/// Client for a vhost-user device. The API is a thin abstraction over the vhost-user protocol.
pub struct BackendClient {
connection: Connection<FrontendReq>,
// Cached virtio features from the backend.
virtio_features: u64,
// Cached acked virtio features from the driver.
acked_virtio_features: u64,
// Cached vhost-user protocol features.
acked_protocol_features: u64,
}
impl BackendClient {
/// Create a new instance.
pub fn new(connection: Connection<FrontendReq>) -> Self {
BackendClient {
connection,
virtio_features: 0,
acked_virtio_features: 0,
acked_protocol_features: 0,
}
}
/// Get a bitmask of supported virtio/vhost features.
pub fn get_features(&mut self) -> Result<u64> {
let hdr = self.send_request_header(FrontendReq::GET_FEATURES, None)?;
let val = self.recv_reply::<VhostUserU64>(&hdr)?;
self.virtio_features = val.value;
Ok(self.virtio_features)
}
/// Inform the vhost subsystem which features to enable.
/// This should be a subset of supported features from get_features().
pub fn set_features(&mut self, features: u64) -> Result<()> {
let val = VhostUserU64::new(features);
let hdr = self.send_request_with_body(FrontendReq::SET_FEATURES, &val, None)?;
self.acked_virtio_features = features & self.virtio_features;
self.wait_for_ack(&hdr)
}
/// Set the current process as the owner of the vhost backend.
/// This must be run before any other vhost commands.
pub fn set_owner(&self) -> Result<()> {
let hdr = self.send_request_header(FrontendReq::SET_OWNER, None)?;
self.wait_for_ack(&hdr)
}
/// Used to be sent to request disabling all rings
/// This is no longer used.
pub fn reset_owner(&self) -> Result<()> {
let hdr = self.send_request_header(FrontendReq::RESET_OWNER, None)?;
self.wait_for_ack(&hdr)
}
/// Set the memory map regions on the backend so it can translate the vring
/// addresses. In the ancillary data there is an array of file descriptors
pub fn set_mem_table(&self, regions: &[VhostUserMemoryRegionInfo]) -> Result<()> {
if regions.is_empty() || regions.len() > MAX_ATTACHED_FD_ENTRIES {
return Err(VhostUserError::InvalidParam(
"set_mem_table: regions empty or exceed max allowed regions per req.",
));
}
let mut ctx = VhostUserMemoryContext::new();
for region in regions.iter() {
if region.memory_size == 0 || region.mmap_handle == INVALID_DESCRIPTOR {
return Err(VhostUserError::InvalidParam(
"set_mem_table: invalid memory region",
));
}
let reg = VhostUserMemoryRegion {
guest_phys_addr: region.guest_phys_addr,
memory_size: region.memory_size,
user_addr: region.userspace_addr,
mmap_offset: region.mmap_offset,
};
ctx.append(®, region.mmap_handle);
}
let body = VhostUserMemory::new(ctx.regions.len() as u32);
let hdr = self.send_request_with_payload(
FrontendReq::SET_MEM_TABLE,
&body,
ctx.regions.as_bytes(),
Some(ctx.fds.as_slice()),
)?;
self.wait_for_ack(&hdr)
}
/// Set base address for page modification logging.
pub fn set_log_base(&self, base: u64, fd: Option<RawDescriptor>) -> Result<()> {
let val = VhostUserU64::new(base);
let should_have_fd =
self.acked_protocol_features & VhostUserProtocolFeatures::LOG_SHMFD.bits() != 0;
if should_have_fd != fd.is_some() {
return Err(VhostUserError::InvalidParam("set_log_base: FD is missing"));
}
let _ = self.send_request_with_body(
FrontendReq::SET_LOG_BASE,
&val,
fd.as_ref().map(std::slice::from_ref),
)?;
Ok(())
}
/// Specify an event file descriptor to signal on log write.
pub fn set_log_fd(&self, fd: RawDescriptor) -> Result<()> {
let fds = [fd];
let hdr = self.send_request_header(FrontendReq::SET_LOG_FD, Some(&fds))?;
self.wait_for_ack(&hdr)
}
/// Set the number of descriptors in the vring.
pub fn set_vring_num(&self, queue_index: usize, num: u16) -> Result<()> {
let val = VhostUserVringState::new(queue_index as u32, num.into());
let hdr = self.send_request_with_body(FrontendReq::SET_VRING_NUM, &val, None)?;
self.wait_for_ack(&hdr)
}
/// Set the addresses for a given vring.
pub fn set_vring_addr(&self, queue_index: usize, config_data: &VringConfigData) -> Result<()> {
if config_data.flags & !(VhostUserVringAddrFlags::all().bits()) != 0 {
return Err(VhostUserError::InvalidParam(
"set_vring_addr: unsupported vring flags",
));
}
let val = VhostUserVringAddr::from_config_data(queue_index as u32, config_data);
let hdr = self.send_request_with_body(FrontendReq::SET_VRING_ADDR, &val, None)?;
self.wait_for_ack(&hdr)
}
/// Set the first index to look for available descriptors.
// TODO: b/331466964 - Arguments and message format are wrong for packed queues.
pub fn set_vring_base(&self, queue_index: usize, base: u16) -> Result<()> {
let val = VhostUserVringState::new(queue_index as u32, base.into());
let hdr = self.send_request_with_body(FrontendReq::SET_VRING_BASE, &val, None)?;
self.wait_for_ack(&hdr)
}
/// Get the available vring base offset.
// TODO: b/331466964 - Return type is wrong for packed queues.
pub fn get_vring_base(&self, queue_index: usize) -> Result<u32> {
let req = VhostUserVringState::new(queue_index as u32, 0);
let hdr = self.send_request_with_body(FrontendReq::GET_VRING_BASE, &req, None)?;
let reply = self.recv_reply::<VhostUserVringState>(&hdr)?;
Ok(reply.num)
}
/// Set the event to trigger when buffers have been used by the host.
///
/// Bits (0-7) of the payload contain the vring index. Bit 8 is the invalid FD flag. This flag
/// is set when there is no file descriptor in the ancillary data. This signals that polling
/// will be used instead of waiting for the call.
pub fn set_vring_call(&self, queue_index: usize, event: &Event) -> Result<()> {
let hdr = self.send_fd_for_vring(
FrontendReq::SET_VRING_CALL,
queue_index,
event.as_raw_descriptor(),
)?;
self.wait_for_ack(&hdr)
}
/// Set the event that will be signaled by the guest when buffers are available for the host to
/// process.
///
/// Bits (0-7) of the payload contain the vring index. Bit 8 is the invalid FD flag. This flag
/// is set when there is no file descriptor in the ancillary data. This signals that polling
/// should be used instead of waiting for a kick.
pub fn set_vring_kick(&self, queue_index: usize, event: &Event) -> Result<()> {
let hdr = self.send_fd_for_vring(
FrontendReq::SET_VRING_KICK,
queue_index,
event.as_raw_descriptor(),
)?;
self.wait_for_ack(&hdr)
}
/// Set the event that will be signaled by the guest when error happens.
///
/// Bits (0-7) of the payload contain the vring index. Bit 8 is the invalid FD flag. This flag
/// is set when there is no file descriptor in the ancillary data.
pub fn set_vring_err(&self, queue_index: usize, event: &Event) -> Result<()> {
let hdr = self.send_fd_for_vring(
FrontendReq::SET_VRING_ERR,
queue_index,
event.as_raw_descriptor(),
)?;
self.wait_for_ack(&hdr)
}
/// Front-end and back-end negotiate a channel over which to transfer the back-end’s internal
/// state during migration.
///
/// Requires VHOST_USER_PROTOCOL_F_DEVICE_STATE to be negotiated.
pub fn set_device_state_fd(
&self,
transfer_direction: VhostUserTransferDirection,
migration_phase: VhostUserMigrationPhase,
fd: &impl AsRawDescriptor,
) -> Result<Option<File>> {
if self.acked_protocol_features & VhostUserProtocolFeatures::DEVICE_STATE.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
// Send request.
let req = DeviceStateTransferParameters {
transfer_direction: match transfer_direction {
VhostUserTransferDirection::Save => 0,
VhostUserTransferDirection::Load => 1,
},
migration_phase: match migration_phase {
VhostUserMigrationPhase::Stopped => 0,
},
};
let hdr = self.send_request_with_body(
FrontendReq::SET_DEVICE_STATE_FD,
&req,
Some(&[fd.as_raw_descriptor()]),
)?;
// Receive reply.
let (reply, files) = self.recv_reply_with_files::<VhostUserU64>(&hdr)?;
let has_err = reply.value & 0xff != 0;
let invalid_fd = reply.value & 0x100 != 0;
if has_err {
return Err(VhostUserError::BackendInternalError);
}
match (invalid_fd, files.len()) {
(true, 0) => Ok(None),
(false, 1) => Ok(files.into_iter().next()),
_ => Err(VhostUserError::IncorrectFds),
}
}
/// After transferring the back-end’s internal state during migration, check whether the
/// back-end was able to successfully fully process the state.
pub fn check_device_state(&self) -> Result<()> {
if self.acked_protocol_features & VhostUserProtocolFeatures::DEVICE_STATE.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
let hdr = self.send_request_header(FrontendReq::CHECK_DEVICE_STATE, None)?;
let reply = self.recv_reply::<VhostUserU64>(&hdr)?;
if reply.value != 0 {
return Err(VhostUserError::BackendInternalError);
}
Ok(())
}
/// Get the protocol feature bitmask from the underlying vhost implementation.
pub fn get_protocol_features(&self) -> Result<VhostUserProtocolFeatures> {
if self.virtio_features & 1 << VHOST_USER_F_PROTOCOL_FEATURES == 0 {
return Err(VhostUserError::InvalidOperation);
}
let hdr = self.send_request_header(FrontendReq::GET_PROTOCOL_FEATURES, None)?;
let val = self.recv_reply::<VhostUserU64>(&hdr)?;
Ok(VhostUserProtocolFeatures::from_bits_truncate(val.value))
}
/// Enable protocol features in the underlying vhost implementation.
pub fn set_protocol_features(&mut self, features: VhostUserProtocolFeatures) -> Result<()> {
if self.virtio_features & 1 << VHOST_USER_F_PROTOCOL_FEATURES == 0 {
return Err(VhostUserError::InvalidOperation);
}
if features.contains(VhostUserProtocolFeatures::SHARED_MEMORY_REGIONS)
&& !features.contains(VhostUserProtocolFeatures::BACKEND_REQ)
{
return Err(VhostUserError::FeatureMismatch);
}
let val = VhostUserU64::new(features.bits());
let hdr = self.send_request_with_body(FrontendReq::SET_PROTOCOL_FEATURES, &val, None)?;
// Don't wait for ACK here because the protocol feature negotiation process hasn't been
// completed yet.
self.acked_protocol_features = features.bits();
self.wait_for_ack(&hdr)
}
/// Query how many queues the backend supports.
pub fn get_queue_num(&self) -> Result<u64> {
if !self.is_feature_mq_available() {
return Err(VhostUserError::InvalidOperation);
}
let hdr = self.send_request_header(FrontendReq::GET_QUEUE_NUM, None)?;
let val = self.recv_reply::<VhostUserU64>(&hdr)?;
if val.value > VHOST_USER_MAX_VRINGS {
return Err(VhostUserError::InvalidMessage);
}
Ok(val.value)
}
/// Signal backend to enable or disable corresponding vring.
///
/// Backend must not pass data to/from the ring until ring is enabled by
/// VHOST_USER_SET_VRING_ENABLE with parameter 1, or after it has been
/// disabled by VHOST_USER_SET_VRING_ENABLE with parameter 0.
pub fn set_vring_enable(&self, queue_index: usize, enable: bool) -> Result<()> {
// set_vring_enable() is supported only when PROTOCOL_FEATURES has been enabled.
if self.acked_virtio_features & 1 << VHOST_USER_F_PROTOCOL_FEATURES == 0 {
return Err(VhostUserError::InvalidOperation);
}
let val = VhostUserVringState::new(queue_index as u32, enable.into());
let hdr = self.send_request_with_body(FrontendReq::SET_VRING_ENABLE, &val, None)?;
self.wait_for_ack(&hdr)
}
/// Fetch the contents of the virtio device configuration space.
pub fn get_config(
&self,
offset: u32,
size: u32,
flags: VhostUserConfigFlags,
buf: &[u8],
) -> Result<(VhostUserConfig, VhostUserConfigPayload)> {
let body = VhostUserConfig::new(offset, size, flags);
if !body.is_valid() {
return Err(VhostUserError::InvalidParam(
"get_config: VhostUserConfig is invalid",
));
}
// depends on VhostUserProtocolFeatures::CONFIG
if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIG.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
// vhost-user spec states that:
// "Request payload: virtio device config space"
// "Reply payload: virtio device config space"
let hdr = self.send_request_with_payload(FrontendReq::GET_CONFIG, &body, buf, None)?;
let (body_reply, buf_reply, rfds) =
self.recv_reply_with_payload::<VhostUserConfig>(&hdr)?;
if !rfds.is_empty() {
return Err(VhostUserError::InvalidMessage);
} else if body_reply.size == 0 {
return Err(VhostUserError::BackendInternalError);
} else if body_reply.size != body.size
|| body_reply.size as usize != buf.len()
|| body_reply.offset != body.offset
{
return Err(VhostUserError::InvalidMessage);
}
Ok((body_reply, buf_reply))
}
/// Change the virtio device configuration space. It also can be used for live migration on the
/// destination host to set readonly configuration space fields.
pub fn set_config(&self, offset: u32, flags: VhostUserConfigFlags, buf: &[u8]) -> Result<()> {
let body = VhostUserConfig::new(
offset,
buf.len()
.try_into()
.map_err(VhostUserError::InvalidCastToInt)?,
flags,
);
if !body.is_valid() {
return Err(VhostUserError::InvalidParam(
"set_config: VhostUserConfig is invalid",
));
}
// depends on VhostUserProtocolFeatures::CONFIG
if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIG.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
let hdr = self.send_request_with_payload(FrontendReq::SET_CONFIG, &body, buf, None)?;
self.wait_for_ack(&hdr)
}
/// Setup backend communication channel.
pub fn set_backend_req_fd(&self, fd: &dyn AsRawDescriptor) -> Result<()> {
if self.acked_protocol_features & VhostUserProtocolFeatures::BACKEND_REQ.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
let fds = [fd.as_raw_descriptor()];
let hdr = self.send_request_header(FrontendReq::SET_BACKEND_REQ_FD, Some(&fds))?;
self.wait_for_ack(&hdr)
}
/// Retrieve shared buffer for inflight I/O tracking.
pub fn get_inflight_fd(
&self,
inflight: &VhostUserInflight,
) -> Result<(VhostUserInflight, File)> {
if self.acked_protocol_features & VhostUserProtocolFeatures::INFLIGHT_SHMFD.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
let hdr = self.send_request_with_body(FrontendReq::GET_INFLIGHT_FD, inflight, None)?;
let (inflight, files) = self.recv_reply_with_files::<VhostUserInflight>(&hdr)?;
match into_single_file(files) {
Some(file) => Ok((inflight, file)),
None => Err(VhostUserError::IncorrectFds),
}
}
/// Set shared buffer for inflight I/O tracking.
pub fn set_inflight_fd(&self, inflight: &VhostUserInflight, fd: RawDescriptor) -> Result<()> {
if self.acked_protocol_features & VhostUserProtocolFeatures::INFLIGHT_SHMFD.bits() == 0 {
return Err(VhostUserError::InvalidOperation);
}
if inflight.mmap_size == 0
|| inflight.num_queues == 0
|| inflight.queue_size == 0
|| fd == INVALID_DESCRIPTOR
{
return Err(VhostUserError::InvalidParam(
"set_inflight_fd: invalid fd or params",
));
}
let hdr =
self.send_request_with_body(FrontendReq::SET_INFLIGHT_FD, inflight, Some(&[fd]))?;
self.wait_for_ack(&hdr)
}
/// Query the maximum amount of memory slots supported by the backend.
pub fn get_max_mem_slots(&self) -> Result<u64> {
if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits() == 0
{
return Err(VhostUserError::InvalidOperation);
}
let hdr = self.send_request_header(FrontendReq::GET_MAX_MEM_SLOTS, None)?;
let val = self.recv_reply::<VhostUserU64>(&hdr)?;
Ok(val.value)
}
/// Add a new guest memory mapping for vhost to use.
pub fn add_mem_region(&self, region: &VhostUserMemoryRegionInfo) -> Result<()> {
if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits() == 0
{
return Err(VhostUserError::InvalidOperation);
}
if region.memory_size == 0 || region.mmap_handle == INVALID_DESCRIPTOR {
return Err(VhostUserError::InvalidParam(
"add_mem_region: region empty or mmap handle invalid",
));
}
let body = VhostUserSingleMemoryRegion::new(
region.guest_phys_addr,
region.memory_size,
region.userspace_addr,
region.mmap_offset,
);
let fds = [region.mmap_handle];
let hdr = self.send_request_with_body(FrontendReq::ADD_MEM_REG, &body, Some(&fds))?;
self.wait_for_ack(&hdr)
}
/// Remove a guest memory mapping from vhost.
pub fn remove_mem_region(&self, region: &VhostUserMemoryRegionInfo) -> Result<()> {
if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits() == 0
{
return Err(VhostUserError::InvalidOperation);
}
if region.memory_size == 0 {
return Err(VhostUserError::InvalidParam(
"remove_mem_region: cannot remove zero sized region",
));
}
let body = VhostUserSingleMemoryRegion::new(
region.guest_phys_addr,
region.memory_size,
region.userspace_addr,
region.mmap_offset,
);
let hdr = self.send_request_with_body(FrontendReq::REM_MEM_REG, &body, None)?;
self.wait_for_ack(&hdr)
}
/// Gets the shared memory regions used by the device.
pub fn get_shared_memory_regions(&self) -> Result<Vec<VhostSharedMemoryRegion>> {
let hdr = self.send_request_header(FrontendReq::GET_SHARED_MEMORY_REGIONS, None)?;
let (body_reply, buf_reply, rfds) = self.recv_reply_with_payload::<VhostUserU64>(&hdr)?;
let struct_size = mem::size_of::<VhostSharedMemoryRegion>();
if !rfds.is_empty() || buf_reply.len() != body_reply.value as usize * struct_size {
return Err(VhostUserError::InvalidMessage);
}
let mut regions = Vec::new();
let mut offset = 0;
for _ in 0..body_reply.value {
regions.push(
// Can't fail because the input is the correct size.
VhostSharedMemoryRegion::read_from(&buf_reply[offset..(offset + struct_size)])
.unwrap(),
);
offset += struct_size;
}
Ok(regions)
}
fn send_request_header(
&self,
code: FrontendReq,
fds: Option<&[RawDescriptor]>,
) -> VhostUserResult<VhostUserMsgHeader<FrontendReq>> {
let hdr = self.new_request_header(code, 0);
self.connection.send_header_only_message(&hdr, fds)?;
Ok(hdr)
}
fn send_request_with_body<T: Sized + AsBytes>(
&self,
code: FrontendReq,
msg: &T,
fds: Option<&[RawDescriptor]>,
) -> VhostUserResult<VhostUserMsgHeader<FrontendReq>> {
let hdr = self.new_request_header(code, mem::size_of::<T>() as u32);
self.connection.send_message(&hdr, msg, fds)?;
Ok(hdr)
}
fn send_request_with_payload<T: Sized + AsBytes>(
&self,
code: FrontendReq,
msg: &T,
payload: &[u8],
fds: Option<&[RawDescriptor]>,
) -> VhostUserResult<VhostUserMsgHeader<FrontendReq>> {
if let Some(fd_arr) = fds {
if fd_arr.len() > MAX_ATTACHED_FD_ENTRIES {
return Err(VhostUserError::InvalidParam(
"send_request_with_payload: too many FDs supplied with message",
));
}
}
let len = mem::size_of::<T>()
.checked_add(payload.len())
.ok_or(VhostUserError::OversizedMsg)?;
let hdr = self.new_request_header(
code,
len.try_into().map_err(VhostUserError::InvalidCastToInt)?,
);
self.connection
.send_message_with_payload(&hdr, msg, payload, fds)?;
Ok(hdr)
}
fn send_fd_for_vring(
&self,
code: FrontendReq,
queue_index: usize,
fd: RawDescriptor,
) -> VhostUserResult<VhostUserMsgHeader<FrontendReq>> {
// Bits (0-7) of the payload contain the vring index. Bit 8 is the invalid FD flag.
// This flag is set when there is no file descriptor in the ancillary data. This signals
// that polling will be used instead of waiting for the call.
let msg = VhostUserU64::new(queue_index as u64);
let hdr = self.new_request_header(code, mem::size_of::<VhostUserU64>() as u32);
self.connection.send_message(&hdr, &msg, Some(&[fd]))?;
Ok(hdr)
}
fn recv_reply<T: Sized + FromBytes + AsBytes + Default + VhostUserMsgValidator>(
&self,
hdr: &VhostUserMsgHeader<FrontendReq>,
) -> VhostUserResult<T> {
if hdr.is_reply() {
return Err(VhostUserError::InvalidParam(
"recv_reply: header is not a reply",
));
}
let (reply, body, rfds) = self.connection.recv_message::<T>()?;
if !reply.is_reply_for(hdr) || !rfds.is_empty() || !body.is_valid() {
return Err(VhostUserError::InvalidMessage);
}
Ok(body)
}
fn recv_reply_with_files<T: Sized + AsBytes + FromBytes + Default + VhostUserMsgValidator>(
&self,
hdr: &VhostUserMsgHeader<FrontendReq>,
) -> VhostUserResult<(T, Vec<File>)> {
if hdr.is_reply() {
return Err(VhostUserError::InvalidParam(
"with_files: expected a reply, but the header is not marked as a reply",
));
}
let (reply, body, files) = self.connection.recv_message::<T>()?;
if !reply.is_reply_for(hdr) || !body.is_valid() {
return Err(VhostUserError::InvalidMessage);
}
Ok((body, files))
}
fn recv_reply_with_payload<T: Sized + AsBytes + FromBytes + Default + VhostUserMsgValidator>(
&self,
hdr: &VhostUserMsgHeader<FrontendReq>,
) -> VhostUserResult<(T, Vec<u8>, Vec<File>)> {
if hdr.is_reply() {
return Err(VhostUserError::InvalidParam(
"with_payload: expected a reply, but the header is not marked as a reply",
));
}
let (reply, body, buf, files) = self.connection.recv_message_with_payload::<T>()?;
if !reply.is_reply_for(hdr) || !files.is_empty() || !body.is_valid() {
return Err(VhostUserError::InvalidMessage);
}
Ok((body, buf, files))
}
fn wait_for_ack(&self, hdr: &VhostUserMsgHeader<FrontendReq>) -> VhostUserResult<()> {
if self.acked_protocol_features & VhostUserProtocolFeatures::REPLY_ACK.bits() == 0
|| !hdr.is_need_reply()
{
return Ok(());
}
let (reply, body, rfds) = self.connection.recv_message::<VhostUserU64>()?;
if !reply.is_reply_for(hdr) || !rfds.is_empty() || !body.is_valid() {
return Err(VhostUserError::InvalidMessage);
}
if body.value != 0 {
return Err(VhostUserError::BackendInternalError);
}
Ok(())
}
fn is_feature_mq_available(&self) -> bool {
self.acked_protocol_features & VhostUserProtocolFeatures::MQ.bits() != 0
}
#[inline]
fn new_request_header(
&self,
request: FrontendReq,
size: u32,
) -> VhostUserMsgHeader<FrontendReq> {
VhostUserMsgHeader::new(request, 0x1, size)
}
}
博客围绕Red Hat Enterprise Linux环境展开，主要探讨如何检查进程中被阻塞的信号。介绍了SigPnd、SigBlk、SigIgn、SigCgt等信号相关信息，并以SigBlk为例，说明了如何读取其位掩码，确认被阻塞的信号编号。
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