Commit 51b1454f authored by Asias He's avatar Asias He Committed by Will Deacon
Browse files

kvm tools: Use vring_need_event() to determine if interrupt is needed

This patch also fixes fio seq-read hang problem.

   root@guest-kvm:~# cat seq-read.fio

   root@guest-kvm:~# fio seq-read.fio
   random-read: (g=0): rw=read, bs=4K-4K/4K-4K, ioengine=sync, iodepth=1
   Starting 1 process
   Jobs: 1 (f=1): [R] [50.0% done] [0K/0K /s] [0/0 iops] [eta 00m:27s]

Acked-by: default avatarSasha Levin <>
Signed-off-by: default avatarAsias He <>
Signed-off-by: default avatarPekka Enberg <>
parent b4108023
......@@ -22,6 +22,7 @@ struct virt_queue {
/* The last_avail_idx field is an index to ->ring of struct vring_avail.
It's where we assume the next request index is at. */
u16 last_avail_idx;
u16 last_used_signalled;
static inline u16 virt_queue__pop(struct virt_queue *queue)
......@@ -53,13 +54,10 @@ static inline void *guest_pfn_to_host(struct kvm *kvm, u32 pfn)
return guest_flat_to_host(kvm, (unsigned long)pfn << VIRTIO_PCI_QUEUE_ADDR_SHIFT);
static inline int virtio_queue__should_signal(struct virt_queue *vq)
return vring_used_event(&vq->vring) <= vq->vring.used->idx;
struct vring_used_elem *virt_queue__set_used_elem(struct virt_queue *queue, u32 head, u32 len);
bool virtio_queue__should_signal(struct virt_queue *vq);
u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm);
u16 virt_queue__get_inout_iov(struct kvm *kvm, struct virt_queue *queue,
struct iovec in_iov[], struct iovec out_iov[],
......@@ -109,3 +109,19 @@ int virtio__get_dev_specific_field(int offset, bool msix, bool features_hi, u32
bool virtio_queue__should_signal(struct virt_queue *vq)
u16 old_idx, new_idx, event_idx;
old_idx = vq->last_used_signalled;
new_idx = vq->vring.used->idx;
event_idx = vring_used_event(&vq->vring);
if (vring_need_event(event_idx, new_idx, old_idx)) {
vq->last_used_signalled = new_idx;
return true;
return false;
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