When discarding descriptors with IN_ORDER, we should rewind next_avail_head otherwise it would run out of sync with last_avail_idx. This would cause driver to report "id X is not a head".

Fixing this by returning the number of descriptors that is used for each buffer via vhost_get_vq_desc_n() so caller can use the value while discarding descriptors.

Fixes: 67a873df0c41 ("vhost: basic in order support") Cc: stable@vger.kernel.org Signed-off-by: Jason Wang jasowang@redhat.com --- Changes since V1: - Add the function document - Tweak the variable name --- drivers/vhost/net.c | 53 ++++++++++++++++++------------ drivers/vhost/vhost.c | 76 +++++++++++++++++++++++++++++++++++-------- drivers/vhost/vhost.h | 10 +++++- 3 files changed, 103 insertions(+), 36 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 35ded4330431..8f7f50acb6d6 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -592,14 +592,15 @@ static void vhost_net_busy_poll(struct vhost_net *net, static int vhost_net_tx_get_vq_desc(struct vhost_net *net, struct vhost_net_virtqueue *tnvq, unsigned int *out_num, unsigned int *in_num, - struct msghdr *msghdr, bool *busyloop_intr) + struct msghdr *msghdr, bool *busyloop_intr, + unsigned int *ndesc) { struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX]; struct vhost_virtqueue *rvq = &rnvq->vq; struct vhost_virtqueue *tvq = &tnvq->vq;

- int r = vhost_get_vq_desc(tvq, tvq->iov, ARRAY_SIZE(tvq->iov), - out_num, in_num, NULL, NULL); + int r = vhost_get_vq_desc_n(tvq, tvq->iov, ARRAY_SIZE(tvq->iov), + out_num, in_num, NULL, NULL, ndesc);

if (r == tvq->num && tvq->busyloop_timeout) { /* Flush batched packets first */ @@ -610,8 +611,8 @@ static int vhost_net_tx_get_vq_desc(struct vhost_net *net,

vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, false);

- r = vhost_get_vq_desc(tvq, tvq->iov, ARRAY_SIZE(tvq->iov), - out_num, in_num, NULL, NULL); + r = vhost_get_vq_desc_n(tvq, tvq->iov, ARRAY_SIZE(tvq->iov), + out_num, in_num, NULL, NULL, ndesc); }

return r; @@ -642,12 +643,14 @@ static int get_tx_bufs(struct vhost_net *net, struct vhost_net_virtqueue *nvq, struct msghdr *msg, unsigned int *out, unsigned int *in, - size_t *len, bool *busyloop_intr) + size_t *len, bool *busyloop_intr, + unsigned int *ndesc) { struct vhost_virtqueue *vq = &nvq->vq; int ret;

- ret = vhost_net_tx_get_vq_desc(net, nvq, out, in, msg, busyloop_intr); + ret = vhost_net_tx_get_vq_desc(net, nvq, out, in, msg, + busyloop_intr, ndesc);

if (ret < 0 || ret == vq->num) return ret; @@ -766,6 +769,7 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) int sent_pkts = 0; bool sock_can_batch = (sock->sk->sk_sndbuf == INT_MAX); bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER); + unsigned int ndesc = 0;

do { bool busyloop_intr = false; @@ -774,7 +778,7 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) vhost_tx_batch(net, nvq, sock, &msg);

head = get_tx_bufs(net, nvq, &msg, &out, &in, &len, - &busyloop_intr); + &busyloop_intr, &ndesc); /* On error, stop handling until the next kick. */ if (unlikely(head < 0)) break; @@ -806,7 +810,7 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) goto done; } else if (unlikely(err != -ENOSPC)) { vhost_tx_batch(net, nvq, sock, &msg); - vhost_discard_vq_desc(vq, 1); + vhost_discard_vq_desc(vq, 1, ndesc); vhost_net_enable_vq(net, vq); break; } @@ -829,7 +833,7 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) err = sock->ops->sendmsg(sock, &msg, len); if (unlikely(err < 0)) { if (err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS) { - vhost_discard_vq_desc(vq, 1); + vhost_discard_vq_desc(vq, 1, ndesc); vhost_net_enable_vq(net, vq); break; } @@ -868,6 +872,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) int err; struct vhost_net_ubuf_ref *ubufs; struct ubuf_info_msgzc *ubuf; + unsigned int ndesc = 0; bool zcopy_used; int sent_pkts = 0;

@@ -879,7 +884,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)

busyloop_intr = false; head = get_tx_bufs(net, nvq, &msg, &out, &in, &len, - &busyloop_intr); + &busyloop_intr, &ndesc); /* On error, stop handling until the next kick. */ if (unlikely(head < 0)) break; @@ -941,7 +946,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN; } if (retry) { - vhost_discard_vq_desc(vq, 1); + vhost_discard_vq_desc(vq, 1, ndesc); vhost_net_enable_vq(net, vq); break; } @@ -1045,11 +1050,12 @@ static int get_rx_bufs(struct vhost_net_virtqueue *nvq, unsigned *iovcount, struct vhost_log *log, unsigned *log_num, - unsigned int quota) + unsigned int quota, + unsigned int *ndesc) { struct vhost_virtqueue *vq = &nvq->vq; bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER); - unsigned int out, in; + unsigned int out, in, desc_num, n = 0; int seg = 0; int headcount = 0; unsigned d; @@ -1064,9 +1070,9 @@ static int get_rx_bufs(struct vhost_net_virtqueue *nvq, r = -ENOBUFS; goto err; } - r = vhost_get_vq_desc(vq, vq->iov + seg, - ARRAY_SIZE(vq->iov) - seg, &out, - &in, log, log_num); + r = vhost_get_vq_desc_n(vq, vq->iov + seg, + ARRAY_SIZE(vq->iov) - seg, &out, + &in, log, log_num, &desc_num); if (unlikely(r < 0)) goto err;

@@ -1093,6 +1099,7 @@ static int get_rx_bufs(struct vhost_net_virtqueue *nvq, ++headcount; datalen -= len; seg += in; + n += desc_num; }

*iovcount = seg; @@ -1113,9 +1120,11 @@ static int get_rx_bufs(struct vhost_net_virtqueue *nvq, nheads[0] = headcount; }

+ *ndesc = n; + return headcount; err: - vhost_discard_vq_desc(vq, headcount); + vhost_discard_vq_desc(vq, headcount, n); return r; }

@@ -1151,6 +1160,7 @@ static void handle_rx(struct vhost_net *net) struct iov_iter fixup; __virtio16 num_buffers; int recv_pkts = 0; + unsigned int ndesc;

mutex_lock_nested(&vq->mutex, VHOST_NET_VQ_RX); sock = vhost_vq_get_backend(vq); @@ -1182,7 +1192,8 @@ static void handle_rx(struct vhost_net *net) headcount = get_rx_bufs(nvq, vq->heads + count, vq->nheads + count, vhost_len, &in, vq_log, &log, - likely(mergeable) ? UIO_MAXIOV : 1); + likely(mergeable) ? UIO_MAXIOV : 1, + &ndesc); /* On error, stop handling until the next kick. */ if (unlikely(headcount < 0)) goto out; @@ -1228,7 +1239,7 @@ static void handle_rx(struct vhost_net *net) if (unlikely(err != sock_len)) { pr_debug("Discarded rx packet: " " len %d, expected %zd\n", err, sock_len); - vhost_discard_vq_desc(vq, headcount); + vhost_discard_vq_desc(vq, headcount, ndesc); continue; } /* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */ @@ -1252,7 +1263,7 @@ static void handle_rx(struct vhost_net *net) copy_to_iter(&num_buffers, sizeof num_buffers, &fixup) != sizeof num_buffers) { vq_err(vq, "Failed num_buffers write"); - vhost_discard_vq_desc(vq, headcount); + vhost_discard_vq_desc(vq, headcount, ndesc); goto out; } nvq->done_idx += headcount; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 8570fdf2e14a..a78226b37739 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2792,18 +2792,34 @@ static int get_indirect(struct vhost_virtqueue *vq, return 0; }

-/* This looks in the virtqueue and for the first available buffer, and converts - * it to an iovec for convenient access. Since descriptors consist of some - * number of output then some number of input descriptors, it's actually two - * iovecs, but we pack them into one and note how many of each there were. +/** + * vhost_get_vq_desc_n - Fetch the next available descriptor chain and build iovecs + * @vq: target virtqueue + * @iov: array that receives the scatter/gather segments + * @iov_size: capacity of @iov in elements + * @out_num: the number of output segments + * @in_num: the number of input segments + * @log: optional array to record addr/len for each writable segment; NULL if unused + * @log_num: optional output; number of entries written to @log when provided + * @ndesc: optional output; number of descriptors consumed from the available ring + * (useful for rollback via vhost_discard_vq_desc) * - * This function returns the descriptor number found, or vq->num (which is - * never a valid descriptor number) if none was found. A negative code is - * returned on error. */ -int vhost_get_vq_desc(struct vhost_virtqueue *vq, - struct iovec iov[], unsigned int iov_size, - unsigned int *out_num, unsigned int *in_num, - struct vhost_log *log, unsigned int *log_num) + * Extracts one available descriptor chain from @vq and translates guest addresses + * into host iovecs. + * + * On success, advances @vq->last_avail_idx by 1 and @vq->next_avail_head by the + * number of descriptors consumed (also stored via @ndesc when non-NULL). + * + * Return: + * - head index in [0, @vq->num) on success; + * - @vq->num if no descriptor is currently available; + * - negative errno on failure + */ +int vhost_get_vq_desc_n(struct vhost_virtqueue *vq, + struct iovec iov[], unsigned int iov_size, + unsigned int *out_num, unsigned int *in_num, + struct vhost_log *log, unsigned int *log_num, + unsigned int *ndesc) { bool in_order = vhost_has_feature(vq, VIRTIO_F_IN_ORDER); struct vring_desc desc; @@ -2921,17 +2937,49 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, vq->last_avail_idx++; vq->next_avail_head += c;

+ if (ndesc) + *ndesc = c; + /* 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; } +EXPORT_SYMBOL_GPL(vhost_get_vq_desc_n); + +/* This looks in the virtqueue and for the first available buffer, and converts + * it to an iovec for convenient access. Since descriptors consist of some + * number of output then some number of input descriptors, it's actually two + * iovecs, but we pack them into one and note how many of each there were. + * + * This function returns the descriptor number found, or vq->num (which is + * never a valid descriptor number) if none was found. A negative code is + * returned on error. + */ +int vhost_get_vq_desc(struct vhost_virtqueue *vq, + struct iovec iov[], unsigned int iov_size, + unsigned int *out_num, unsigned int *in_num, + struct vhost_log *log, unsigned int *log_num) +{ + return vhost_get_vq_desc_n(vq, iov, iov_size, out_num, in_num, + log, log_num, NULL); +} EXPORT_SYMBOL_GPL(vhost_get_vq_desc);

-/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */ -void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n) +/** + * vhost_discard_vq_desc - Reverse the effect of vhost_get_vq_desc_n() + * @vq: target virtqueue + * @nbufs: number of buffers to roll back + * @ndesc: number of descriptors to roll back + * + * Rewinds the internal consumer cursors after a failed attempt to use buffers + * returned by vhost_get_vq_desc_n(). + */ +void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int nbufs, + unsigned int ndesc) { - vq->last_avail_idx -= n; + vq->next_avail_head -= ndesc; + vq->last_avail_idx -= nbufs; } EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index 621a6d9a8791..b49f08e4a1b4 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -230,7 +230,15 @@ int vhost_get_vq_desc(struct vhost_virtqueue *, struct iovec iov[], unsigned int iov_size, unsigned int *out_num, unsigned int *in_num, struct vhost_log *log, unsigned int *log_num); -void vhost_discard_vq_desc(struct vhost_virtqueue *, int n); + +int vhost_get_vq_desc_n(struct vhost_virtqueue *vq, + struct iovec iov[], unsigned int iov_size, + unsigned int *out_num, unsigned int *in_num, + struct vhost_log *log, unsigned int *log_num, + unsigned int *ndesc); + +void vhost_discard_vq_desc(struct vhost_virtqueue *, int nbuf, + unsigned int ndesc);

bool vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work); bool vhost_vq_has_work(struct vhost_virtqueue *vq);