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vm-virtio: block: Ensure backing file consistency

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Correctly implement the virtio specification by setting the writeback
field on the request based on the algorithm in the spec.

TEST=Boot with hypervisor-firmware with CH in verbose mode. See info
level messages saying cache mode is writethrough in firmware (no support
for flush or WCE). Once in the Linux kernel see messages that mode is
writeback.

Fixes: #1216
Fixes: #680

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
This commit is contained in:
Rob Bradford 2020-05-20 17:04:52 +01:00 committed by Samuel Ortiz
parent dc66eee8f0
commit 9101bdd7a9
1 changed files with 33 additions and 2 deletions
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35
vm-virtio/src/block.rs
View File

@ -610,6 +610,7 @@ struct BlockEpollHandler<T: DiskFile> {
kill_evt: EventFd,
pause_evt: EventFd,
event_idx: bool,
writeback: Arc<AtomicBool>,
}
impl<T: DiskFile> BlockEpollHandler<T> {
@ -622,7 +623,9 @@ impl<T: DiskFile> BlockEpollHandler<T> {
for avail_desc in queue.iter(&mem) {
let len;
match Request::parse(&avail_desc, &mem) {
Ok(request) => {
Ok(mut request) => {
request.set_writeback(self.writeback.load(Ordering::SeqCst));
let mut disk_image_locked = self.disk_image.lock().unwrap();
let mut disk_image = disk_image_locked.deref_mut();
let status = match request.execute(
@ -931,6 +934,7 @@ pub struct Block<T: DiskFile> {
pause_evt: Option<EventFd>,
paused: Arc<AtomicBool>,
queue_size: Vec<u16>,
writeback: Arc<AtomicBool>,
}
#[derive(Serialize, Deserialize)]
@ -966,7 +970,8 @@ impl<T: DiskFile> Block<T> {
let mut avail_features = (1u64 << VIRTIO_F_VERSION_1)
| (1u64 << VIRTIO_BLK_F_FLUSH)
| (1u64 << VIRTIO_RING_F_EVENT_IDX);
| (1u64 << VIRTIO_RING_F_EVENT_IDX)
| (1u64 << VIRTIO_BLK_F_CONFIG_WCE);
if iommu {
avail_features |= 1u64 << VIRTIO_F_IOMMU_PLATFORM;
@ -979,6 +984,7 @@ impl<T: DiskFile> Block<T> {
let disk_nsectors = disk_size / SECTOR_SIZE;
let mut config = VirtioBlockConfig {
capacity: disk_nsectors,
writeback: 1,
..Default::default()
};
@ -1002,6 +1008,7 @@ impl<T: DiskFile> Block<T> {
pause_evt: None,
paused: Arc::new(AtomicBool::new(false)),
queue_size: vec![queue_size; num_queues],
writeback: Arc::new(AtomicBool::new(true)),
})
}
@ -1024,6 +1031,27 @@ impl<T: DiskFile> Block<T> {
Ok(())
}
fn update_writeback(&mut self) {
// Use writeback from config if VIRTIO_BLK_F_CONFIG_WCE
let writeback =
if self.acked_features & 1 << VIRTIO_BLK_F_CONFIG_WCE == 1 << VIRTIO_BLK_F_CONFIG_WCE {
self.config.writeback == 1
} else {
// Else check if VIRTIO_BLK_F_FLUSH negotiated
self.acked_features & 1 << VIRTIO_BLK_F_FLUSH == 1 << VIRTIO_BLK_F_FLUSH
};
info!(
"Changing cache mode to {}",
if writeback {
"writeback"
} else {
"writethrough"
}
);
self.writeback.store(writeback, Ordering::SeqCst);
}
}
impl<T: DiskFile> Drop for Block<T> {
@ -1085,6 +1113,7 @@ impl<T: 'static + DiskFile + Send> VirtioDevice for Block<T> {
}
let (_, right) = config_slice.split_at_mut(offset as usize);
right.copy_from_slice(&data[..]);
self.update_writeback();
}
fn activate(
@ -1146,6 +1175,7 @@ impl<T: 'static + DiskFile + Send> VirtioDevice for Block<T> {
let event_idx = self.acked_features & 1u64 << VIRTIO_RING_F_EVENT_IDX
== 1u64 << VIRTIO_RING_F_EVENT_IDX;
self.update_writeback();
let mut epoll_threads = Vec::new();
for _ in 0..self.queue_size.len() {
@ -1159,6 +1189,7 @@ impl<T: 'static + DiskFile + Send> VirtioDevice for Block<T> {
kill_evt: kill_evt.try_clone().unwrap(),
pause_evt: pause_evt.try_clone().unwrap(),
event_idx,
writeback: self.writeback.clone(),
};
handler.queue.set_event_idx(event_idx);