For vhost-user devices, qemu can migrate the virtio state, but not the
back-end's internal state. To do so, we need to be able to transfer
this internal state between front-end (qemu) and back-end.
At this point, this new feature is added for the purpose of virtio-fs
migration. Because virtiofsd's internal state will not be too large, we
believe it is best to transfer it as a single binary blob after the
streaming phase.
These are the additions to the protocol:
- New vhost-user protocol feature VHOST_USER_PROTOCOL_F_DEVICE_STATE
- SET_DEVICE_STATE_FD function: Front-end and back-end negotiate a file
descriptor over which to transfer the state.
- CHECK_DEVICE_STATE: After the state has been transferred through the
file descriptor, the front-end invokes this function to verify
success. There is no in-band way (through the file descriptor) to
indicate failure, so we need to check explicitly.
Once the transfer FD has been established via SET_DEVICE_STATE_FD
(which includes establishing the direction of transfer and migration
phase), the sending side writes its data into it, and the reading side
reads it until it sees an EOF. Then, the front-end will check for
success via CHECK_DEVICE_STATE, which on the destination side includes
checking for integrity (i.e. errors during deserialization).
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20231016134243.68248-5-hreitz@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
In vDPA, GET_VRING_BASE does not stop the queried vring, which is why
SUSPEND was introduced so that the returned index would be stable. In
vhost-user, it does stop the vring, so under the same reasoning, it can
get away without SUSPEND.
Still, we do want to clarify that if the device is completely stopped,
i.e. all vrings are stopped, the back-end should cease to modify any
state relating to the guest. Do this by calling it "suspended".
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20231016134243.68248-4-hreitz@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Currently, the vhost-user documentation says that rings are to be
initialized in a disabled state when VHOST_USER_F_PROTOCOL_FEATURES is
negotiated. However, by the time of feature negotiation, all rings have
already been initialized, so it is not entirely clear what this means.
At least the vhost-user-backend Rust crate's implementation interpreted
it to mean that whenever this feature is negotiated, all rings are to
put into a disabled state, which means that every SET_FEATURES call
would disable all rings, effectively halting the device. This is
problematic because the VHOST_F_LOG_ALL feature is also set or cleared
this way, which happens during migration. Doing so should not halt the
device.
Other implementations have interpreted this to mean that the device is
to be initialized with all rings disabled, and a subsequent SET_FEATURES
call that does not set VHOST_USER_F_PROTOCOL_FEATURES will enable all of
them. Here, SET_FEATURES will never disable any ring.
This interpretation does not suffer the problem of unintentionally
halting the device whenever features are set or cleared, so it seems
better and more reasonable.
We can clarify this in the documentation by making it explicit that the
enabled/disabled state is tracked even while the vring is stopped.
Every vring is initialized in a disabled state, and SET_FEATURES without
VHOST_USER_F_PROTOCOL_FEATURES simply becomes one way to enable all
vrings.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20231016134243.68248-3-hreitz@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
GET_VRING_BASE does not mention that it stops the respective ring. Fix
that.
Furthermore, it is not fully clear what the "base offset" these
commands' documentation refers to is; an offset could be many things.
Be more precise and verbose about it, especially given that these
commands use different payload structures depending on whether the vring
is split or packed.
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20231016134243.68248-2-hreitz@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The VHOST_USER_PROTOCOL_F_XEN_MMAP feature bit was defined in
f21e95ee97, which has been part of qemu's 8.1.0 release. However, it
seems it was never added to qemu's code, but it is well possible that it
is already used by different front-ends outside of qemu (i.e., Xen).
VHOST_USER_PROTOCOL_F_SHARED_OBJECT in contrast was added to qemu's code
in 1609476662, but never defined in the vhost-user specification. As a
consequence, both bits were defined to be 17, which cannot work.
Regardless of whether actual code or the specification should take
precedence, F_XEN_MMAP is already part of a qemu release, while
F_SHARED_OBJECT is not. Therefore, bump the latter to take number 18
instead of 17, and add this to the specification.
Take the opportunity to add at least a little note on the
VhostUserShared structure to the specification. This structure is
referenced by the new commands introduced in 1609476662, but was not
defined.
Fixes: 1609476662
("vhost-user: add shared_object msg")
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20231016083201.23736-1-hreitz@redhat.com>
Reviewed-by: Emmanouil Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Allow a client to request a subset of negotiated meta contexts. For
example, a client may ask to use a single connection to learn about
both block status and dirty bitmaps, but where the dirty bitmap
queries only need to be performed on a subset of the disk; forcing the
server to compute that information on block status queries in the rest
of the disk is wasted effort (both at the server, and on the amount of
traffic sent over the wire to be parsed and ignored by the client).
Qemu as an NBD client never requests to use more than one meta
context, so it has no need to use block status payloads. Testing this
instead requires support from libnbd, which CAN access multiple meta
contexts in parallel from a single NBD connection; an interop test
submitted to the libnbd project at the same time as this patch
demonstrates the feature working, as well as testing some corner cases
(for example, when the payload length is longer than the export
length), although other corner cases (like passing the same id
duplicated) requires a protocol fuzzer because libnbd is not wired up
to break the protocol that badly.
This also includes tweaks to 'qemu-nbd --list' to show when a server
is advertising the capability, and to the testsuite to reflect the
addition to that output.
Of note: qemu will always advertise the new feature bit during
NBD_OPT_INFO if extended headers have alreay been negotiated
(regardless of whether any NBD_OPT_SET_META_CONTEXT negotiation has
occurred); but for NBD_OPT_GO, qemu only advertises the feature if
block status is also enabled (that is, if the client does not
negotiate any contexts, then NBD_CMD_BLOCK_STATUS cannot be used, so
the feature is not advertised).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20230925192229.3186470-26-eblake@redhat.com>
[eblake: fix logic to reject unnegotiated contexts]
Signed-off-by: Eric Blake <eblake@redhat.com>
Time to start supporting clients that request extended headers. Now
we can finally reach the code added across several previous patches.
Even though the NBD spec has been altered to allow us to accept
NBD_CMD_READ larger than the max payload size (provided our response
is a hole or broken up over more than one data chunk), we are not
planning to take advantage of that, and continue to cap NBD_CMD_READ
to 32M regardless of header size.
For NBD_CMD_WRITE_ZEROES and NBD_CMD_TRIM, the block layer already
supports 64-bit operations without any effort on our part. For
NBD_CMD_BLOCK_STATUS, the client's length is a hint, and the previous
patch took care of implementing the required
NBD_REPLY_TYPE_BLOCK_STATUS_EXT.
We do not yet support clients that want to do request payload
filtering of NBD_CMD_BLOCK_STATUS; that will be added in later
patches, but is not essential for qemu as a client since qemu only
requests the single context base:allocation.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230925192229.3186470-19-eblake@redhat.com>
Add three new vhost-user protocol
`VHOST_USER_BACKEND_SHARED_OBJECT_* messages`.
These new messages are sent from vhost-user
back-ends to interact with the virtio-dmabuf
table in order to add or remove themselves as
virtio exporters, or lookup for virtio dma-buf
shared objects.
The action taken in the front-end depends
on the type stored in the virtio shared
object hash table.
When the table holds a pointer to a vhost
backend for a given UUID, the front-end sends
a VHOST_USER_GET_SHARED_OBJECT to the
backend holding the shared object.
The messages can only be sent after successfully
negotiating a new VHOST_USER_PROTOCOL_F_SHARED_OBJECT
vhost-user protocol feature bit.
Finally, refactor code to send response message so
that all common parts both for the common REPLY_ACK
case, and other data responses, can call it and
avoid code repetition.
Signed-off-by: Albert Esteve <aesteve@redhat.com>
Message-Id: <20231002065706.94707-4-aesteve@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
VHOST_USER_GPU_DMABUF_SCANOUT2 is defined as a message with all the
contents of VHOST_USER_GPU_DMABUF_SCANOUT plus the dmabuf modifiers
which were ommitted.
The VHOST_USER_GPU_PROTOCOL_F_DMABUF2 protocol feature is defined as a
way to check whether this new message is supported or not.
Signed-off-by: Erico Nunes <ernunes@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20230714153900.475857-2-ernunes@redhat.com>
vhost-user-gpu: edid
vhost-user-scmi device
vhost-vdpa: _F_CTRL_RX and _F_CTRL_RX_EXTRA support for svq
cleanups, fixes all over the place.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Merge tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu into staging
pc,pci,virtio: cleanups, fixes, features
vhost-user-gpu: edid
vhost-user-scmi device
vhost-vdpa: _F_CTRL_RX and _F_CTRL_RX_EXTRA support for svq
cleanups, fixes all over the place.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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* tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu: (66 commits)
vdpa: Allow VIRTIO_NET_F_CTRL_RX_EXTRA in SVQ
vdpa: Restore packet receive filtering state relative with _F_CTRL_RX_EXTRA feature
vdpa: Allow VIRTIO_NET_F_CTRL_RX in SVQ
vdpa: Avoid forwarding large CVQ command failures
vdpa: Accessing CVQ header through its structure
vhost: Fix false positive out-of-bounds
vdpa: Restore packet receive filtering state relative with _F_CTRL_RX feature
vdpa: Restore MAC address filtering state
vdpa: Use iovec for vhost_vdpa_net_load_cmd()
pcie: Specify 0 for ARI next function numbers
pcie: Use common ARI next function number
include/hw/virtio: document some more usage of notifiers
include/hw/virtio: add kerneldoc for virtio_init
include/hw/virtio: document virtio_notify_config
hw/virtio: fix typo in VIRTIO_CONFIG_IRQ_IDX comments
include/hw: document the device_class_set_parent_* fns
include: attempt to document device_class_set_props
vdpa: Fix possible use-after-free for VirtQueueElement
pcie: Add hotplug detect state register to cmask
virtio-iommu: Rework the traces in virtio_iommu_set_page_size_mask()
...
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
VHOST_USER_GPU_GET_EDID is defined as a message from the backend to the
frontend to retrieve the EDID data for a given scanout.
The VHOST_USER_GPU_PROTOCOL_F_EDID protocol feature is defined as a way
to check whether this new message is supported or not.
Signed-off-by: Erico Nunes <ernunes@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230626164708.1163239-3-ernunes@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The allow-rpcs option accepts a comma-separated list of RPCs to
enable. This option is opposite to --block-rpcs. Using --block-rpcs
and --allow-rpcs at the same time is not allowed.
resolves: https://gitlab.com/qemu-project/qemu/-/issues/1505
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Although we already covered the need for padding bytes with our
changes in commit 3ae3fcfa, commit 66fcbca5 (both v5.0.0) added one
byte and relied on the rest of the text for implicitly covering 7
padding bytes. For consistency with other parts of the header (such
as the header extension format listing padding from n - m, or the
snapshot table entry listing variable padding), we might as well call
out the remaining 7 bytes as padding until such time (as any) as they
gain another meaning.
Signed-off-by: Eric Blake <eblake@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20230522184631.47211-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
qmp-intro.txt is quite small and provides very little information
that isn't already in the documentation elsewhere. Fold the example
command lines into qemu-options.hx, and delete the now-unneeded plain
text document.
While we're touching the qemu-options.hx documentation text,
wordsmith it a little bit and improve the rST formatting.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20230515162245.3964307-4-peter.maydell@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
The description text for a parsing error has changed since the
spec doc was first written; update the example in the docs.
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20230515162245.3964307-3-peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Convert the qmp-spec.txt document to restructuredText.
Notable points about the conversion:
* numbers at the start of section headings are removed, to match
the style of the rest of the manual
* cross-references to other sections or documents are hyperlinked
* various formatting tweaks (notably the examples, which need the
-> and <- prefixed so the QMP code-block lexer will accept them)
* English prose fixed in a few places
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20230515162245.3964307-2-peter.maydell@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
[.. code-block:: dumbed down to :: to work around CI failure]
"zlib" clusters are actually raw deflate (RFC1951) clusters without
zlib headers.
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
Message-Id: <168424874322.11954.1340942046351859521-0@git.sr.ht>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Documentation suggests @foo is merely shorthand for ``foo``. It's
not, it carries additional meaning: it's a reference to a QAPI schema
name.
Reword the documentation to spell that out.
Fix up the few ``foo`` that should be @foo.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230425064223.820979-7-armbru@redhat.com>
The current model of memory mapping at the back-end works fine where a
standard call to mmap() (for the respective file descriptor) is enough
before the front-end can start accessing the guest memory.
There are other complex cases though where the back-end needs more
information and simple mmap() isn't enough. For example Xen, a type-1
hypervisor, currently supports memory mapping via two different methods,
foreign-mapping (via /dev/privcmd) and grant-dev (via /dev/gntdev). In
both these cases, the back-end needs to call mmap() and ioctl(), with
extra information like the Xen domain-id of the guest whose memory we
are trying to map.
Add a new protocol feature, 'VHOST_USER_PROTOCOL_F_XEN_MMAP', which lets
the back-end know about the additional memory mapping requirements.
When this feature is negotiated, the front-end will send the additional
information within the memory regions themselves.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-Id: <6d0bd7f0e1aeec3ddb603ae4ff334c75c7d0d7b3.1678351495.git.viresh.kumar@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
The same layout is defined twice, once in "single memory region
description" and then in "memory regions description".
Separate out details of memory region from these two and reuse the same
definition later on.
While at it, also rename "memory regions description" to "multiple
memory regions description", to avoid potential confusion around similar
names. And define single region before multiple ones.
This is just a documentation optimization, the protocol remains the same.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-Id: <7c3718e5eb99178b22696682ae73aca6df1899c7.1678351495.git.viresh.kumar@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Backend's message and protocol features names were still
using "_SLAVE_" naming. For consistency with the new naming
convention, replace it with _BACKEND_.
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Message-Id: <20230208203259.381326-2-maxime.coquelin@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Drop the frankly misleading quickstart section for a more rounded
introduction section. This new section gives an overview of the
accelerators as well as a high level introduction to some of the key
features of the emulator. We also expand on a general form for a QEMU
command line with a hopefully not too scary worked example of what
this looks like.
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
Message-Id: <20230124180127.1881110-23-alex.bennee@linaro.org>
The file seems to contain perfectly valid rst syntax already, so
rename it to .rst and wire it up in the index.
Message-Id: <20221213101806.46640-1-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Add new firmware feature flags for the recently added confidential
computing operating modes by amd and intel.
While being at it also fix the path to the amd sev documentation.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
Message-Id: <20220930133220.1771336-1-kraxel@redhat.com>
Let's use a more appropriate wording for this command line and config
file option. The old ones are still accepted for compatibility reasons,
but marked as deprecated now so that it could be removed in a future
version of QEMU.
This change is based on earlier patches from Philippe Mathieu-Daudé,
with the idea for the new option name suggested by BALATON Zoltan.
And while we're at it, replace the "?" in the help text with "help"
since that does not have the problem of conflicting with the wildcard
character of the shells.
Message-Id: <20220727092135.302915-2-thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220707163720.1421716-5-berrange@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This reverts commit 76b1b64370.
The commit only duplicated some text that had already been merged in
commit 31009d13cc.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220627134500.94842-2-kwolf@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
We have about 30 instances of the typo/variant spelling 'writeable',
and over 500 of the more common 'writable'. Standardize on the
latter.
Change produced with:
sed -i -e 's/\([Ww][Rr][Ii][Tt]\)[Ee]\([Aa][Bb][Ll][Ee]\)/\1\2/g' $(git grep -il writeable)
and then hand-undoing the instance in linux-headers/linux/kvm.h.
Most of these changes are in comments or documentation; the
exceptions are:
* a local variable in accel/hvf/hvf-accel-ops.c
* a local variable in accel/kvm/kvm-all.c
* the PMCR_WRITABLE_MASK macro in target/arm/internals.h
* the EPT_VIOLATION_GPA_WRITABLE macro in target/i386/hvf/vmcs.h
(which is never used anywhere)
* the AR_TYPE_WRITABLE_MASK macro in target/i386/hvf/vmx.h
(which is never used anywhere)
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Message-id: 20220505095015.2714666-1-peter.maydell@linaro.org
The specification for VHOST_USER_ADD/REM_MEM_REG messages is unclear
in several points, which has led to clients having incompatible
implementations. This changes the specification to be more explicit
about them:
* VHOST_USER_ADD_MEM_REG is not specified as receiving a file
descriptor, though it obviously does need to do so. All
implementations agree on this one, fix the specification.
* VHOST_USER_REM_MEM_REG is not specified as receiving a file
descriptor either, and it also has no reason to do so. rust-vmm does
not send file descriptors for removing a memory region (in agreement
with the specification), libvhost-user and QEMU do (which is a bug),
though libvhost-user doesn't actually make any use of it.
Change the specification so that for compatibility QEMU's behaviour
becomes legal, even if discouraged, but rust-vmm's behaviour becomes
the explicitly recommended mode of operation.
* VHOST_USER_ADD_MEM_REG doesn't have a documented return value, which
is the desired behaviour in the non-postcopy case. It also implemented
like this in QEMU and rust-vmm, though libvhost-user is buggy and
sometimes sends an unexpected reply. This will be fixed in a separate
patch.
However, in postcopy mode it does reply like VHOST_USER_SET_MEM_TABLE.
This behaviour is shared between libvhost-user and QEMU; rust-vmm
doesn't implement postcopy mode yet. Mention it explicitly in the
spec.
* The specification doesn't mention how VHOST_USER_REM_MEM_REG
identifies the memory region to be removed. Change it to describe the
existing behaviour of libvhost-user (guest address, user address and
size must match).
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220407133657.155281-2-kwolf@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Make the language about feature negotiation explicitly clear about the
handling of the VHOST_USER_F_PROTOCOL_FEATURES feature bit. Try and
avoid the sort of bug introduced in vhost.rs REPLY_ACK processing:
https://github.com/rust-vmm/vhost/pull/24
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Jiang Liu <gerry@linux.alibaba.com>
Message-Id: <20210226111619.21178-1-alex.bennee@linaro.org>
Message-Id: <20220321153037.3622127-8-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This matches the nomenclature that is generally used. Also commonly used
is client/server, but it is not as clear because sometimes the front-end
exposes a passive (server) socket that the back-end connects to.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210226143413.188046-4-pbonzini@redhat.com>
Message-Id: <20220321153037.3622127-7-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This section is using the word "back-end" to refer to the
"slave's back-end", and talking about the "client" for
what the rest of the document calls the "slave".
Rework it to free the use of the term "back-end", which in
the next patch will replace "slave".
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210226143413.188046-3-pbonzini@redhat.com>
Message-Id: <20220321153037.3622127-6-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
It is not necessary to mention which side is sending/receiving
each payload; it is more interesting to say which is the request
and which is the reply. This also matches what vhost-user-gpu.rst
already does.
While at it, ensure that all messages list both the request and
the reply payload.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210226143413.188046-2-pbonzini@redhat.com>
Message-Id: <20220321153037.3622127-5-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
According to the NBD spec, a server that advertises
NBD_FLAG_CAN_MULTI_CONN promises that multiple client connections will
not see any cache inconsistencies: when properly separated by a single
flush, actions performed by one client will be visible to another
client, regardless of which client did the flush.
We always satisfy these conditions in qemu - even when we support
multiple clients, ALL clients go through a single point of reference
into the block layer, with no local caching. The effect of one client
is instantly visible to the next client. Even if our backend were a
network device, we argue that any multi-path caching effects that
would cause inconsistencies in back-to-back actions not seeing the
effect of previous actions would be a bug in that backend, and not the
fault of caching in qemu. As such, it is safe to unconditionally
advertise CAN_MULTI_CONN for any qemu NBD server situation that
supports parallel clients.
Note, however, that we don't want to advertise CAN_MULTI_CONN when we
know that a second client cannot connect (for historical reasons,
qemu-nbd defaults to a single connection while nbd-server-add and QMP
commands default to unlimited connections; but we already have
existing means to let either style of NBD server creation alter those
defaults). This is visible by no longer advertising MULTI_CONN for
'qemu-nbd -r' without -e, as in the iotest nbd-qemu-allocation.
The harder part of this patch is setting up an iotest to demonstrate
behavior of multiple NBD clients to a single server. It might be
possible with parallel qemu-io processes, but I found it easier to do
in python with the help of libnbd, and help from Nir and Vladimir in
writing the test.
Signed-off-by: Eric Blake <eblake@redhat.com>
Suggested-by: Nir Soffer <nsoffer@redhat.com>
Suggested-by: Vladimir Sementsov-Ogievskiy <v.sementsov-og@mail.ru>
Message-Id: <20220512004924.417153-3-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The specification for VHOST_USER_ADD/REM_MEM_REG messages is unclear
in several points, which has led to clients having incompatible
implementations. This changes the specification to be more explicit
about them:
* VHOST_USER_ADD_MEM_REG is not specified as receiving a file
descriptor, though it obviously does need to do so. All
implementations agree on this one, fix the specification.
* VHOST_USER_REM_MEM_REG is not specified as receiving a file
descriptor either, and it also has no reason to do so. rust-vmm does
not send file descriptors for removing a memory region (in agreement
with the specification), libvhost-user and QEMU do (which is a bug),
though libvhost-user doesn't actually make any use of it.
Change the specification so that for compatibility QEMU's behaviour
becomes legal, even if discouraged, but rust-vmm's behaviour becomes
the explicitly recommended mode of operation.
* VHOST_USER_ADD_MEM_REG doesn't have a documented return value, which
is the desired behaviour in the non-postcopy case. It also implemented
like this in QEMU and rust-vmm, though libvhost-user is buggy and
sometimes sends an unexpected reply. This will be fixed in a separate
patch.
However, in postcopy mode it does reply like VHOST_USER_SET_MEM_TABLE.
This behaviour is shared between libvhost-user and QEMU; rust-vmm
doesn't implement postcopy mode yet. Mention it explicitly in the
spec.
* The specification doesn't mention how VHOST_USER_REM_MEM_REG
identifies the memory region to be removed. Change it to describe the
existing behaviour of libvhost-user (guest address, user address and
size must match).
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220407133657.155281-2-kwolf@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Add a section explaining how vhost-user is supported on platforms
other than Linux.
Signed-off-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220304100854.14829-5-slp@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The current firmware descriptor schema for flash requires that both the
executable to NVRAM template paths be provided. This is fine for the
most common usage of EDK2 builds in virtualization where the separate
_CODE and _VARS files are provided.
With confidential computing technology like AMD SEV, persistent storage
of variables may be completely disabled because the firmware requires a
known clean state on every cold boot. There is no way to express this
in the firmware descriptor today.
Even with regular EDK2 builds it is possible to create a firmware that
has both executable code and variable persistence in a single file. This
hasn't been commonly used, since it would mean every guest bootup would
need to clone the full firmware file, leading to redundant duplicate
storage of the code portion. In some scenarios this may not matter and
might even be beneficial. For example if a public cloud allows users to
bring their own firmware, such that the user can pre-enroll their own
secure boot keys, you're going to have this copied on disk for each
tenant already. At this point the it can be simpler to just deal with
a single file rather than split builds. The firmware descriptor ought
to be able to express this combined firmware model too.
This all points towards expanding the schema for flash with a 'mode'
concept:
- "split" - the current implicit behaviour with separate files
for code and variables.
- "combined" - the alternate behaviour where a single file contains
both code and variables.
- "stateless" - the confidential computing use case where storage
of variables is completely disable, leaving only the code.
Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
The virtio-balloon-stats documentation might be useful for people that
are implementing software that talks to QEMU via QMP, so this should
reside in the docs/interop/ directory. While we're at it, also convert
the file to restructured text and mention it in the MAINTAINERS file.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220105115245.420945-1-thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Wire up the dbus-display documentation. The interface and feature is
implemented next.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Use the source XML document as single reference, importing its
documentation via the dbus-doc directive.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Modern way is using blockdev-add + blockdev-backup, which provides a
lot more control on how target is opened.
As example of drive-backup problems consider the following:
User of drive-backup expects that target will be opened in the same
cache and aio mode as source. Corresponding logic is in
drive_backup_prepare(), where we take bs->open_flags of source.
It works rather bad if source was added by blockdev-add. Assume source
is qcow2 image. On blockdev-add we should specify aio and cache options
for file child of qcow2 node. What happens next:
drive_backup_prepare() looks at bs->open_flags of qcow2 source node.
But there no BDRV_O_NOCAHE neither BDRV_O_NATIVE_AIO: BDRV_O_NOCAHE is
places in bs->file->bs->open_flags, and BDRV_O_NATIVE_AIO is nowhere,
as file-posix parse options and simply set s->use_linux_aio.
The documentation is updated in a minimal way, so that drive-backup is
noted only as a deprecated command, and blockdev-backup used in most of
places.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
We are going to deprecate drive-backup, so use modern interface here.
In examples where target image creation is shown, show blockdev-add as
well. If target creation omitted, omit blockdev-add as well.
Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
The single backtick markup in ReST is the "default role". Currently,
Sphinx's default role is called "content". Sphinx suggests you can use
the "Any" role instead to turn any single-backtick enclosed item into a
cross-reference.
This is useful for things like autodoc for Python docstrings, where it's
often nicer to reference other types with `foo` instead of the more
laborious :py:meth:`foo`. It's also useful in multi-domain cases to
easily reference definitions from other Sphinx domains, such as
referencing C code definitions from outside of kerneldoc comments.
Before we do that, though, we'll need to turn all existing usages of the
"content" role to inline verbatim markup wherever it does not correctly
resolve into a cross-refernece by using double backticks instead.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20211004215238.1523082-2-jsnow@redhat.com>
Use a standard heading format for the index.rst file in a directory.
Using overlines makes it clear that individual documents can use e.g.
=== for chapter titles and --- for section titles, as suggested in the
Linux kernel guidelines[1]. They could do it anyway, because documents
included in a toctree are parsed separately and therefore are not tied
to the same conventions for headings. However, keeping some consistency is
useful since sometimes files are included from multiple places.
[1] https://www.kernel.org/doc/html/latest/doc-guide/sphinx.html
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Most of docs/barrier.txt is describing the protocol implemented
by the input-barrier device. Move this into the interop
section of the manual, and rstify it.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-id: 20210727204112.12579-2-peter.maydell@linaro.org
In rST markup, single backticks `like this` represent "interpreted
text", which can be handled as a bunch of different things if tagged
with a specific "role":
https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#interpreted-text
(the most common one for us is "reference to a URL, which gets
hyperlinked").
The default "role" if none is specified is "title_reference",
intended for references to book or article titles, and it renders
into the HTML as <cite>...</cite> (usually comes out as italics).
This commit fixes various places in the manual which were
using single backticks when double backticks (for literal text)
were intended, and covers those files where only one or two
instances of these errors were made.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Our built HTML documentation now has a standard footer which
gives the license for QEMU (and its documentation as a whole).
In almost all pages, we either don't bother to state the
copyright/license for the individual rST sources, or we put
it in an rST comment. There are just three pages which render
copyright or license information into the user-visible HTML.
Quoting a specific (different) license for an individual HTML
page within the manual is confusing. Downgrade the license
and copyright info to a comment within the rST source, bringing
these pages in line with the rest of our documents.
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-id: 20210722192016.24915-3-peter.maydell@linaro.org
