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vm-virtio: block: Add support for VIRTIO_RING_F_EVENT_IDX

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Permit the guest to suppress interrupts from the host as an
optimisation.

Fixes: #786

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
This commit is contained in:
Rob Bradford 2020-05-15 16:58:31 +01:00 committed by Sebastien Boeuf
parent 5a55fc0737
commit 4366dd92ac
1 changed files with 53 additions and 1 deletions
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54
vm-virtio/src/block.rs
View File

@ -23,6 +23,7 @@ use std::cmp;
use std::convert::TryInto;
use std::fs::{File, Metadata};
use std::io::{self, Read, Seek, SeekFrom, Write};
use std::num::Wrapping;
use std::ops::DerefMut;
use std::os::linux::fs::MetadataExt;
use std::os::unix::io::{AsRawFd, RawFd};
@ -33,6 +34,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Mutex};
use std::thread;
use virtio_bindings::bindings::virtio_blk::*;
use virtio_bindings::bindings::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
use vm_memory::{
ByteValued, Bytes, GuestAddress, GuestAddressSpace, GuestMemory, GuestMemoryAtomic,
GuestMemoryError, GuestMemoryMmap,
@ -604,6 +606,8 @@ struct BlockEpollHandler<T: DiskFile> {
disk_image_id: Vec<u8>,
kill_evt: EventFd,
pause_evt: EventFd,
event_idx: bool,
signalled_used: Option<Wrapping<u16>>,
}
impl<T: DiskFile> BlockEpollHandler<T> {
@ -678,6 +682,25 @@ impl<T: DiskFile> BlockEpollHandler<T> {
Ok(())
}
fn needs_notification(&mut self, mem: &GuestMemoryMmap, used_idx: Wrapping<u16>) -> bool {
if !self.event_idx {
return true;
}
let mut notify = true;
if let Some(old_idx) = self.signalled_used {
if let Some(used_event) = self.queue.get_used_event(&mem) {
if (used_idx - used_event - Wrapping(1u16)) >= (used_idx - old_idx) {
notify = false;
}
}
}
self.signalled_used = Some(used_idx);
notify
}
fn run(
&mut self,
queue_evt: EventFd,
@ -738,6 +761,28 @@ impl<T: DiskFile> BlockEpollHandler<T> {
if let Err(e) = queue_evt.read() {
error!("Failed to get queue event: {:?}", e);
break 'epoll;
} else if self.event_idx {
// vm-virtio's Queue implementation only checks avail_index
// once, so to properly support EVENT_IDX we need to keep
// calling process_queue() until it stops finding new
// requests on the queue.
loop {
if self.process_queue() {
self.queue.update_avail_event(&self.mem.memory());
if self.needs_notification(
&self.mem.memory(),
self.queue.next_used,
) {
if let Err(e) = self.signal_used_queue() {
error!("Failed to signal used queue: {:?}", e);
break 'epoll;
}
}
} else {
break;
}
}
} else if self.process_queue() {
if let Err(e) = self.signal_used_queue() {
error!("Failed to signal used queue: {:?}", e);
@ -934,7 +979,9 @@ impl<T: DiskFile> Block<T> {
);
}
let mut avail_features = (1u64 << VIRTIO_F_VERSION_1) | (1u64 << VIRTIO_BLK_F_FLUSH);
let mut avail_features = (1u64 << VIRTIO_F_VERSION_1)
| (1u64 << VIRTIO_BLK_F_FLUSH)
| (1u64 << VIRTIO_RING_F_EVENT_IDX);
if iommu {
avail_features |= 1u64 << VIRTIO_F_IOMMU_PLATFORM;
@ -1112,6 +1159,9 @@ impl<T: 'static + DiskFile + Send> VirtioDevice for Block<T> {
}
self.queue_evts = Some(tmp_queue_evts);
let event_idx = self.acked_features & 1u64 << VIRTIO_RING_F_EVENT_IDX
== 1u64 << VIRTIO_RING_F_EVENT_IDX;
let mut epoll_threads = Vec::new();
for _ in 0..self.queue_size.len() {
let mut handler = BlockEpollHandler {
@ -1123,6 +1173,8 @@ impl<T: 'static + DiskFile + Send> VirtioDevice for Block<T> {
disk_image_id: disk_image_id.clone(),
kill_evt: kill_evt.try_clone().unwrap(),
pause_evt: pause_evt.try_clone().unwrap(),
event_idx,
signalled_used: None,
};
let queue_evt = queue_evts.remove(0);