The vhost-user specification does not explain when
VHOST_USER_PROTOCOL_F_MQ must be implemented. This may lead
implementors of vhost-user masters to believe that this protocol feature
is required for any device that has multiple virtqueues. That would be
a mistake since existing vhost-user slaves offer multiple virtqueues but
do not advertise VHOST_USER_PROTOCOL_F_MQ.
For example, a vhost-net device with one rx/tx queue pair is not
multiqueue. The slave does not need to advertise
VHOST_USER_PROTOCOL_F_MQ. Therefore the master must assume it has these
virtqueues and cannot rely on askingt the slave how many virtqueues
exist.
Extend the specification to explain the different between true
multiqueue and regular devices with a fixed virtqueue layout.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20190624091304.666-1-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
The annotated style json we use in QMP documentation is not strict json
and depending on the version of Sphinx (2.0+) or Pygments installed,
might cause the build to fail.
Use the new QMP lexer.
Further, some versions of Sphinx can not apply custom lexers to "code"
directives and require the use of "code-block" directives instead, so
make that change at this time as well.
Tested under:
- Sphinx 1.3.6 and Pygments 2.4
- Sphinx 1.7.6 and Pygments 2.2 (Fedora 29 packages)
- Sphinx 2.0.1 and Pygments 2.4
- Sphinx 3.0.0+/f396b3a783 and Pygments 2.4 (From Sphinx git c4f44bdd)
Reported-by: Aarushi Mehta <mehta.aaru20@gmail.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Message-id: 20190603214653.29369-4-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
The "Multiple queue support" section makes references to vhost-user-net
"queue pairs". This is confusing for two reasons:
1. This actually applies to all device types, not just vhost-user-net.
2. VHOST_USER_GET_QUEUE_NUM returns the number of virtqueues, not the
number of queue pairs.
Reword the section so that the vhost-user-net specific part is relegated
to the very end: we acknowledge that vhost-user-net historically
automatically enabled the first queue pair.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190626074815.19994-5-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Add a new vhost-user message to give a unix socket to a vhost-user
backend for GPU display updates.
Back when I started that work, I added a new GPU channel because the
vhost-user protocol wasn't bidirectional. Since then, there is a
vhost-user-slave channel for the slave to send requests to the master.
We could extend it with GPU messages. However, the GPU protocol is
quite orthogonal to vhost-user, thus I chose to have a new dedicated
channel.
See vhost-user-gpu.rst for the protocol details.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20190524130946.31736-2-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This just about rewrites the entirety of the bitmaps.rst document to
make it consistent with the 4.0 release. I have added new features seen
in the 4.0 release, as well as tried to clarify some points that keep
coming up when discussing this feature both in-house and upstream.
It does not yet cover pull backups or migration details, but I intend to
keep extending this document to cover those cases.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190426221528.30293-3-jsnow@redhat.com
[Adjusted commit message. --js]
Signed-off-by: John Snow <jsnow@redhat.com>
This patch introduces two new messages VHOST_USER_GET_INFLIGHT_FD
and VHOST_USER_SET_INFLIGHT_FD to support transferring a shared
buffer between qemu and backend.
Firstly, qemu uses VHOST_USER_GET_INFLIGHT_FD to get the
shared buffer from backend. Then qemu should send it back
through VHOST_USER_SET_INFLIGHT_FD each time we start vhost-user.
This shared buffer is used to track inflight I/O by backend.
Qemu should retrieve a new one when vm reset.
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Chai Wen <chaiwen@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
Message-Id: <20190228085355.9614-2-xieyongji@baidu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
We already use (we didn't notice it) IN_USE flag for marking bitmap
metadata outdated, such as AUTO flag, which mirrors enabled/disabled
bitmaps. Now we are going to support bitmap resize, so it's good to
write IN_USE meaning with more details.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190311185147.52309-2-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
By default Sphinx wants to build a single manual at once.
For QEMU, this doesn't suit us, because we want to have
separate manuals for "Developer's Guide", "User Manual",
and so on, and we don't want to ship the Developer's Guide
to end-users. However, we don't want to completely duplicate
conf.py for each manual, and we'd like to continue to
support "build all docs in one run" for third-party sites
like readthedocs.org.
Make the top-level conf.py support two usage forms:
(1) as a common config file which is included by the conf.py
for each of QEMU's manuals: in this case sphinx-build is run
multiple times, once per subdirectory.
(2) as a top level conf file which will result in building all
the manuals into a single document: in this case sphinx-build is
run once, on the top-level docs directory.
Provide per-manual conf.py files and top level pages for
our first two manuals:
* QEMU Developer's Guide (docs/devel)
* QEMU System Emulation Management and Interoperability Guide
(docs/interop)
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Message-id: 20190305172139.32662-9-peter.maydell@linaro.org
Message-id: 20190228145624.24885-9-peter.maydell@linaro.org
It can be useful to figure out which NBD protocol features are
exposed by a server, as well as what features a client will
take advantage of if available, for a given qemu release. It's
not always precise to base features on version numbers (thanks
to downstream backports), but any documentation is better than
making users search through git logs themselves.
This patch originally stemmed from a request to document that
pristine 3.0 has a known bug where NBD_OPT_LIST_META_CONTEXT
with 0 queries forgot to advertise an available
"qemu:dirty-bitmap" context, but documenting bugs like this (or
the fact that 3.0 also botched NBD_CMD_CACHE) gets to be too
much details, especially since buggy releases will be less
likely connection targets over time. Instead, I chose to just
remind users to check stable release branches.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181215135324.152629-3-eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
When a QMP client sends in-band commands more quickly that we can
process them, we can either queue them without limit (QUEUE), drop
commands when the queue is full (DROP), or suspend receiving commands
when the queue is full (SUSPEND). None of them is ideal:
* QUEUE lets a misbehaving client make QEMU eat memory without bounds.
Not such a hot idea.
* With DROP, the client has to cope with dropped in-band commands. To
inform the client, we send a COMMAND_DROPPED event then. The event is
flawed by design in two ways: it's ambiguous (see commit d621cfe0a1),
and it brings back the "eat memory without bounds" problem.
* With SUSPEND, the client has to manage the flow of in-band commands to
keep the monitor available for out-of-band commands.
We currently DROP. Switch to SUSPEND.
Managing the flow of in-band commands to keep the monitor available for
out-of-band commands isn't really hard: just count the number of
"outstanding" in-band commands (commands sent minus replies received),
and if it exceeds the limit, hold back additional ones until it drops
below the limit again.
Note that we need to be careful pairing the suspend with a resume, or
else the monitor will hang, possibly forever. And here since we need to
make sure both:
(1) popping request from the req queue, and
(2) reading length of the req queue
will be in the same critical section, we let the pop function take the
corresponding queue lock when there is a request, then we release the
lock from the caller.
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20181009062718.1914-2-peterx@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Although off_t permits up to 63 bits (8EB) of file offsets, in
practice, we're going to hit other limits first. Document some
of those limits in the qcow2 spec (some are inherent, others are
implementation choices of qemu), and how choice of cluster size
can influence some of the limits.
While we cannot map any uncompressed virtual cluster to any
address higher than 64 PB (56 bits) (due to the current L1/L2
field encoding stopping at bit 55), qemu's cap of 8M for the
refcount table can still access larger host addresses for some
combinations of large clusters and small refcount_order. For
comparison, ext4 with 4k blocks caps files at 16PB.
Another interesting limit: for compressed clusters, the L2 layout
requires an ever-smaller maximum host offset as cluster size gets
larger, down to a 512 TB maximum with 2M clusters. In particular,
note that with a cluster size of 8k or smaller, the L2 entry for
a compressed cluster could technically point beyond the 64PB mark,
but when you consider that with 8k clusters and refcount_order = 0,
you cannot access beyond 512T without exceeding qemu's limit of an
8M cap on the refcount table, it is unlikely that any image in the
wild has attempted to do so. To be safe, let's document that bits
beyond 55 in a compressed cluster must be 0.
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
It's the same as -no-user-config and marked as deprecated since three
releases already. Time to remove it now.
Acked-by: Peter Krempa <pkrempa@redhat.com>
Acked-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Section "QGA Synchronization" specifies that sending "a raw 0xFF
sentinel byte" makes the server "reset its state and discard all
pending data prior to the sentinel." What actually happens there is a
lexical error, which will produce one or more error responses.
Moreover, it's not specific to QGA.
Create new section "Forcing the JSON parser into known-good state" to
document the technique properly. Rewrite section "QGA
Synchronization" to document just the other direction, i.e. command
guest-sync-delimited.
Section "Protocol Specification" mentions "synchronization bytes
(documented below)". Delete that.
While there, fix it not to claim '"Server" is QEMU itself', but
'"Server" is either QEMU or the QEMU Guest Agent'.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180823164025.12553-2-armbru@redhat.com>
Stefan HajnocziandMichael S. Tsirkin
John Snow
Marc-André LureauandMichael S. Tsirkin
Peter Maydell
Xie YongjiandMichael S. Tsirkin
Vladimir Sementsov-OgievskiyandJohn Snow
Markus Armbruster
Kevin Wolf
Eric Blake
Peter XuandMarkus Armbruster
Stefan WeilandThomas Huth
Ville SkyttäandPeter Maydell