

quorum: pass to quorum_co_pwritev() which is 64bit

Hooray!

At this point all block drivers are prepared to support 64bit
write-zero requests, or have explicitly set max_pwrite_zeroes.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210903102807.27127-8-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: use <= rather than < in assertions relying on max_pwrite_zeroes]
Signed-off-by: Eric Blake <eblake@redhat.com>
2021-09-29 13:46:32 -05:00
.github Update documentation to refer to new location for issues 2021-06-21 05:43:11 +02:00
.gitlab/issue_templates GitLab: Add "Feature Request" issue template. 2021-06-25 10:08:37 +01:00
.gitlab-ci.d gitlab-ci: Mark manual-only jobs as allow_failure 2021-09-15 16:43:16 +01:00
accel accel/tcg: Restrict cpu_handle_halt() to sysemu 2021-09-21 19:36:44 -07:00
audio audio: Never send migration section 2021-08-10 10:55:57 +02:00
authz configure, meson: convert pam detection to meson 2021-06-25 10:54:10 +02:00
backends qapi: Convert simple union TpmTypeOptions to flat one 2021-09-27 08:22:25 +02:00
block block: use int64_t instead of int in driver write_zeroes handlers 2021-09-29 13:46:32 -05:00
bsd-user user: Remove cpu_get_pic_interrupt() stubs 2021-09-14 12:00:21 -07:00
capstone@f8b1b83301 capstone: Update to upstream "next" branch 2020-10-03 04:23:14 -05:00
chardev qapi: Convert simple union SocketAddressLegacy to flat one 2021-09-27 08:23:25 +02:00
configs hw/acpi: refactor acpi hp modules so that targets can just use what they need 2021-09-04 09:07:46 -04:00
contrib elf2dmp: Fail cleanly if PDB file specifies zero block_size 2021-09-20 09:54:32 +01:00
crypto crypto: add gnutls pbkdf provider 2021-07-14 14:15:52 +01:00
disas Hexagon (disas/hexagon.c) fix memory leak for early exit cases 2021-08-12 09:06:05 -05:00
docs qemu-nbd: Change default cache mode to writeback 2021-09-29 13:46:31 -05:00
dtc@85e5d83984 Makefile: dtc: update, build the libfdt target 2020-06-16 14:49:05 +01:00
dump Do not include cpu.h if it's not really necessary 2021-05-02 17:24:51 +02:00
ebpf ebpf: only include in system emulators 2021-09-17 16:07:52 +08:00
fpu softfloat: Remove assertion preventing silencing of NaN in default-NaN mode 2021-09-01 11:08:17 +01:00
fsdev meson: Declare have_virtfs_proxy_helper in main meson.build 2021-01-23 15:55:04 -05:00
gdb-xml target/riscv: Remove built-in GDB XML files for CSRs 2021-01-16 10:57:21 -08:00
hw hw/loader: Restrict PC_ROM_* definitions to hw/i386/pc 2021-09-27 10:57:21 +02:00
include block: use int64_t instead of int in driver write_zeroes handlers 2021-09-29 13:46:32 -05:00
io io: use GDateTime for formatting timestamp for websock headers 2021-07-14 14:15:52 +01:00
libdecnumber qemu/: fix some comment spelling errors 2020-09-17 20:35:43 +02:00
linux-headers linux-headers: Update 2021-07-09 11:01:06 +10:00
linux-user linux-user/aarch64: Use force_sig_fault() 2021-09-23 14:43:58 +02:00
meson@776acd2a80 submodules: bump meson to 0.55.3 2020-10-17 10:45:42 -04:00
migration migration: Handle migration_incoming_setup() errors consistently 2021-08-26 17:15:28 +02:00
monitor QAPI patches patches for 2021-09-25 2021-09-27 15:03:42 +01:00
nbd nbd/server: Mark variable unused in nbd_negotiate_meta_queries 2021-07-26 07:06:25 -10:00
net vhost-vdpa: remove the unncessary queue_index assignment 2021-09-04 17:34:05 -04:00
pc-bios meson: look up cp and dtrace with find_program() 2021-09-13 13:56:26 +02:00
plugins plugins/api: added a boolean parsing plugin api 2021-09-02 11:29:34 +01:00
po configure: move gettext detection to meson.build 2021-01-02 21:03:09 +01:00
python python/aqmp-tui: Add syntax highlighting 2021-09-27 12:10:29 -04:00
qapi qapi: Convert simple union TransactionAction to flat one 2021-09-27 08:23:25 +02:00
qga Remove superfluous ERRP_GUARD() 2021-08-26 17:15:28 +02:00
qobject qobject: braces {} are necessary for all arms of this statement 2021-02-04 13:20:29 +01:00
qom qom: use correct field name when getting/setting alias properties 2021-07-23 18:17:17 +02:00
replay replay: notify CPU on event 2021-04-01 10:37:20 +02:00
roms Update OpenBIOS images to d657b653 built from submodule. 2021-09-08 10:30:10 +01:00
scripts qapi: Drop simple unions 2021-09-27 08:23:25 +02:00
scsi error: Use error_fatal to simplify obvious fatal errors (again) 2021-08-26 17:15:28 +02:00
semihosting linux-user: Don't include gdbstub.h in qemu.h 2021-09-13 20:35:45 +02:00
slirp@a88d9ace23 Update libslirp to v4.6.1 2021-08-03 16:07:22 +04:00
softmmu qdev: Support marking individual buses as 'full' 2021-09-13 21:01:08 +01:00
storage-daemon storage-daemon: Add missing build dependency to the vhost-user-blk-test 2021-08-11 13:39:50 +02:00
stubs hw/pci: remove all references to find_i440fx function 2021-09-04 17:34:05 -04:00
subprojects/libvhost-user libvhost-user: fix -Werror=format= warnings with __u64 fields 2021-07-29 10:15:52 +02:00
target hw/core: Make do_unaligned_access noreturn 2021-09-21 19:36:44 -07:00
tcg tcg/riscv: Remove add with zero on user-only memory access 2021-09-21 19:36:44 -07:00
tests block: use int64_t instead of uint64_t in driver write handlers 2021-09-29 13:46:31 -05:00
tools virtiofsd pull 2021-08-16 2021-09-19 18:53:29 +01:00
trace meson: look up cp and dtrace with find_program() 2021-09-13 13:56:26 +02:00
ui ui/gtk-egl: Wait for the draw signal for dmabuf blobs 2021-09-15 08:41:59 +02:00
util qapi: Convert simple union SocketAddressLegacy to flat one 2021-09-27 08:23:25 +02:00
.cirrus.yml cirrus: delete FreeBSD and macOS jobs 2021-07-14 14:33:53 +01:00
.dir-locals.el Add .dir-locals.el file to configure emacs coding style 2015-10-08 19:46:01 +03:00
.editorconfig .editorconfig: update the automatic mode setting for Emacs 2021-03-10 15:34:11 +00:00
.exrc qemu: add .exrc 2012-09-07 09:02:44 +03:00
.gdbinit .gdbinit: load QEMU sub-commands when gdb starts 2017-06-07 14:38:45 +01:00
.gitattributes maint: Tell git that *.py files should use python diff hunks 2021-02-15 22:13:34 -05:00
.gitignore gitignore: Update with some filetypes 2021-07-23 17:22:15 +01:00
.gitlab-ci.yml docs: Document GitLab custom CI/CD variables 2021-07-29 07:56:01 +02:00
.gitmodules gitmodules: use GitLab repos instead of qemu.org 2021-02-09 20:53:56 +00:00
.gitpublish Add a git-publish configuration file 2018-03-05 09:03:17 +00:00
.mailmap MAINTAINERS: Name and email address change 2021-08-10 16:42:16 +01:00
.patchew.yml scripts/checkpatch: roll diff tweaking into checkpatch itself 2021-06-25 10:08:33 +01:00
.readthedocs.yml readthedocs: build with Python 3.6 2020-10-05 16:30:45 +01:00
.travis.yml hw/usb/ccid: remove references to NSS 2021-07-14 14:33:53 +01:00
block.c block: bdrv_inactivate_recurse(): check for permissions and fix crash 2021-09-15 15:54:07 +02:00
blockdev-nbd.c block/nbd: Use qcrypto_tls_creds_check_endpoint() 2021-06-29 18:29:47 +01:00
blockdev.c arch_init.h: Don't include arch_init.h unnecessarily 2021-08-26 17:02:00 +01:00
blockjob.c progressmeter: protect with a mutex 2021-06-25 14:24:24 +03:00
configure configure: add missing pc-bios/qemu_vga.ndrv symlink in build tree 2021-09-15 15:54:02 +02:00
COPYING
COPYING.LIB COPYING.LIB: Synchronize the LGPL 2.1 with the version from gnu.org 2019-01-30 11:01:22 +01:00
cpu.c accel/tcg: Record singlestep_enabled in tb->cflags 2021-07-21 07:47:05 -10:00
cpus-common.c overall/alpha tcg cpus|hppa: Fix Lesser GPL version number 2020-11-15 16:43:54 +01:00
disas.c Do not include cpu.h if it's not really necessary 2021-05-02 17:24:51 +02:00
gdbstub.c linux-user: Don't include gdbstub.h in qemu.h 2021-09-13 20:35:45 +02:00
gitdm.config contrib/gitdm: add a new interns group-map for GSoC/Outreachy work 2021-07-23 17:22:16 +01:00
hmp-commands-info.hx monitor/tcg: move tcg hmp commands to accel/tcg, register them dynamically 2021-07-09 18:21:33 +02:00
hmp-commands.hx hmp: Drop a bogus sentence from set_password's documentation 2021-09-27 10:57:21 +02:00
iothread.c iothread: add aio-max-batch parameter 2021-07-21 13:47:50 +01:00
job-qmp.c progressmeter: protect with a mutex 2021-06-25 14:24:24 +03:00
job.c progressmeter: protect with a mutex 2021-06-25 14:24:24 +03:00
Kconfig meson: Introduce target-specific Kconfig 2021-07-09 18:21:34 +02:00
Kconfig.host multi-process: Add config option for multi-process QEMU 2021-02-09 20:53:56 +00:00
LICENSE tcg/LICENSE: Remove out of date claim about TCG subdirectory licensing 2019-11-11 15:11:21 +01:00
MAINTAINERS qemu: Split machine_ppc.py acceptance tests 2021-09-27 19:06:47 +02:00
Makefile Makefile: ignore long options 2021-07-29 10:15:51 +02:00
memory_ldst.c.inc exec/memory_ldst: Use correct type sizes 2021-05-26 08:35:51 -07:00
meson_options.txt configure, meson: convert libxml2 detection to meson 2021-07-06 08:33:51 +02:00
meson.build arm: Add Hypervisor.framework build target 2021-09-21 16:28:26 +01:00
module-common.c all: Clean up includes 2016-02-04 17:41:30 +00:00
os-posix.c remove qemu-options* from root directory 2021-05-26 14:49:46 +02:00
os-win32.c remove qemu-options* from root directory 2021-05-26 14:49:46 +02:00
page-vary-common.c exec: Build page-vary-common.c with -fno-lto 2021-03-23 19:36:47 -06:00
page-vary.c exec: Build page-vary-common.c with -fno-lto 2021-03-23 19:36:47 -06:00
qemu-bridge-helper.c qemu-bridge-helper: relocate path to default ACL 2020-09-30 19:11:36 +02:00
qemu-edid.c qemu-edid: use qemu_edid_size() 2021-05-10 11:41:02 +02:00
qemu-img-cmds.hx qemu-img: Add -F shorthand to convert 2021-09-15 18:42:38 +02:00
qemu-img.c qemu-img: Add -F shorthand to convert 2021-09-15 18:42:38 +02:00
qemu-io-cmds.c block: Acquire AioContexts during bdrv_reopen_multiple() 2021-07-09 13:19:11 +02:00
qemu-io.c error: Use error_fatal to simplify obvious fatal errors (again) 2021-08-26 17:15:28 +02:00
qemu-keymap.c Include qemu-common.h exactly where needed 2019-06-12 13:20:20 +02:00
qemu-nbd.c qemu-nbd: Change default cache mode to writeback 2021-09-29 13:46:31 -05:00
qemu-options.hx softmmu/vl: Deprecate the old grab options 2021-09-06 10:00:14 +02:00
qemu.nsi nsis: adjust for new MinGW paths 2021-01-23 15:55:05 -05:00
qemu.sasl sasl: remove comment about obsolete kerberos versions 2021-06-14 13:28:50 +01:00
README.rst Update documentation to refer to new location for issues 2021-06-21 05:43:11 +02:00
replication.c replication: move include out of root directory 2021-05-26 14:49:46 +02:00
thunk.c linux-user: Drop unneeded includes from qemu.h 2021-09-13 20:35:45 +02:00
trace-events cpu: Add breakpoint tracepoints 2021-07-09 21:31:11 -07:00
VERSION Open 6.2 development tree 2021-08-25 10:25:12 +01:00
version.rc configure: remove CONFIG_FILEVERSION and CONFIG_PRODUCTVERSION 2021-01-02 21:03:37 +01:00

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


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://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.

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