Hello Michael, Here is the update the patch based on all of your review comments except the completion/wait for cleanup since I am worried about outstanding DMAs would prevent vhost from shutting down. I am sending out this for your review, and test it out later.
For error handling, I update macvtap.c so we can discard the desc even in zero-copy case. Signed-off-by: Shirley Ma <[email protected]> --- drivers/vhost/net.c | 42 +++++++++++++++++++++++++++++++++++++++++- drivers/vhost/vhost.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ drivers/vhost/vhost.h | 13 +++++++++++++ 3 files changed, 103 insertions(+), 1 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 2f7c76a..e87a1f8 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -32,6 +32,10 @@ * Using this limit prevents one virtqueue from starving others. */ #define VHOST_NET_WEIGHT 0x80000 +/* MAX number of TX used buffers for outstanding zerocopy */ +#define VHOST_MAX_PEND 128 +#define VHOST_GOODCOPY_LEN PAGE_SIZE + enum { VHOST_NET_VQ_RX = 0, VHOST_NET_VQ_TX = 1, @@ -129,6 +133,7 @@ static void handle_tx(struct vhost_net *net) int err, wmem; size_t hdr_size; struct socket *sock; + struct skb_ubuf_info pend; /* TODO: check that we are running from vhost_worker? */ sock = rcu_dereference_check(vq->private_data, 1); @@ -151,6 +156,10 @@ static void handle_tx(struct vhost_net *net) hdr_size = vq->vhost_hlen; for (;;) { + /* Release DMAs done buffers first */ + if (atomic_read(&vq->refcnt) > VHOST_MAX_PEND) + vhost_zerocopy_signal_used(vq, false); + head = vhost_get_vq_desc(&net->dev, vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in, @@ -166,6 +175,12 @@ static void handle_tx(struct vhost_net *net) set_bit(SOCK_ASYNC_NOSPACE, &sock->flags); break; } + /* If more outstanding DMAs, queue the work */ + if (atomic_read(&vq->refcnt) > VHOST_MAX_PEND) { + tx_poll_start(net, sock); + set_bit(SOCK_ASYNC_NOSPACE, &sock->flags); + break; + } if (unlikely(vhost_enable_notify(vq))) { vhost_disable_notify(vq); continue; @@ -188,6 +203,30 @@ static void handle_tx(struct vhost_net *net) iov_length(vq->hdr, s), hdr_size); break; } + /* use msg_control to pass vhost zerocopy ubuf info to skb */ + if (sock_flag(sock->sk, SOCK_ZEROCOPY)) { + vq->heads[vq->upend_idx].id = head; + if (len < VHOST_GOODCOPY_LEN) + /* copy don't need to wait for DMA done */ + vq->heads[vq->upend_idx].len = + VHOST_DMA_DONE_LEN; + else { + vq->heads[vq->upend_idx].len = len; + pend.callback = vhost_zerocopy_callback; + pend.arg = vq; + pend.desc = vq->upend_idx; + msg.msg_control = &pend; + msg.msg_controllen = sizeof(pend); + } + atomic_inc(&vq->refcnt); + vq->upend_idx = (vq->upend_idx + 1) % UIO_MAXIOV; + /* if upend_idx is full, then wait for free more */ + if (vq->upend_idx == vq->done_idx) { + tx_poll_start(net, sock); + set_bit(SOCK_ASYNC_NOSPACE, &sock->flags); + break; + } + } /* TODO: Check specific error and bomb out unless ENOBUFS? */ err = sock->ops->sendmsg(NULL, sock, &msg, len); if (unlikely(err < 0)) { @@ -198,7 +237,8 @@ static void handle_tx(struct vhost_net *net) if (err != len) pr_debug("Truncated TX packet: " " len %d != %zd\n", err, len); - vhost_add_used_and_signal(&net->dev, vq, head, 0); + if (!sock_flag(sock->sk, SOCK_ZEROCOPY)) + vhost_add_used_and_signal(&net->dev, vq, head, 0); total_len += len; if (unlikely(total_len >= VHOST_NET_WEIGHT)) { vhost_poll_queue(&vq->poll); diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2ab2912..f4c2730 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -174,6 +174,9 @@ static void vhost_vq_reset(struct vhost_dev *dev, vq->call_ctx = NULL; vq->call = NULL; vq->log_ctx = NULL; + vq->upend_idx = 0; + vq->done_idx = 0; + atomic_set(&vq->refcnt, 0); } static int vhost_worker(void *data) @@ -385,16 +388,49 @@ long vhost_dev_reset_owner(struct vhost_dev *dev) return 0; } +/* In case of DMA done not in order in lower device driver for some reason. + * upend_idx is used to track end of used idx, done_idx is used to track head + * of used idx. Once lower device DMA done contiguously, we will signal KVM + * guest used idx. + */ +void vhost_zerocopy_signal_used(struct vhost_virtqueue *vq, bool shutdown) +{ + int i, j = 0; + + for (i = vq->done_idx; i != vq->upend_idx; i = i++ % UIO_MAXIOV) { + if ((vq->heads[i].len == VHOST_DMA_DONE_LEN) || shutdown) { + vq->heads[i].len = VHOST_DMA_CLEAR_LEN; + vhost_add_used_and_signal(vq->dev, vq, + vq->heads[i].id, 0); + ++j; + } else + break; + } + if (j) { + vq->done_idx = i; + atomic_sub(j, &vq->refcnt); + } +} + /* Caller should have device mutex */ void vhost_dev_cleanup(struct vhost_dev *dev) { int i; + unsigned long begin = jiffies; for (i = 0; i < dev->nvqs; ++i) { if (dev->vqs[i].kick && dev->vqs[i].handle_kick) { vhost_poll_stop(&dev->vqs[i].poll); vhost_poll_flush(&dev->vqs[i].poll); } + /* Wait for all lower device DMAs done, then notify virtio_net + * or just notify it without waiting for all DMA done here ? + * in case of DMAs never done for some reason */ + if (atomic_read(&dev->vqs[i].refcnt)) { + /* how long should we wait ? */ + msleep(1000); + vhost_zerocopy_signal_used(&dev->vqs[i], true); + } if (dev->vqs[i].error_ctx) eventfd_ctx_put(dev->vqs[i].error_ctx); if (dev->vqs[i].error) @@ -603,6 +639,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp) mutex_lock(&vq->mutex); + /* clean up lower device outstanding DMAs, before setting ring */ + if (atomic_read(&vq->refcnt)) + vhost_zerocopy_signal_used(vq, true); + switch (ioctl) { case VHOST_SET_VRING_NUM: /* Resizing ring with an active backend? @@ -1416,3 +1456,12 @@ void vhost_disable_notify(struct vhost_virtqueue *vq) vq_err(vq, "Failed to enable notification at %p: %d\n", &vq->used->flags, r); } + +void vhost_zerocopy_callback(struct sk_buff *skb) +{ + int idx = skb_shinfo(skb)->ubuf.desc; + struct vhost_virtqueue *vq = skb_shinfo(skb)->ubuf.arg; + + /* set len = 1 to mark this desc buffers done DMA */ + vq->heads[idx].len = VHOST_DMA_DONE_LEN; +} diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index b3363ae..d0e7ac6 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -13,6 +13,11 @@ #include <linux/virtio_ring.h> #include <asm/atomic.h> +/* This is for zerocopy, used buffer len is set to 1 when lower device DMA + * done */ +#define VHOST_DMA_DONE_LEN 1 +#define VHOST_DMA_CLEAR_LEN 0 + struct vhost_device; struct vhost_work; @@ -108,6 +113,12 @@ struct vhost_virtqueue { /* Log write descriptors */ void __user *log_base; struct vhost_log *log; + /* vhost zerocopy support */ + atomic_t refcnt; /* num of outstanding zerocopy DMAs */ + /* last used idx for outstanding DMA zerocopy buffers */ + int upend_idx; + /* first used idx for DMA done zerocopy buffers */ + int done_idx; }; struct vhost_dev { @@ -154,6 +165,8 @@ bool vhost_enable_notify(struct vhost_virtqueue *); int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, unsigned int log_num, u64 len); +void vhost_zerocopy_callback(struct sk_buff *skb); +void vhost_zerocopy_signal_used(struct vhost_virtqueue *vq, bool shutdown); #define vq_err(vq, fmt, ...) do { \ pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \ -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
