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vhost_user: Add support for SHMEM_MAP/UNMAP backend requests #251

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vhost_user: Add support for SHMEM_MAP/UNMAP backend requests #251

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903cabf
backend_req::tests: Extract test setup to a function
mtjhrc Aug 28, 2024
e5d6184
vhost_user: Add support for SHMEM_MAP/UNMAP backend requests
aesteve-rh May 21, 2024
8ef77ef
Add tests for default impls of Frontend req handlers
mtjhrc Aug 28, 2024
993d885
Bump test coverage value for x86_64
mtjhrc Nov 26, 2025
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2 changes: 1 addition & 1 deletion coverage_config_x86_64.json
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
{
"coverage_score": 85.41,
"coverage_score": 86.22,
"exclude_path": "vhost/src/vhost_kern/",
"crate_features": "vhost/vhost-user-frontend,vhost/vhost-user-backend,vhost-user-backend/postcopy"
}
2 changes: 2 additions & 0 deletions vhost/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,8 @@
## [Unreleased]

### Added
- [[#251]](https://github.com/rust-vmm/vhost/pull/251) Add `SHMEM_MAP` and `SHMEM_UNMAP` support

### Changed
### Deprecated
### Fixed
Expand Down
73 changes: 66 additions & 7 deletions vhost/src/vhost_user/backend_req.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -174,6 +174,16 @@ impl VhostUserFrontendReqHandler for Backend {
Some(&[fd.as_raw_fd()]),
)
}

/// Forward vhost-user memory map file request to the frontend.
fn shmem_map(&self, req: &VhostUserMMap, fd: &dyn AsRawFd) -> HandlerResult<u64> {
self.send_message(BackendReq::SHMEM_MAP, req, Some(&[fd.as_raw_fd()]))
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@stefano-garzarella stefano-garzarella Dec 2, 2025

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In shared_object_*() functions above we check if the related feature is negotiated, should we do something similar also here?

}

/// Forward vhost-user memory unmap file request to the frontend.
fn shmem_unmap(&self, req: &VhostUserMMap) -> HandlerResult<u64> {
self.send_message(BackendReq::SHMEM_UNMAP, req, None)
}
}

#[cfg(test)]
Expand All @@ -182,10 +192,16 @@ mod tests {

use super::*;

fn frontend_backend_pair() -> (Endpoint<VhostUserMsgHeader<BackendReq>>, Backend) {
let (p1, p2) = UnixStream::pair().unwrap();
let backend = Backend::from_stream(p1);
let frontend = Endpoint::<VhostUserMsgHeader<BackendReq>>::from_stream(p2);
(frontend, backend)
}

#[test]
fn test_backend_req_set_failed() {
let (p1, _p2) = UnixStream::pair().unwrap();
let backend = Backend::from_stream(p1);
let (_, backend) = frontend_backend_pair();

assert!(backend.node().error.is_none());
backend.set_failed(libc::EAGAIN);
Expand All @@ -194,8 +210,7 @@ mod tests {

#[test]
fn test_backend_req_send_failure() {
let (p1, _) = UnixStream::pair().unwrap();
let backend = Backend::from_stream(p1);
let (_, backend) = frontend_backend_pair();

backend.set_failed(libc::ECONNRESET);
backend
Expand All @@ -209,9 +224,7 @@ mod tests {

#[test]
fn test_backend_req_recv_negative() {
let (p1, p2) = UnixStream::pair().unwrap();
let backend = Backend::from_stream(p1);
let mut frontend = Endpoint::<VhostUserMsgHeader<BackendReq>>::from_stream(p2);
let (mut frontend, backend) = frontend_backend_pair();

let len = mem::size_of::<VhostUserSharedMsg>();
let mut hdr = VhostUserMsgHeader::new(
Expand Down Expand Up @@ -257,4 +270,50 @@ mod tests {
.shared_object_add(&VhostUserSharedMsg::default())
.unwrap();
}

#[test]
fn test_shmem_map() {
let (mut frontend, backend) = frontend_backend_pair();

let (_, some_fd_to_send) = UnixStream::pair().unwrap();
let map_request = VhostUserMMap {
shmid: 0,
padding: Default::default(),
fd_offset: 0,
shm_offset: 1028,
len: 4096,
flags: VhostUserMMapFlags::WRITABLE.bits(),
};

backend.shmem_map(&map_request, &some_fd_to_send).unwrap();

let (hdr, request, fd) = frontend.recv_body::<VhostUserMMap>().unwrap();
assert_eq!(hdr.get_code().unwrap(), BackendReq::SHMEM_MAP);
assert!(fd.is_some());
assert_eq!({ request.shm_offset }, { map_request.shm_offset });
assert_eq!({ request.len }, { map_request.len },);
assert_eq!({ request.flags }, { map_request.flags });
}

#[test]
fn test_shmem_unmap() {
let (mut frontend, backend) = frontend_backend_pair();

let unmap_request = VhostUserMMap {
shmid: 0,
padding: Default::default(),
fd_offset: 0,
shm_offset: 1028,
len: 4096,
flags: 0,
};

backend.shmem_unmap(&unmap_request).unwrap();

let (hdr, request, fd) = frontend.recv_body::<VhostUserMMap>().unwrap();
assert_eq!(hdr.get_code().unwrap(), BackendReq::SHMEM_UNMAP);
assert!(fd.is_none());
assert_eq!({ request.shm_offset }, { unmap_request.shm_offset });
assert_eq!({ request.len }, { unmap_request.len });
}
}
177 changes: 176 additions & 1 deletion vhost/src/vhost_user/frontend_req_handler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,16 @@ pub trait VhostUserFrontendReqHandler {
Err(std::io::Error::from_raw_os_error(libc::ENOSYS))
}

/// Handle shared memory region mapping requests.
fn shmem_map(&self, _req: &VhostUserMMap, _fd: &dyn AsRawFd) -> HandlerResult<u64> {
Err(std::io::Error::from_raw_os_error(libc::ENOSYS))
}

/// Handle shared memory region unmapping requests.
fn shmem_unmap(&self, _req: &VhostUserMMap) -> HandlerResult<u64> {
Err(std::io::Error::from_raw_os_error(libc::ENOSYS))
}

// fn handle_iotlb_msg(&mut self, iotlb: VhostUserIotlb);
// fn handle_vring_host_notifier(&mut self, area: VhostUserVringArea, fd: &dyn AsRawFd);
}
Expand Down Expand Up @@ -84,6 +94,16 @@ pub trait VhostUserFrontendReqHandlerMut {
Err(std::io::Error::from_raw_os_error(libc::ENOSYS))
}

/// Handle shared memory region mapping requests.
fn shmem_map(&mut self, _req: &VhostUserMMap, _fd: &dyn AsRawFd) -> HandlerResult<u64> {
Err(std::io::Error::from_raw_os_error(libc::ENOSYS))
}

/// Handle shared memory region unmapping requests.
fn shmem_unmap(&mut self, _req: &VhostUserMMap) -> HandlerResult<u64> {
Err(std::io::Error::from_raw_os_error(libc::ENOSYS))
}

// fn handle_iotlb_msg(&mut self, iotlb: VhostUserIotlb);
// fn handle_vring_host_notifier(&mut self, area: VhostUserVringArea, fd: RawFd);
}
Expand Down Expand Up @@ -111,6 +131,14 @@ impl<S: VhostUserFrontendReqHandlerMut> VhostUserFrontendReqHandler for Mutex<S>
) -> HandlerResult<u64> {
self.lock().unwrap().shared_object_lookup(uuid, fd)
}

fn shmem_map(&self, req: &VhostUserMMap, fd: &dyn AsRawFd) -> HandlerResult<u64> {
self.lock().unwrap().shmem_map(req, fd)
}

fn shmem_unmap(&self, req: &VhostUserMMap) -> HandlerResult<u64> {
self.lock().unwrap().shmem_unmap(req)
}
}

/// Server to handle service requests from backends from the backend communication channel.
Expand Down Expand Up @@ -241,6 +269,18 @@ impl<S: VhostUserFrontendReqHandler> FrontendReqHandler<S> {
.shared_object_lookup(&msg, &files.unwrap()[0])
.map_err(Error::ReqHandlerError)
}
Ok(BackendReq::SHMEM_MAP) => {
let msg = self.extract_msg_body::<VhostUserMMap>(&hdr, size, &buf)?;
self.backend
.shmem_map(&msg, &files.unwrap()[0])
.map_err(Error::ReqHandlerError)
}
Ok(BackendReq::SHMEM_UNMAP) => {
let msg = self.extract_msg_body::<VhostUserMMap>(&hdr, size, &buf)?;
self.backend
.shmem_unmap(&msg)
.map_err(Error::ReqHandlerError)
}
_ => Err(Error::InvalidMessage),
};

Expand Down Expand Up @@ -278,7 +318,7 @@ impl<S: VhostUserFrontendReqHandler> FrontendReqHandler<S> {
files: &Option<Vec<File>>,
) -> Result<()> {
match hdr.get_code() {
Ok(BackendReq::SHARED_OBJECT_LOOKUP) => {
Ok(BackendReq::SHARED_OBJECT_LOOKUP | BackendReq::SHMEM_MAP) => {
// Expect a single file is passed.
match files {
Some(files) if files.len() == 1 => Ok(()),
Expand Down Expand Up @@ -356,6 +396,7 @@ mod tests {
use super::*;

use std::collections::HashSet;
use std::io::ErrorKind;

use uuid::Uuid;

Expand All @@ -366,12 +407,14 @@ mod tests {

struct MockFrontendReqHandler {
shared_objects: HashSet<Uuid>,
shmem_mappings: HashSet<(u64, u64)>,
}

impl MockFrontendReqHandler {
fn new() -> Self {
Self {
shared_objects: HashSet::new(),
shmem_mappings: HashSet::new(),
}
}
}
Expand All @@ -395,6 +438,88 @@ mod tests {
}
Ok(1)
}

fn shmem_map(&mut self, req: &VhostUserMMap, _fd: &dyn AsRawFd) -> HandlerResult<u64> {
assert_eq!({ req.shmid }, 0);
if self.shmem_mappings.insert((req.shm_offset, req.len)) {
return Ok(0);
};
Ok(1)
}

fn shmem_unmap(&mut self, req: &VhostUserMMap) -> HandlerResult<u64> {
assert_eq!({ req.shmid }, 0);
if self.shmem_mappings.remove(&(req.shm_offset, req.len)) {
return Ok(0);
}
Ok(1)
}
}

#[test]
fn test_default_frontend_impl() {
struct Frontend;
impl VhostUserFrontendReqHandler for Frontend {}

let f = Frontend;
assert_eq!(
f.shared_object_add(&Default::default()).unwrap_err().kind(),
ErrorKind::Unsupported
);
assert_eq!(
f.shared_object_remove(&Default::default())
.unwrap_err()
.kind(),
ErrorKind::Unsupported
);
assert_eq!(
f.shared_object_lookup(&Default::default(), &0)
.unwrap_err()
.kind(),
ErrorKind::Unsupported
);

assert_eq!(
f.shmem_map(&Default::default(), &0).unwrap_err().kind(),
ErrorKind::Unsupported
);
assert_eq!(
f.shmem_unmap(&Default::default()).unwrap_err().kind(),
ErrorKind::Unsupported
);
}

#[test]
fn test_default_frontend_impl_mut() {
struct FrontendMut;
impl VhostUserFrontendReqHandlerMut for FrontendMut {}

let mut f = FrontendMut;
assert_eq!(
f.shared_object_add(&Default::default()).unwrap_err().kind(),
ErrorKind::Unsupported
);
assert_eq!(
f.shared_object_remove(&Default::default())
.unwrap_err()
.kind(),
ErrorKind::Unsupported
);
assert_eq!(
f.shared_object_lookup(&Default::default(), &0)
.unwrap_err()
.kind(),
ErrorKind::Unsupported
);

assert_eq!(
f.shmem_map(&Default::default(), &0).unwrap_err().kind(),
ErrorKind::Unsupported
);
assert_eq!(
f.shmem_unmap(&Default::default()).unwrap_err().kind(),
ErrorKind::Unsupported
);
}

#[test]
Expand Down Expand Up @@ -436,6 +561,13 @@ mod tests {
assert_eq!(handler.handle_request().unwrap(), 1);
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 1);

// Testing shmem map/unmap messages.
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 1);
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 0);
});

backend.set_shared_object_flag(true);
Expand All @@ -456,6 +588,24 @@ mod tests {
.is_ok());
assert!(backend.shared_object_remove(&shobj_msg).is_ok());
assert!(backend.shared_object_remove(&shobj_msg).is_ok());

let (_, some_fd_to_map) = UnixStream::pair().unwrap();
let map_request1 = VhostUserMMap {
shm_offset: 0,
len: 4096,
..Default::default()
};
let map_request2 = VhostUserMMap {
shm_offset: 4096,
len: 8192,
..Default::default()
};
backend.shmem_map(&map_request1, &some_fd_to_map).unwrap();
backend.shmem_unmap(&map_request2).unwrap();
backend.shmem_map(&map_request2, &some_fd_to_map).unwrap();
backend.shmem_unmap(&map_request2).unwrap();
backend.shmem_unmap(&map_request1).unwrap();

// Ensure that the handler thread did not panic.
assert!(frontend_handler.join().is_ok());
}
Expand Down Expand Up @@ -485,6 +635,13 @@ mod tests {
assert_eq!(handler.handle_request().unwrap(), 1);
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 1);

// Testing shmem map/unmap messages.
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 1);
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 0);
assert_eq!(handler.handle_request().unwrap(), 0);
});

backend.set_reply_ack_flag(true);
Expand All @@ -506,6 +663,24 @@ mod tests {
.is_err());
assert!(backend.shared_object_remove(&shobj_msg).is_ok());
assert!(backend.shared_object_remove(&shobj_msg).is_err());

let (_, some_fd_to_map) = UnixStream::pair().unwrap();
let map_request1 = VhostUserMMap {
shm_offset: 0,
len: 4096,
..Default::default()
};
let map_request2 = VhostUserMMap {
shm_offset: 4096,
len: 8192,
..Default::default()
};
backend.shmem_map(&map_request1, &some_fd_to_map).unwrap();
backend.shmem_unmap(&map_request2).unwrap_err();
backend.shmem_map(&map_request2, &some_fd_to_map).unwrap();
backend.shmem_unmap(&map_request2).unwrap();
backend.shmem_unmap(&map_request1).unwrap();

// Ensure that the handler thread did not panic.
assert!(frontend_handler.join().is_ok());
}
Expand Down
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