From 8ea8cf89e19aeb596b818ee5f2bec8a8b0586b60 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Fri, 20 May 2011 02:10:54 +0300 Subject: 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: Michael S. Tsirkin Signed-off-by: Rusty Russell --- drivers/vhost/vhost.c | 138 +++++++++++++++++++++++++++++++++++++------------- 1 file changed, 104 insertions(+), 34 deletions(-) (limited to 'drivers/vhost/vhost.c') diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 7aa4eea930f1..ea966b356352 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -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); + } } -- cgit v1.2.3