Commit 8ea8cf89 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Rusty Russell

vhost: support event index

Support the new event index feature. When acked,
utilize it to reduce the # of interrupts sent to the guest.
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent a5c262c5
......@@ -144,7 +144,7 @@ static void handle_tx(struct vhost_net *net)
}
mutex_lock(&vq->mutex);
vhost_disable_notify(vq);
vhost_disable_notify(&net->dev, vq);
if (wmem < sock->sk->sk_sndbuf / 2)
tx_poll_stop(net);
......@@ -166,8 +166,8 @@ static void handle_tx(struct vhost_net *net)
set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
break;
}
if (unlikely(vhost_enable_notify(vq))) {
vhost_disable_notify(vq);
if (unlikely(vhost_enable_notify(&net->dev, vq))) {
vhost_disable_notify(&net->dev, vq);
continue;
}
break;
......@@ -315,7 +315,7 @@ static void handle_rx(struct vhost_net *net)
return;
mutex_lock(&vq->mutex);
vhost_disable_notify(vq);
vhost_disable_notify(&net->dev, vq);
vhost_hlen = vq->vhost_hlen;
sock_hlen = vq->sock_hlen;
......@@ -334,10 +334,10 @@ static void handle_rx(struct vhost_net *net)
break;
/* OK, now we need to know about added descriptors. */
if (!headcount) {
if (unlikely(vhost_enable_notify(vq))) {
if (unlikely(vhost_enable_notify(&net->dev, vq))) {
/* They have slipped one in as we were
* doing that: check again. */
vhost_disable_notify(vq);
vhost_disable_notify(&net->dev, vq);
continue;
}
/* Nothing new? Wait for eventfd to tell us
......
......@@ -49,7 +49,7 @@ static void handle_vq(struct vhost_test *n)
return;
mutex_lock(&vq->mutex);
vhost_disable_notify(vq);
vhost_disable_notify(&n->dev, vq);
for (;;) {
head = vhost_get_vq_desc(&n->dev, vq, vq->iov,
......@@ -61,8 +61,8 @@ static void handle_vq(struct vhost_test *n)
break;
/* Nothing new? Wait for eventfd to tell us they refilled. */
if (head == vq->num) {
if (unlikely(vhost_enable_notify(vq))) {
vhost_disable_notify(vq);
if (unlikely(vhost_enable_notify(&n->dev, vq))) {
vhost_disable_notify(&n->dev, vq);
continue;
}
break;
......
......@@ -37,6 +37,9 @@ enum {
VHOST_MEMORY_F_LOG = 0x1,
};
#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
#define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
{
......@@ -161,6 +164,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq->last_avail_idx = 0;
vq->avail_idx = 0;
vq->last_used_idx = 0;
vq->signalled_used = 0;
vq->signalled_used_valid = false;
vq->used_flags = 0;
vq->log_used = false;
vq->log_addr = -1ull;
......@@ -489,16 +494,17 @@ static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
return 1;
}
static int vq_access_ok(unsigned int num,
static int vq_access_ok(struct vhost_dev *d, unsigned int num,
struct vring_desc __user *desc,
struct vring_avail __user *avail,
struct vring_used __user *used)
{
size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
access_ok(VERIFY_READ, avail,
sizeof *avail + num * sizeof *avail->ring) &&
sizeof *avail + num * sizeof *avail->ring + s) &&
access_ok(VERIFY_WRITE, used,
sizeof *used + num * sizeof *used->ring);
sizeof *used + num * sizeof *used->ring + s);
}
/* Can we log writes? */
......@@ -514,9 +520,11 @@ int vhost_log_access_ok(struct vhost_dev *dev)
/* Verify access for write logging. */
/* Caller should have vq mutex and device mutex */
static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
void __user *log_base)
{
struct vhost_memory *mp;
size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
mp = rcu_dereference_protected(vq->dev->memory,
lockdep_is_held(&vq->mutex));
......@@ -524,15 +532,15 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
(!vq->log_used || log_access_ok(log_base, vq->log_addr,
sizeof *vq->used +
vq->num * sizeof *vq->used->ring));
vq->num * sizeof *vq->used->ring + s));
}
/* Can we start vq? */
/* Caller should have vq mutex and device mutex */
int vhost_vq_access_ok(struct vhost_virtqueue *vq)
{
return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
vq_log_access_ok(vq, vq->log_base);
return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
vq_log_access_ok(vq->dev, vq, vq->log_base);
}
static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
......@@ -577,6 +585,7 @@ static int init_used(struct vhost_virtqueue *vq,
if (r)
return r;
vq->signalled_used_valid = false;
return get_user(vq->last_used_idx, &used->idx);
}
......@@ -674,7 +683,7 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
* If it is not, we don't as size might not have been setup.
* We will verify when backend is configured. */
if (vq->private_data) {
if (!vq_access_ok(vq->num,
if (!vq_access_ok(d, vq->num,
(void __user *)(unsigned long)a.desc_user_addr,
(void __user *)(unsigned long)a.avail_user_addr,
(void __user *)(unsigned long)a.used_user_addr)) {
......@@ -818,7 +827,7 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
vq = d->vqs + i;
mutex_lock(&vq->mutex);
/* If ring is inactive, will check when it's enabled. */
if (vq->private_data && !vq_log_access_ok(vq, base))
if (vq->private_data && !vq_log_access_ok(d, vq, base))
r = -EFAULT;
else
vq->log_base = base;
......@@ -1219,6 +1228,10 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
/* On success, increment avail index. */
vq->last_avail_idx++;
/* Assume notifications from guest are disabled at this point,
* if they aren't we would need to update avail_event index. */
BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
return head;
}
......@@ -1267,6 +1280,12 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
eventfd_signal(vq->log_ctx, 1);
}
vq->last_used_idx++;
/* If the driver never bothers to signal in a very long while,
* used index might wrap around. If that happens, invalidate
* signalled_used index we stored. TODO: make sure driver
* signals at least once in 2^16 and remove this. */
if (unlikely(vq->last_used_idx == vq->signalled_used))
vq->signalled_used_valid = false;
return 0;
}
......@@ -1275,6 +1294,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
unsigned count)
{
struct vring_used_elem __user *used;
u16 old, new;
int start;
start = vq->last_used_idx % vq->num;
......@@ -1292,7 +1312,14 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
((void __user *)used - (void __user *)vq->used),
count * sizeof *used);
}
vq->last_used_idx += count;
old = vq->last_used_idx;
new = (vq->last_used_idx += count);
/* If the driver never bothers to signal in a very long while,
* used index might wrap around. If that happens, invalidate
* signalled_used index we stored. TODO: make sure driver
* signals at least once in 2^16 and remove this. */
if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
vq->signalled_used_valid = false;
return 0;
}
......@@ -1331,29 +1358,47 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
return r;
}
/* This actually signals the guest, using eventfd. */
void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
{
__u16 flags;
__u16 old, new, event;
bool v;
/* Flush out used index updates. This is paired
* with the barrier that the Guest executes when enabling
* interrupts. */
smp_mb();
if (__get_user(flags, &vq->avail->flags)) {
vq_err(vq, "Failed to get flags");
return;
if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
unlikely(vq->avail_idx == vq->last_avail_idx))
return true;
if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
__u16 flags;
if (__get_user(flags, &vq->avail->flags)) {
vq_err(vq, "Failed to get flags");
return true;
}
return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
}
old = vq->signalled_used;
v = vq->signalled_used_valid;
new = vq->signalled_used = vq->last_used_idx;
vq->signalled_used_valid = true;
/* If they don't want an interrupt, don't signal, unless empty. */
if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
(vq->avail_idx != vq->last_avail_idx ||
!vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
return;
if (unlikely(!v))
return true;
if (get_user(event, vhost_used_event(vq))) {
vq_err(vq, "Failed to get used event idx");
return true;
}
return vring_need_event(event, new, old);
}
/* This actually signals the guest, using eventfd. */
void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
{
/* Signal the Guest tell them we used something up. */
if (vq->call_ctx)
if (vq->call_ctx && vhost_notify(dev, vq))
eventfd_signal(vq->call_ctx, 1);
}
......@@ -1376,7 +1421,7 @@ void vhost_add_used_and_signal_n(struct vhost_dev *dev,
}
/* OK, now we need to know about added descriptors. */
bool vhost_enable_notify(struct vhost_virtqueue *vq)
bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
{
u16 avail_idx;
int r;
......@@ -1384,11 +1429,34 @@ bool vhost_enable_notify(struct vhost_virtqueue *vq)
if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
return false;
vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
r = put_user(vq->used_flags, &vq->used->flags);
if (r) {
vq_err(vq, "Failed to enable notification at %p: %d\n",
&vq->used->flags, r);
return false;
if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
r = put_user(vq->used_flags, &vq->used->flags);
if (r) {
vq_err(vq, "Failed to enable notification at %p: %d\n",
&vq->used->flags, r);
return false;
}
} else {
r = put_user(vq->avail_idx, vhost_avail_event(vq));
if (r) {
vq_err(vq, "Failed to update avail event index at %p: %d\n",
vhost_avail_event(vq), r);
return false;
}
}
if (unlikely(vq->log_used)) {
void __user *used;
/* Make sure data is seen before log. */
smp_wmb();
used = vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX) ?
&vq->used->flags : vhost_avail_event(vq);
/* Log used flags or event index entry write. Both are 16 bit
* fields. */
log_write(vq->log_base, vq->log_addr +
(used - (void __user *)vq->used),
sizeof(u16));
if (vq->log_ctx)
eventfd_signal(vq->log_ctx, 1);
}
/* They could have slipped one in as we were doing that: make
* sure it's written, then check again. */
......@@ -1404,15 +1472,17 @@ bool vhost_enable_notify(struct vhost_virtqueue *vq)
}
/* We don't need to be notified again. */
void vhost_disable_notify(struct vhost_virtqueue *vq)
void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
{
int r;
if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
return;
vq->used_flags |= VRING_USED_F_NO_NOTIFY;
r = put_user(vq->used_flags, &vq->used->flags);
if (r)
vq_err(vq, "Failed to enable notification at %p: %d\n",
&vq->used->flags, r);
if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
r = put_user(vq->used_flags, &vq->used->flags);
if (r)
vq_err(vq, "Failed to enable notification at %p: %d\n",
&vq->used->flags, r);
}
}
......@@ -84,6 +84,12 @@ struct vhost_virtqueue {
/* Used flags */
u16 used_flags;
/* Last used index value we have signalled on */
u16 signalled_used;
/* Last used index value we have signalled on */
bool signalled_used_valid;
/* Log writes to used structure. */
bool log_used;
u64 log_addr;
......@@ -149,8 +155,8 @@ void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
struct vring_used_elem *heads, unsigned count);
void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
void vhost_disable_notify(struct vhost_virtqueue *);
bool vhost_enable_notify(struct vhost_virtqueue *);
void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
unsigned int log_num, u64 len);
......@@ -162,11 +168,12 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
} while (0)
enum {
VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) |
(1 << VIRTIO_RING_F_INDIRECT_DESC) |
(1 << VHOST_F_LOG_ALL) |
(1 << VHOST_NET_F_VIRTIO_NET_HDR) |
(1 << VIRTIO_NET_F_MRG_RXBUF),
VHOST_FEATURES = (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
(1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
(1ULL << VIRTIO_RING_F_EVENT_IDX) |
(1ULL << VHOST_F_LOG_ALL) |
(1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
(1ULL << VIRTIO_NET_F_MRG_RXBUF),
};
static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
......
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