aboutsummaryrefslogtreecommitdiff
path: root/docs/interop/vhost-user.rst
AgeCommit message (Collapse)Author
2023-11-07vhost-user.rst: Migrating back-end-internal stateHanna Czenczek
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>
2023-11-07vhost-user.rst: Introduce suspended stateHanna Czenczek
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>
2023-11-07vhost-user.rst: Clarify enabling/disabling vringsHanna Czenczek
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>
2023-11-07vhost-user.rst: Improve [GS]ET_VRING_BASE docHanna Czenczek
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>
2023-10-22vhost-user: Fix protocol feature bit conflictHanna Czenczek
The VHOST_USER_PROTOCOL_F_XEN_MMAP feature bit was defined in f21e95ee97d, 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 16094766627, 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 16094766627, but was not defined. Fixes: 160947666276c5b7f6bca4d746bcac2966635d79 ("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>
2023-10-04vhost-user: add shared_object msgAlbert Esteve
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>
2023-04-21docs: vhost-user: Add Xen specific memory mapping supportViresh Kumar
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>
2023-04-21docs: vhost-user: Define memory region separatelyViresh Kumar
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>
2023-03-02docs: vhost-user: replace _SLAVE_ with _BACKEND_Maxime Coquelin
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>
2022-06-27docs/vhost-user: Fix mismergeKevin Wolf
This reverts commit 76b1b64370007234279ea4cc8b09c98cbd2523de. The commit only duplicated some text that had already been merged in commit 31009d13cc5. 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>
2022-06-08Fix 'writeable' typosPeter Maydell
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
2022-05-16docs/vhost-user: Clarifications for VHOST_USER_ADD/REM_MEM_REGKevin Wolf
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>
2022-05-16vhost-user: more master/slave thingsMichael S. Tsirkin
we switched to front-end/back-end, but newer patches reintroduced old language. Fix this up. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-05-16vhost-user.rst: add clarifying language about protocol negotiationAlex Bennée
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>
2022-05-16docs: vhost-user: replace master/slave with front-end/back-endPaolo Bonzini
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>
2022-05-16docs: vhost-user: rewrite section on ring state machinePaolo Bonzini
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>
2022-05-16docs: vhost-user: clean up request/reply descriptionPaolo Bonzini
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>
2022-05-04docs/vhost-user: Clarifications for VHOST_USER_ADD/REM_MEM_REGKevin Wolf
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>
2022-03-06docs: vhost-user: add subsection for non-Linux platformsSergio Lopez
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>
2021-08-02docs: Move licence/copyright from HTML output to rST commentsPeter Maydell
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
2021-07-23docs: add a section on the generalities of vhost-userAlex Bennée
While we do mention some of this stuff in the various daemons and manuals the subtleties of the socket and memory sharing are sometimes missed. This document attempts to give some background on vhost-user daemons in general terms. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20210720232703.10650-4-alex.bennee@linaro.org>
2020-11-18docs: Fix some typos (found by codespell)Stefan Weil
Fix also a similar typo in a code comment. Signed-off-by: Stefan Weil <sw@weilnetz.de> Message-Id: <20201117193448.393472-1-sw@weilnetz.de> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-11-12vhost-user: fix VHOST_USER_ADD/REM_MEM_REG truncationStefan Hajnoczi
QEMU currently truncates the mmap_offset field when sending VHOST_USER_ADD_MEM_REG and VHOST_USER_REM_MEM_REG messages. The struct layout looks like this: typedef struct VhostUserMemoryRegion { uint64_t guest_phys_addr; uint64_t memory_size; uint64_t userspace_addr; uint64_t mmap_offset; } VhostUserMemoryRegion; typedef struct VhostUserMemRegMsg { uint32_t padding; /* WARNING: there is a 32-bit hole here! */ VhostUserMemoryRegion region; } VhostUserMemRegMsg; The payload size is calculated as follows when sending the message in hw/virtio/vhost-user.c: msg->hdr.size = sizeof(msg->payload.mem_reg.padding) + sizeof(VhostUserMemoryRegion); This calculation produces an incorrect result of only 36 bytes. sizeof(VhostUserMemRegMsg) is actually 40 bytes. The consequence of this is that the final field, mmap_offset, is truncated. This breaks x86_64 TCG guests on s390 hosts. Other guest/host combinations may get lucky if either of the following holds: 1. The guest memory layout does not need mmap_offset != 0. 2. The host is little-endian and mmap_offset <= 0xffffffff so the truncation has no effect. Fix this by extending the existing 32-bit padding field to 64-bit. Now the padding reflects the actual compiler padding. This can be verified using pahole(1). Also document the layout properly in the vhost-user specification. The vhost-user spec did not document the exact layout. It would be impossible to implement the spec without looking at the QEMU source code. Existing vhost-user frontends and device backends continue to work after this fix has been applied. The only change in the wire protocol is that QEMU now sets hdr.size to 40 instead of 36. If a vhost-user implementation has a hardcoded size check for 36 bytes, then it will fail with new QEMUs. Both QEMU and DPDK/SPDK don't check the exact payload size, so they continue to work. Fixes: f1aeb14b0809e313c74244d838645ed25e85ea63 ("Transmit vhost-user memory regions individually") Cc: Raphael Norwitz <raphael.norwitz@nutanix.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20201109174355.1069147-1-stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Fixes: f1aeb14b0809 ("Transmit vhost-user memory regions individually") Reviewed-by: Cornelia Huck <cohuck@redhat.com> Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
2020-09-17docs/: fix some comment spelling errorszhaolichang
I found that there are many spelling errors in the comments of qemu, so I used the spellcheck tool to check the spelling errors and finally found some spelling errors in the docs folder. Signed-off-by: zhaolichang <zhaolichang@huawei.com> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Message-Id: <20200917075029.313-4-zhaolichang@huawei.com> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2020-07-03docs: vhost-user: add Virtio status protocol featureMaxime Coquelin
This patch specifies the VHOST_USER_SET_STATUS and VHOST_USER_GET_STATUS requests, which are sent by the master to update and query the Virtio status in the backend. Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com> Message-Id: <20200618134501.145747-1-maxime.coquelin@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-06-12Lift max memory slots limit imposed by vhost-userRaphael Norwitz
Historically, sending all memory regions to vhost-user backends in a single message imposed a limitation on the number of times memory could be hot-added to a VM with a vhost-user device. Now that backends which support the VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS send memory regions individually, we no longer need to impose this limitation on devices which support this feature. With this change, VMs with a vhost-user device which supports the VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS can support a configurable number of memory slots, up to the maximum allowed by the target platform. Existing backends which do not support VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS are unaffected. Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com> Signed-off-by: Peter Turschmid <peter.turschm@nutanix.com> Suggested-by: Mike Cui <cui@nutanix.com> Message-Id: <1588533678-23450-6-git-send-email-raphael.norwitz@nutanix.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>
2020-06-12Transmit vhost-user memory regions individuallyRaphael Norwitz
With this change, when the VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS protocol feature has been negotiated, Qemu no longer sends the backend all the memory regions in a single message. Rather, when the memory tables are set or updated, a series of VHOST_USER_ADD_MEM_REG and VHOST_USER_REM_MEM_REG messages are sent to transmit the regions to map and/or unmap instead of sending send all the regions in one fixed size VHOST_USER_SET_MEM_TABLE message. The vhost_user struct maintains a shadow state of the VM’s memory regions. When the memory tables are modified, the vhost_user_set_mem_table() function compares the new device memory state to the shadow state and only sends regions which need to be unmapped or mapped in. The regions which must be unmapped are sent first, followed by the new regions to be mapped in. After all the messages have been sent, the shadow state is set to the current virtual device state. Existing backends which do not support VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS are unaffected. Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com> Signed-off-by: Swapnil Ingle <swapnil.ingle@nutanix.com> Signed-off-by: Peter Turschmid <peter.turschm@nutanix.com> Suggested-by: Mike Cui <cui@nutanix.com> Message-Id: <1588533678-23450-5-git-send-email-raphael.norwitz@nutanix.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
2020-06-12Add VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTSRaphael Norwitz
This change introduces a new feature to the vhost-user protocol allowing a backend device to specify the maximum number of ram slots it supports. At this point, the value returned by the backend will be capped at the maximum number of ram slots which can be supported by vhost-user, which is currently set to 8 because of underlying protocol limitations. The returned value will be stored inside the VhostUserState struct so that on device reconnect we can verify that the ram slot limitation has not decreased since the last time the device connected. Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com> Signed-off-by: Peter Turschmid <peter.turschm@nutanix.com> Message-Id: <1588533678-23450-4-git-send-email-raphael.norwitz@nutanix.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>
2020-03-16misc: Replace zero-length arrays with flexible array member (manual)Philippe Mathieu-Daudé
Description copied from Linux kernel commit from Gustavo A. R. Silva (see [3]): --v-- description start --v-- The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member [1], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being unadvertenly introduced [2] to the Linux codebase from now on. --^-- description end --^-- Do the similar housekeeping in the QEMU codebase (which uses C99 since commit 7be41675f7cb). All these instances of code were found with the help of the following command (then manual analysis, without modifying structures only having a single flexible array member, such QEDTable in block/qed.h): git grep -F '[0];' [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=76497732932f [3] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?id=17642a2fbd2c1 Inspired-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-02-27docs: vhost-user: add in-band kick/call messagesJohannes Berg
For good reason, vhost-user is currently built asynchronously, that way better performance can be obtained. However, for certain use cases such as simulation, this is problematic. Consider an event-based simulation in which both the device and CPU have scheduled according to a simulation "calendar". Now, consider the CPU sending I/O to the device, over a vring in the vhost-user protocol. In this case, the CPU must wait for the vring interrupt to have been processed by the device, so that the device is able to put an entry onto the simulation calendar to obtain time to handle the interrupt. Note that this doesn't mean the I/O is actually done at this time, it just means that the handling of it is scheduled before the CPU can continue running. This cannot be done with the asynchronous eventfd based vring kick and call design. Extend the protocol slightly, so that a message can be used for kick and call instead, if VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS is negotiated. This in itself doesn't guarantee synchronisation, but both sides can also negotiate VHOST_USER_PROTOCOL_F_REPLY_ACK and thus get a reply to this message by setting the need_reply flag, and ensure synchronisation this way. To really use it in both directions, VHOST_USER_PROTOCOL_F_SLAVE_REQ is also needed. Since it is used for simulation purposes and too many messages on the socket can lock up the virtual machine, document that this should only be used together with the mentioned features. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Message-Id: <20200123081708.7817-6-johannes@sipsolutions.net> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-01-05vhost-user: add VHOST_USER_RESET_DEVICE to reset devicesRaphael Norwitz
Add a VHOST_USER_RESET_DEVICE message which will reset the vhost user backend. Disabling all rings, and resetting all internal state, ready for the backend to be reinitialized. A backend has to report it supports this features with the VHOST_USER_PROTOCOL_F_RESET_DEVICE protocol feature bit. If it does so, the new message is used instead of sending a RESET_OWNER which has had inconsistent implementations. Signed-off-by: David Vrabel <david.vrabel@nutanix.com> Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com> Message-Id: <1572385083-5254-2-git-send-email-raphael.norwitz@nutanix.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-01-05Implement backend program convention command for vhost-user-blkMicky Yun Chan
This patch is to add standard commands defined in docs/interop/vhost-user.rst For vhost-user-* program Signed-off-by: Micky Yun Chan (michiboo) <chanmickyyun@gmail.com> Message-Id: <20191209015331.5455-1-chanmickyyun@gmail.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2019-07-25docs: clarify multiqueue vs multiple virtqueuesStefan Hajnoczi
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>
2019-07-04docs: avoid vhost-user-net specifics in multiqueue sectionStefan Hajnoczi
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>
2019-05-29vhost-user: add vhost_user_gpu_set_socket()Marc-André Lureau
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>
2019-05-20docs: reST-ify vhost-user documentationMarc-André Lureau
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20190315180735.13096-1-marcandre.lureau@redhat.com> Reviewed-by: Jens Freimann <jfreimann@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>