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virtio-devices: balloon: add statistics virtqueue support

Browse source 
Implement the virtio balloon statistics virtqueue per the VIRTIO spec,
exposing guest memory statistics through a new /vm.balloon-statistics
API endpoint.

Device layer: add stats virtqueue constants and types, wire up the
stats queue in the balloon handler, implement stats request/response
handlers, and expose a public request_balloon_statistics function.

VMM layer: plumb statistics through device manager, VM, and VMM,
add HTTP and D-Bus API endpoints, add ServiceUnavailable (503) to
api_client, add balloon-statistics subcommand to ch-remote, and add
the endpoint to the OpenAPI spec.

The response includes both guest-reported stats and host-known values
(balloon_actual_bytes, balloon_target_bytes, balloon_total_ram_bytes)
so consumers can understand balloon utilization without querying
/vm.info separately.

Also fixes pre-existing rustfmt issues and adds clippy+rustfmt to the
flake devShell.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Davíð Steinn Geirsson 2026-03-22 10:05:19 +00:00
parent 04311414b6
commit 480bfb7095
13 changed files with 586 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

2
api_client/src/lib.rs
View file

@ -41,6 +41,7 @@ pub enum StatusCode {
TooManyRequests,
InternalServerError,
NotImplemented,
ServiceUnavailable,
Unknown,
}
@ -55,6 +56,7 @@ impl StatusCode {
429 => StatusCode::TooManyRequests,
500 => StatusCode::InternalServerError,
501 => StatusCode::NotImplemented,
503 => StatusCode::ServiceUnavailable,
_ => StatusCode::Unknown,
}
}

9
cloud-hypervisor/src/bin/ch-remote.rs
View file

@ -91,6 +91,7 @@ trait DBusApi1 {
fn vm_boot(&self) -> zbus::Result<()>;
fn vm_coredump(&self, vm_coredump_data: &str) -> zbus::Result<()>;
fn vm_counters(&self) -> zbus::Result<Optional<String>>;
fn vm_balloon_statistics(&self) -> zbus::Result<Optional<String>>;
fn vm_create(&self, vm_config: &str) -> zbus::Result<()>;
fn vm_delete(&self) -> zbus::Result<()>;
fn vm_info(&self) -> zbus::Result<String>;
@ -188,6 +189,10 @@ impl<'a> DBusApi1ProxyBlocking<'a> {
self.print_response(self.vm_counters())
}
fn api_vm_balloon_statistics(&self) -> ApiResult {
self.print_response(self.vm_balloon_statistics())
}
fn api_vm_create(&self, vm_config: &str) -> ApiResult {
self.vm_create(vm_config).map_err(Error::DBusApiClient)
}
@ -295,6 +300,8 @@ fn rest_api_do_command(matches: &ArgMatches, socket: &mut UnixStream) -> ApiResu
Some("counters") => {
simple_api_command(socket, "GET", "counters", None).map_err(Error::HttpApiClient)
}
Some("balloon-statistics") => simple_api_command(socket, "GET", "balloon-statistics", None)
.map_err(Error::HttpApiClient),
Some("ping") => {
simple_api_full_command(socket, "GET", "vmm.ping", None).map_err(Error::HttpApiClient)
}
@ -543,6 +550,7 @@ fn dbus_api_do_command(matches: &ArgMatches, proxy: &DBusApi1ProxyBlocking<'_>)
Some("pause") => proxy.api_vm_pause(),
Some("info") => proxy.api_vm_info(),
Some("counters") => proxy.api_vm_counters(),
Some("balloon-statistics") => proxy.api_vm_balloon_statistics(),
Some("ping") => proxy.api_vmm_ping(),
Some("shutdown") => proxy.api_vm_shutdown(),
Some("resize") => {
@ -1004,6 +1012,7 @@ fn get_cli_commands_sorted() -> Box<[Command]> {
Command::new("add-vsock")
.about("Add vsock device")
.arg(Arg::new("vsock_config").index(1).help(VsockConfig::SYNTAX)),
Command::new("balloon-statistics").about("Balloon statistics from the VM"),
Command::new("boot").about("Boot a created VM"),
Command::new("coredump")
.about("Create a coredump from VM")

17
flake.nix
View file

@ -79,5 +79,22 @@
});
}
);
devShells = forAllSystems (
system:
let
pkgs = nixpkgs.legacyPackages.${system};
inherit (pkgs) lib;
in
{
default = pkgs.mkShell {
inputsFrom = [ self.packages.${system}.cloud-hypervisor ];
nativeBuildInputs = with pkgs; [
clippy
rustfmt
];
};
}
);
};
}

285
virtio-devices/src/balloon.rs
View file

@ -19,7 +19,8 @@ use std::mem::size_of;
use std::os::unix::io::AsRawFd;
use std::result;
use std::sync::atomic::AtomicBool;
use std::sync::{Arc, Barrier};
use std::sync::{Arc, Barrier, Condvar, Mutex};
use std::time::Duration;
use anyhow::anyhow;
use event_monitor::event;
@ -52,18 +53,40 @@ const MIN_NUM_QUEUES: usize = 2;
const INFLATE_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 1;
// Deflate virtio queue event.
const DEFLATE_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 2;
// Stats virtio queue event.
const STATS_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 3;
// Stats request event (triggered by host to request stats from guest).
const STATS_REQUEST_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 5;
// Reporting virtio queue event.
const REPORTING_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 3;
const REPORTING_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 4;
// Stats queue constants.
const STATS_QUEUE_SIZE: u16 = 2;
const STATS_QUEUE_INDEX: usize = 2;
// Size of a PFN in the balloon interface.
const VIRTIO_BALLOON_PFN_SHIFT: u64 = 12;
// Enable the stats virtqueue.
const VIRTIO_BALLOON_F_STATS_VQ: u64 = 1;
// Deflate balloon on OOM
const VIRTIO_BALLOON_F_DEFLATE_ON_OOM: u64 = 2;
// Enable an additional virtqueue to let the guest notify the host about free
// pages.
const VIRTIO_BALLOON_F_REPORTING: u64 = 5;
// Stats tags as defined in the virtio spec.
const VIRTIO_BALLOON_S_SWAP_IN: u16 = 0;
const VIRTIO_BALLOON_S_SWAP_OUT: u16 = 1;
const VIRTIO_BALLOON_S_MAJFLT: u16 = 2;
const VIRTIO_BALLOON_S_MINFLT: u16 = 3;
const VIRTIO_BALLOON_S_MEMFREE: u16 = 4;
const VIRTIO_BALLOON_S_MEMTOT: u16 = 5;
const VIRTIO_BALLOON_S_AVAIL: u16 = 6;
const VIRTIO_BALLOON_S_CACHES: u16 = 7;
const VIRTIO_BALLOON_S_HTLB_PGALLOC: u16 = 8;
const VIRTIO_BALLOON_S_HTLB_PGFAIL: u16 = 9;
#[derive(Error, Debug)]
pub enum Error {
#[error("Guest gave us bad memory addresses.")]
@ -88,6 +111,12 @@ pub enum Error {
QueueAddUsed(#[source] virtio_queue::Error),
#[error("Failed creating an iterator over the queue")]
QueueIterator(#[source] virtio_queue::Error),
#[error("Stats feature not negotiated by guest")]
StatsFeatureNotNegotiated,
#[error("Stats request timed out")]
StatsTimeout,
#[error("Failed to parse stats buffer")]
StatsDescriptorParse,
}
// Got from include/uapi/linux/virtio_balloon.h
@ -150,12 +179,49 @@ const CONFIG_ACTUAL_SIZE: usize = 4;
// SAFETY: it only has data and has no implicit padding.
unsafe impl ByteValued for VirtioBalloonConfig {}
#[derive(Clone, Default, Debug, Serialize, Deserialize)]
pub struct BalloonStatistics {
#[serde(skip_serializing_if = "Option::is_none")]
pub swap_in: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub swap_out: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub major_faults: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub minor_faults: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub free_memory: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub total_memory: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub available_memory: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub disk_caches: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub hugetlb_allocations: Option<u64>,
#[serde(skip_serializing_if = "Option::is_none")]
pub hugetlb_failures: Option<u64>,
}
pub struct BalloonStatsState {
pub stats: Option<BalloonStatistics>,
pub pending: bool,
pub generation: u64,
}
pub type SharedStatsState = Arc<(Mutex<BalloonStatsState>, Condvar)>;
struct BalloonEpollHandler {
mem: GuestMemoryAtomic<GuestMemoryMmap>,
queues: Vec<Queue>,
interrupt_cb: Arc<dyn VirtioInterrupt>,
inflate_queue_evt: EventFd,
deflate_queue_evt: EventFd,
stats_queue_evt: Option<EventFd>,
stats_request_evt: Option<EventFd>,
stats_state: SharedStatsState,
stats_desc_index: Option<u16>,
stats_generation: u64,
reporting_queue_evt: Option<EventFd>,
kill_evt: EventFd,
pause_evt: EventFd,
@ -340,6 +406,107 @@ impl BalloonEpollHandler {
}
}
fn parse_stats_buffer(
memory: &GuestMemoryMmap,
addr: GuestAddress,
len: u32,
) -> result::Result<BalloonStatistics, Error> {
let entry_size = size_of::<u16>() + size_of::<u64>(); // 10 bytes per entry
let mut stats = BalloonStatistics::default();
let mut offset = 0u64;
while offset + entry_size as u64 <= len as u64 {
let tag_addr = addr
.checked_add(offset)
.ok_or(Error::StatsDescriptorParse)?;
let val_addr = addr
.checked_add(offset + size_of::<u16>() as u64)
.ok_or(Error::StatsDescriptorParse)?;
let mut tag_bytes = [0u8; 2];
memory
.read_slice(&mut tag_bytes, tag_addr)
.map_err(|_| Error::StatsDescriptorParse)?;
let tag = u16::from_le_bytes(tag_bytes);
let mut val_bytes = [0u8; 8];
memory
.read_slice(&mut val_bytes, val_addr)
.map_err(|_| Error::StatsDescriptorParse)?;
let val = u64::from_le_bytes(val_bytes);
match tag {
VIRTIO_BALLOON_S_SWAP_IN => stats.swap_in = Some(val),
VIRTIO_BALLOON_S_SWAP_OUT => stats.swap_out = Some(val),
VIRTIO_BALLOON_S_MAJFLT => stats.major_faults = Some(val),
VIRTIO_BALLOON_S_MINFLT => stats.minor_faults = Some(val),
VIRTIO_BALLOON_S_MEMFREE => stats.free_memory = Some(val),
VIRTIO_BALLOON_S_MEMTOT => stats.total_memory = Some(val),
VIRTIO_BALLOON_S_AVAIL => stats.available_memory = Some(val),
VIRTIO_BALLOON_S_CACHES => stats.disk_caches = Some(val),
VIRTIO_BALLOON_S_HTLB_PGALLOC => stats.hugetlb_allocations = Some(val),
VIRTIO_BALLOON_S_HTLB_PGFAIL => stats.hugetlb_failures = Some(val),
_ => {
log::warn!("Unknown balloon stats tag: {tag}");
}
}
offset += entry_size as u64;
}
Ok(stats)
}
fn process_stats_queue(&mut self) -> result::Result<(), Error> {
while let Some(mut desc_chain) =
self.queues[STATS_QUEUE_INDEX].pop_descriptor_chain(self.mem.memory())
{
let desc = desc_chain.next().ok_or(Error::DescriptorChainTooShort)?;
let head_index = desc_chain.head_index();
let parsed = Self::parse_stats_buffer(desc_chain.memory(), desc.addr(), desc.len());
match parsed {
Ok(new_stats) => {
let (mutex, condvar) = self.stats_state.as_ref();
let mut state = mutex.lock().unwrap();
if state.pending && state.generation == self.stats_generation {
state.stats = Some(new_stats);
state.pending = false;
condvar.notify_all();
}
}
Err(e) => {
log::error!("Failed to parse balloon stats buffer: {e:?}");
}
}
// Retain the descriptor index so we can re-use it for the next request.
self.stats_desc_index = Some(head_index);
}
Ok(())
}
fn request_stats(&mut self) -> result::Result<(), Error> {
{
let (mutex, _) = self.stats_state.as_ref();
let state = mutex.lock().unwrap();
self.stats_generation = state.generation;
}
if let Some(head_index) = self.stats_desc_index.take() {
let mem = self.mem.memory();
self.queues[STATS_QUEUE_INDEX]
.add_used(&*mem, head_index, 0)
.map_err(Error::QueueAddUsed)?;
self.signal(VirtioInterruptType::Queue(STATS_QUEUE_INDEX as u16))?;
} else if let Some(desc_chain) =
self.queues[STATS_QUEUE_INDEX].pop_descriptor_chain(self.mem.memory())
{
self.queues[STATS_QUEUE_INDEX]
.add_used(desc_chain.memory(), desc_chain.head_index(), 0)
.map_err(Error::QueueAddUsed)?;
self.signal(VirtioInterruptType::Queue(STATS_QUEUE_INDEX as u16))?;
} else {
log::warn!("Stats queue empty: guest hasn't placed init buffer yet");
}
Ok(())
}
fn run(
&mut self,
paused: &AtomicBool,
@ -348,6 +515,12 @@ impl BalloonEpollHandler {
let mut helper = EpollHelper::new(&self.kill_evt, &self.pause_evt)?;
helper.add_event(self.inflate_queue_evt.as_raw_fd(), INFLATE_QUEUE_EVENT)?;
helper.add_event(self.deflate_queue_evt.as_raw_fd(), DEFLATE_QUEUE_EVENT)?;
if let Some(stats_queue_evt) = self.stats_queue_evt.as_ref() {
helper.add_event(stats_queue_evt.as_raw_fd(), STATS_QUEUE_EVENT)?;
}
if let Some(stats_request_evt) = self.stats_request_evt.as_ref() {
helper.add_event(stats_request_evt.as_raw_fd(), STATS_REQUEST_EVENT)?;
}
if let Some(reporting_queue_evt) = self.reporting_queue_evt.as_ref() {
helper.add_event(reporting_queue_evt.as_raw_fd(), REPORTING_QUEUE_EVENT)?;
}
@ -389,6 +562,40 @@ impl EpollHelperHandler for BalloonEpollHandler {
))
})?;
}
STATS_QUEUE_EVENT => {
if let Some(stats_queue_evt) = self.stats_queue_evt.as_ref() {
stats_queue_evt.read().map_err(|e| {
EpollHelperError::HandleEvent(anyhow!(
"Failed to get stats queue event: {e:?}"
))
})?;
self.process_stats_queue().map_err(|e| {
EpollHelperError::HandleEvent(anyhow!(
"Failed to process stats queue: {e:?}"
))
})?;
} else {
return Err(EpollHelperError::HandleEvent(anyhow!(
"Invalid stats queue event as no eventfd registered"
)));
}
}
STATS_REQUEST_EVENT => {
if let Some(stats_request_evt) = self.stats_request_evt.as_ref() {
stats_request_evt.read().map_err(|e| {
EpollHelperError::HandleEvent(anyhow!(
"Failed to get stats request event: {e:?}"
))
})?;
self.request_stats().map_err(|e| {
EpollHelperError::HandleEvent(anyhow!("Failed to request stats: {e:?}"))
})?;
} else {
return Err(EpollHelperError::HandleEvent(anyhow!(
"Invalid stats request event as no eventfd registered"
)));
}
}
REPORTING_QUEUE_EVENT => {
if let Some(reporting_queue_evt) = self.reporting_queue_evt.as_ref() {
reporting_queue_evt.read().map_err(|e| {
@ -396,7 +603,7 @@ impl EpollHelperHandler for BalloonEpollHandler {
"Failed to get reporting queue event: {e:?}"
))
})?;
self.process_reporting_queue(2).map_err(|e| {
self.process_reporting_queue(3).map_err(|e| {
EpollHelperError::HandleEvent(anyhow!(
"Failed to signal used inflate queue: {e:?}"
))
@ -433,6 +640,8 @@ pub struct Balloon {
seccomp_action: SeccompAction,
exit_evt: EventFd,
interrupt_cb: Option<Arc<dyn VirtioInterrupt>>,
stats_state: SharedStatsState,
stats_request_evt: EventFd,
}
impl Balloon {
@ -458,6 +667,7 @@ impl Balloon {
)
} else {
let mut avail_features = 1u64 << VIRTIO_F_VERSION_1;
avail_features |= 1u64 << VIRTIO_BALLOON_F_STATS_VQ;
if deflate_on_oom {
avail_features |= 1u64 << VIRTIO_BALLOON_F_DEFLATE_ON_OOM;
}
@ -473,6 +683,8 @@ impl Balloon {
(avail_features, 0, config, false)
};
queue_sizes.push(STATS_QUEUE_SIZE);
if free_page_reporting {
queue_sizes.push(REPORTING_QUEUE_SIZE);
}
@ -493,9 +705,32 @@ impl Balloon {
seccomp_action,
exit_evt,
interrupt_cb: None,
stats_state: Arc::new((
Mutex::new(BalloonStatsState {
stats: None,
pending: false,
generation: 0,
}),
Condvar::new(),
)),
stats_request_evt: EventFd::new(libc::EFD_NONBLOCK)
.map_err(|e| io::Error::other(format!("Failed to create stats EventFd: {e}")))?,
})
}
pub fn stats_resources(&self) -> Option<(SharedStatsState, EventFd)> {
if self.common.feature_acked(VIRTIO_BALLOON_F_STATS_VQ) {
Some((
self.stats_state.clone(),
self.stats_request_evt
.try_clone()
.expect("failed to clone stats_request_evt"),
))
} else {
None
}
}
pub fn resize(&mut self, size: u64) -> Result<(), Error> {
self.config.num_pages = (size >> VIRTIO_BALLOON_PFN_SHIFT) as u32;
@ -513,6 +748,11 @@ impl Balloon {
(self.config.actual as u64) << VIRTIO_BALLOON_PFN_SHIFT
}
// Get the target size of the virtio-balloon.
pub fn get_target(&self) -> u64 {
(self.config.num_pages as u64) << VIRTIO_BALLOON_PFN_SHIFT
}
fn state(&self) -> BalloonState {
BalloonState {
avail_features: self.common.avail_features,
@ -606,6 +846,18 @@ impl VirtioDevice for Balloon {
let (_, queue, queue_evt) = queues.remove(0);
virtqueues.push(queue);
let deflate_queue_evt = queue_evt;
let (stats_queue_evt, stats_request_evt) =
if self.common.feature_acked(VIRTIO_BALLOON_F_STATS_VQ) && !queues.is_empty() {
let (_, queue, queue_evt) = queues.remove(0);
virtqueues.push(queue);
let req_evt = self
.stats_request_evt
.try_clone()
.map_err(crate::ActivateError::CloneExitEventFd)?;
(Some(queue_evt), Some(req_evt))
} else {
(None, None)
};
let reporting_queue_evt =
if self.common.feature_acked(VIRTIO_BALLOON_F_REPORTING) && !queues.is_empty() {
let (_, queue, queue_evt) = queues.remove(0);
@ -623,6 +875,11 @@ impl VirtioDevice for Balloon {
interrupt_cb,
inflate_queue_evt,
deflate_queue_evt,
stats_queue_evt,
stats_request_evt,
stats_state: self.stats_state.clone(),
stats_desc_index: None,
stats_generation: 0,
reporting_queue_evt,
kill_evt,
pause_evt,
@ -675,3 +932,25 @@ impl Snapshottable for Balloon {
}
impl Transportable for Balloon {}
impl Migratable for Balloon {}
pub fn request_balloon_statistics(
stats_state: &SharedStatsState,
request_evt: &EventFd,
) -> result::Result<BalloonStatistics, Error> {
let (mutex, condvar) = stats_state.as_ref();
let mut state = mutex.lock().unwrap();
state.generation = state.generation.wrapping_add(1);
let expected_gen = state.generation;
state.pending = true;
state.stats = None;
request_evt.write(1).map_err(Error::EventFdWriteFail)?;
let (state, timeout_result) = condvar
.wait_timeout_while(state, Duration::from_millis(500), |s| {
s.pending && s.generation == expected_gen
})
.unwrap();
if timeout_result.timed_out() || state.generation != expected_gen {
return Err(Error::StatsTimeout);
}
state.stats.clone().ok_or(Error::StatsTimeout)
}

1
virtio-devices/src/lib.rs
View file

@ -39,6 +39,7 @@ use vm_memory::{GuestAddress, GuestMemory};
use vm_virtio::VirtioDeviceType;
pub use self::balloon::Balloon;
pub use self::balloon::BalloonStatistics;
pub use self::block::{Block, BlockState};
pub use self::console::{Console, ConsoleResizer, Endpoint};
pub use self::device::{

10
vmm/src/api/dbus/mod.rs
View file

@ -23,9 +23,9 @@ use super::{ApiAction, ApiRequest};
use crate::api::VmCoredump;
use crate::api::{
AddDisk, Body, VmAddDevice, VmAddFs, VmAddNet, VmAddPmem, VmAddUserDevice, VmAddVdpa,
VmAddVsock, VmBoot, VmCounters, VmCreate, VmDelete, VmInfo, VmPause, VmPowerButton, VmReboot,
VmReceiveMigration, VmRemoveDevice, VmResize, VmResizeZone, VmRestore, VmResume,
VmSendMigration, VmShutdown, VmSnapshot, VmmPing, VmmShutdown,
VmAddVsock, VmBalloonStatistics, VmBoot, VmCounters, VmCreate, VmDelete, VmInfo, VmPause,
VmPowerButton, VmReboot, VmReceiveMigration, VmRemoveDevice, VmResize, VmResizeZone, VmRestore,
VmResume, VmSendMigration, VmShutdown, VmSnapshot, VmmPing, VmmShutdown,
};
use crate::seccomp_filters::{Thread, get_seccomp_filter};
use crate::{Error as VmmError, NetConfig, Result as VmmResult, VmConfig};
@ -200,6 +200,10 @@ impl DBusApi {
self.vm_action(&VmCounters, ()).await
}
async fn vm_balloon_statistics(&self) -> Result<Optional<String>> {
self.vm_action(&VmBalloonStatistics, ()).await
}
async fn vm_create(&self, vm_config: String) -> Result<()> {
let api_sender = self.clone_api_sender().await;
let api_notifier = self.clone_api_notifier()?;

27
vmm/src/api/http/http_endpoint.rs
View file

@ -46,12 +46,14 @@ use crate::api::http::http_endpoint::fds_helper::{attach_fds_to_cfg, attach_fds_
use crate::api::http::{EndpointHandler, HttpError, error_response};
use crate::api::{
AddDisk, ApiAction, ApiError, ApiRequest, NetConfig, VmAddDevice, VmAddFs, VmAddNet, VmAddPmem,
VmAddUserDevice, VmAddVdpa, VmAddVsock, VmBoot, VmConfig, VmCounters, VmDelete, VmNmi, VmPause,
VmPowerButton, VmReboot, VmReceiveMigration, VmRemoveDevice, VmResize, VmResizeDisk,
VmResizeZone, VmRestore, VmResume, VmSendMigration, VmShutdown, VmSnapshot,
VmAddUserDevice, VmAddVdpa, VmAddVsock, VmBalloonStatistics, VmBoot, VmConfig, VmCounters,
VmDelete, VmNmi, VmPause, VmPowerButton, VmReboot, VmReceiveMigration, VmRemoveDevice,
VmResize, VmResizeDisk, VmResizeZone, VmRestore, VmResume, VmSendMigration, VmShutdown,
VmSnapshot,
};
use crate::config::RestoreConfig;
use crate::cpu::Error as CpuError;
use crate::device_manager::DeviceManagerError;
use crate::vm::Error as VmError;
/// Helper module for attaching externally opened FDs to config objects.
@ -485,6 +487,25 @@ impl PutHandler for VmResize {
impl GetHandler for VmResize {}
impl GetHandler for VmBalloonStatistics {
fn handle_request(
&'static self,
api_notifier: EventFd,
api_sender: Sender<ApiRequest>,
) -> std::result::Result<Option<Body>, HttpError> {
self.send(api_notifier, api_sender, ())
.map_err(|e| match e {
ApiError::VmBalloonStatistics(VmError::DeviceManager(
DeviceManagerError::MissingVirtioBalloon,
)) => HttpError::NotFound,
ApiError::VmBalloonStatistics(_) => HttpError::ServiceUnavailable,
_ => HttpError::ApiError(e),
})
}
}
impl PutHandler for VmBalloonStatistics {}
// Special handling for virtio-net devices backed by network FDs.
// See module description for more info.
impl PutHandler for VmRestore {

18
vmm/src/api/http/mod.rs
View file

@ -29,9 +29,9 @@ use self::http_endpoint::{VmActionHandler, VmCreate, VmInfo, VmmPing, VmmShutdow
use crate::api::VmCoredump;
use crate::api::{
AddDisk, ApiError, ApiRequest, VmAddDevice, VmAddFs, VmAddNet, VmAddPmem, VmAddUserDevice,
VmAddVdpa, VmAddVsock, VmBoot, VmCounters, VmDelete, VmNmi, VmPause, VmPowerButton, VmReboot,
VmReceiveMigration, VmRemoveDevice, VmResize, VmResizeDisk, VmResizeZone, VmRestore, VmResume,
VmSendMigration, VmShutdown, VmSnapshot,
VmAddVdpa, VmAddVsock, VmBalloonStatistics, VmBoot, VmCounters, VmDelete, VmNmi, VmPause,
VmPowerButton, VmReboot, VmReceiveMigration, VmRemoveDevice, VmResize, VmResizeDisk,
VmResizeZone, VmRestore, VmResume, VmSendMigration, VmShutdown, VmSnapshot,
};
use crate::landlock::Landlock;
use crate::seccomp_filters::{Thread, get_seccomp_filter};
@ -64,6 +64,10 @@ pub enum HttpError {
#[error("Internal Server Error")]
InternalServerError,
/// Service Unavailable
#[error("Service Unavailable")]
ServiceUnavailable,
/// Error from internal API
#[error("Error from API")]
ApiError(#[source] ApiError),
@ -138,6 +142,10 @@ pub trait EndpointHandler {
error_response(e, StatusCode::BadRequest)
}
Err(e @ HttpError::TooManyRequests) => error_response(e, StatusCode::TooManyRequests),
Err(e @ HttpError::NotFound) => error_response(e, StatusCode::NotFound),
Err(e @ HttpError::ServiceUnavailable) => {
error_response(e, StatusCode::ServiceUnavailable)
}
Err(e) => error_response(e, StatusCode::InternalServerError),
}
}
@ -220,6 +228,10 @@ pub static HTTP_ROUTES: LazyLock<HttpRoutes> = LazyLock::new(|| {
endpoint!("/vm.counters"),
Box::new(VmActionHandler::new(&VmCounters)),
);
r.routes.insert(
endpoint!("/vm.balloon-statistics"),
Box::new(VmActionHandler::new(&VmBalloonStatistics)),
);
r.routes
.insert(endpoint!("/vm.create"), Box::new(VmCreate {}));
r.routes.insert(

83
vmm/src/api/mod.rs
View file

@ -205,6 +205,10 @@ pub enum ApiError {
/// Error triggering NMI
#[error("Error triggering NMI")]
VmNmi(#[source] VmError),
/// Failed to get balloon statistics
#[error("Failed to get balloon statistics")]
VmBalloonStatistics(#[source] VmError),
}
pub type ApiResult<T> = Result<T, ApiError>;
@ -356,6 +360,8 @@ pub trait RequestHandler {
fn vm_counters(&mut self) -> Result<Option<Vec<u8>>, VmError>;
fn vm_balloon_statistics(&mut self) -> Result<Option<Vec<u8>>, VmError>;
fn vm_power_button(&mut self) -> Result<(), VmError>;
fn vm_receive_migration(
@ -872,6 +878,45 @@ impl ApiAction for VmCounters {
}
}
#[derive(Clone, Debug, Serialize)]
pub struct BalloonStatisticsResponse {
#[serde(flatten)]
pub stats: virtio_devices::BalloonStatistics,
pub balloon_actual_bytes: u64,
pub balloon_target_bytes: u64,
pub balloon_total_ram_bytes: u64,
}
pub struct VmBalloonStatistics;
impl ApiAction for VmBalloonStatistics {
type RequestBody = ();
type ResponseBody = Option<Body>;
fn request(&self, _: Self::RequestBody, response_sender: Sender<ApiResponse>) -> ApiRequest {
Box::new(move |vmm| {
info!("API request event: VmBalloonStatistics");
let response = vmm
.vm_balloon_statistics()
.map_err(ApiError::VmBalloonStatistics)
.map(ApiResponsePayload::VmAction);
response_sender
.send(response)
.map_err(VmmError::ApiResponseSend)?;
Ok(false)
})
}
fn send(
&self,
api_evt: EventFd,
api_sender: Sender<ApiRequest>,
data: Self::RequestBody,
) -> ApiResult<Self::ResponseBody> {
get_response_body(self, api_evt, api_sender, data)
}
}
pub struct VmCreate;
impl ApiAction for VmCreate {
@ -1538,3 +1583,41 @@ impl ApiAction for VmNmi {
get_response_body(self, api_evt, api_sender, data)
}
}
#[cfg(test)]
mod tests {
use super::*;
use virtio_devices::BalloonStatistics;
#[test]
fn test_balloon_statistics_response_serialization() {
let response = BalloonStatisticsResponse {
stats: BalloonStatistics {
free_memory: Some(1024),
total_memory: Some(4096),
..Default::default()
},
balloon_actual_bytes: 2048,
balloon_target_bytes: 2048,
balloon_total_ram_bytes: 4096,
};
let json = serde_json::to_value(&response).unwrap();
// Verify flatten works: guest stats appear at top level, not nested
assert_eq!(json["free_memory"], 1024);
assert_eq!(json["total_memory"], 4096);
// Verify new fields are present
assert_eq!(json["balloon_actual_bytes"], 2048);
assert_eq!(json["balloon_target_bytes"], 2048);
assert_eq!(json["balloon_total_ram_bytes"], 4096);
// Verify None fields are omitted (skip_serializing_if works with flatten)
assert!(json.get("swap_in").is_none());
assert!(json.get("major_faults").is_none());
// Verify no nested "stats" key
assert!(json.get("stats").is_none());
}
}

82
vmm/src/api/openapi/cloud-hypervisor.yaml
View file

@ -52,6 +52,22 @@ paths:
schema:
$ref: "#/components/schemas/VmCounters"
/vm.balloon-statistics:
get:
summary: Get balloon statistics from the VM
operationId: vm.balloon-statistics
responses:
200:
description: The balloon statistics
content:
application/json:
schema:
$ref: '#/components/schemas/BalloonStatistics'
404:
description: No balloon device configured
503:
description: Balloon statistics not available
/vm.create:
put:
summary: Create the cloud-hypervisor Virtual Machine (VM) instance. The instance is not booted, only created.
@ -1029,6 +1045,72 @@ components:
default: false
description: Enable guest to report free pages.
BalloonStatistics:
type: object
properties:
swap_in:
description: Amount of memory swapped in (bytes)
type: integer
format: int64
nullable: true
swap_out:
description: Amount of memory swapped out (bytes)
type: integer
format: int64
nullable: true
major_faults:
description: Number of major page faults
type: integer
format: int64
nullable: true
minor_faults:
description: Number of minor page faults
type: integer
format: int64
nullable: true
free_memory:
description: Amount of free memory (bytes)
type: integer
format: int64
nullable: true
total_memory:
description: Total memory available (bytes)
type: integer
format: int64
nullable: true
available_memory:
description: Estimated available memory for new applications (bytes)
type: integer
format: int64
nullable: true
disk_caches:
description: Amount of memory used for disk caches (bytes)
type: integer
format: int64
nullable: true
hugetlb_allocations:
description: Number of successful hugetlb page allocations
type: integer
format: int64
nullable: true
hugetlb_failures:
description: Number of failed hugetlb page allocations
type: integer
format: int64
nullable: true
balloon_actual_bytes:
description: Current balloon size in bytes (guest-confirmed)
type: integer
format: int64
balloon_target_bytes:
description: Target balloon size in bytes (host-requested)
type: integer
format: int64
balloon_total_ram_bytes:
description: Total VM RAM in bytes (includes hotplugged memory)
type: integer
format: int64
FsConfig:
required:
- num_queues

42
vmm/src/device_manager.rs
View file

@ -116,6 +116,7 @@ use vm_migration::{
use vm_virtio::{AccessPlatform, VirtioDeviceType};
use vmm_sys_util::eventfd::EventFd;
use crate::api::BalloonStatisticsResponse;
use crate::console_devices::{ConsoleDeviceError, ConsoleInfo, ConsoleOutput};
use crate::cpu::{CPU_MANAGER_ACPI_SIZE, CpuManager};
use crate::device_tree::{DeviceNode, DeviceTree};
@ -556,6 +557,11 @@ pub enum DeviceManagerError {
#[error("Missing virtio-balloon, can't proceed as expected")]
MissingVirtioBalloon,
#[error("Balloon statistics feature not negotiated by guest")]
VirtioBalloonStatsNotNegotiated,
#[error("Failed to get balloon statistics")]
VirtioBalloonStatistics(#[source] virtio_devices::balloon::Error),
/// Missing virtual IOMMU device
#[error("Missing virtual IOMMU device")]
MissingVirtualIommu,
@ -3882,7 +3888,10 @@ impl DeviceManager {
vfio_container
};
let vfio_device = VfioDevice::new(&device_cfg.path, Arc::clone(&vfio_container) as Arc<dyn VfioOps>)
let vfio_device = VfioDevice::new(
&device_cfg.path,
Arc::clone(&vfio_container) as Arc<dyn VfioOps>,
)
.map_err(DeviceManagerError::VfioCreate)?;
if needs_dma_mapping {
@ -5081,6 +5090,37 @@ impl DeviceManager {
Err(DeviceManagerError::MissingVirtioBalloon)
}
pub fn balloon_statistics(&self) -> DeviceManagerResult<BalloonStatisticsResponse> {
if let Some(balloon) = &self.balloon {
let balloon_locked = balloon.lock().unwrap();
let (stats_state, request_evt) = balloon_locked
.stats_resources()
.ok_or(DeviceManagerError::VirtioBalloonStatsNotNegotiated)?;
let balloon_actual_bytes = balloon_locked.get_actual();
let balloon_target_bytes = balloon_locked.get_target();
// Drop the lock before the blocking stats request
drop(balloon_locked);
let stats =
virtio_devices::balloon::request_balloon_statistics(&stats_state, &request_evt)
.map_err(DeviceManagerError::VirtioBalloonStatistics)?;
let balloon_total_ram_bytes = self.config.lock().unwrap().memory.total_size();
Ok(BalloonStatisticsResponse {
stats,
balloon_actual_bytes,
balloon_target_bytes,
balloon_total_ram_bytes,
})
} else {
Err(DeviceManagerError::MissingVirtioBalloon)
}
}
pub fn balloon_size(&self) -> u64 {
if let Some(balloon) = &self.balloon {
return balloon.lock().unwrap().get_actual();

13
vmm/src/lib.rs
View file

@ -2266,6 +2266,19 @@ impl RequestHandler for Vmm {
}
}
fn vm_balloon_statistics(&mut self) -> result::Result<Option<Vec<u8>>, VmError> {
if let Some(ref mut vm) = self.vm {
let stats = vm.balloon_statistics().inspect_err(|e| {
error!("Error getting balloon statistics: {e:?}");
})?;
serde_json::to_vec(&stats)
.map(Some)
.map_err(VmError::SerializeJson)
} else {
Err(VmError::VmNotRunning)
}
}
fn vm_power_button(&mut self) -> result::Result<(), VmError> {
if let Some(ref mut vm) = self.vm {
vm.power_button()

12
vmm/src/vm.rs
View file

@ -66,9 +66,7 @@ use tracer::trace_scoped;
use vm_device::Bus;
#[cfg(feature = "tdx")]
use vm_memory::{Address, ByteValued, GuestMemoryRegion, ReadVolatile};
use vm_memory::{
Bytes, GuestAddress, GuestAddressSpace, GuestMemoryAtomic, WriteVolatile,
};
use vm_memory::{Bytes, GuestAddress, GuestAddressSpace, GuestMemoryAtomic, WriteVolatile};
use vm_migration::protocol::{MemoryRangeTable, Request, Response};
use vm_migration::{
Migratable, MigratableError, Pausable, Snapshot, Snapshottable, Transportable, snapshot_from_id,
@ -2258,6 +2256,14 @@ impl Vm {
Ok(self.device_manager.lock().unwrap().counters())
}
pub fn balloon_statistics(&self) -> Result<crate::api::BalloonStatisticsResponse> {
self.device_manager
.lock()
.unwrap()
.balloon_statistics()
.map_err(Error::DeviceManager)
}
#[cfg(feature = "tdx")]
fn extract_tdvf_sections(&mut self) -> Result<(Vec<TdvfSection>, bool)> {
use arch::x86_64::tdx::*;