From 97bc3633bec7ed0fdfbda6b9cf86c51e4f58f8e2 Mon Sep 17 00:00:00 2001 From: Shirley Ma Date: Wed, 6 Jul 2011 12:26:11 +0000 Subject: [PATCH] macvtap: macvtapTX zero-copy support Only 128 bytes is copied, the rest of data is DMA mapped directly from userspace. Signed-off-by: Shirley Ma Signed-off-by: David S. Miller --- drivers/net/macvtap.c | 132 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 121 insertions(+), 11 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index ecee0fe65a97..ab96c319a240 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -60,6 +60,7 @@ static struct proto macvtap_proto = { */ static dev_t macvtap_major; #define MACVTAP_NUM_DEVS 65536 +#define GOODCOPY_LEN 128 static struct class *macvtap_class; static struct cdev macvtap_cdev; @@ -340,6 +341,7 @@ static int macvtap_open(struct inode *inode, struct file *file) { struct net *net = current->nsproxy->net_ns; struct net_device *dev = dev_get_by_index(net, iminor(inode)); + struct macvlan_dev *vlan = netdev_priv(dev); struct macvtap_queue *q; int err; @@ -369,6 +371,16 @@ static int macvtap_open(struct inode *inode, struct file *file) q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP; q->vnet_hdr_sz = sizeof(struct virtio_net_hdr); + /* + * so far only KVM virtio_net uses macvtap, enable zero copy between + * guest kernel and host kernel when lower device supports zerocopy + */ + if (vlan) { + if ((vlan->lowerdev->features & NETIF_F_HIGHDMA) && + (vlan->lowerdev->features & NETIF_F_SG)) + sock_set_flag(&q->sk, SOCK_ZEROCOPY); + } + err = macvtap_set_queue(dev, file, q); if (err) sock_put(&q->sk); @@ -433,6 +445,80 @@ static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad, return skb; } +/* set skb frags from iovec, this can move to core network code for reuse */ +static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from, + int offset, size_t count) +{ + int len = iov_length(from, count) - offset; + int copy = skb_headlen(skb); + int size, offset1 = 0; + int i = 0; + skb_frag_t *f; + + /* Skip over from offset */ + while (count && (offset >= from->iov_len)) { + offset -= from->iov_len; + ++from; + --count; + } + + /* copy up to skb headlen */ + while (count && (copy > 0)) { + size = min_t(unsigned int, copy, from->iov_len - offset); + if (copy_from_user(skb->data + offset1, from->iov_base + offset, + size)) + return -EFAULT; + if (copy > size) { + ++from; + --count; + } + copy -= size; + offset1 += size; + offset = 0; + } + + if (len == offset1) + return 0; + + while (count--) { + struct page *page[MAX_SKB_FRAGS]; + int num_pages; + unsigned long base; + + len = from->iov_len - offset1; + if (!len) { + offset1 = 0; + ++from; + continue; + } + base = (unsigned long)from->iov_base + offset1; + size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT; + num_pages = get_user_pages_fast(base, size, 0, &page[i]); + if ((num_pages != size) || + (num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags)) + /* put_page is in skb free */ + return -EFAULT; + skb->data_len += len; + skb->len += len; + skb->truesize += len; + atomic_add(len, &skb->sk->sk_wmem_alloc); + while (len) { + f = &skb_shinfo(skb)->frags[i]; + f->page = page[i]; + f->page_offset = base & ~PAGE_MASK; + f->size = min_t(int, len, PAGE_SIZE - f->page_offset); + skb_shinfo(skb)->nr_frags++; + /* increase sk_wmem_alloc */ + base += f->size; + len -= f->size; + i++; + } + offset1 = 0; + ++from; + } + return 0; +} + /* * macvtap_skb_from_vnet_hdr and macvtap_skb_to_vnet_hdr should * be shared with the tun/tap driver. @@ -517,16 +603,18 @@ static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb, /* Get packet from user space buffer */ -static ssize_t macvtap_get_user(struct macvtap_queue *q, - const struct iovec *iv, size_t count, - int noblock) +static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, + const struct iovec *iv, unsigned long total_len, + size_t count, int noblock) { struct sk_buff *skb; struct macvlan_dev *vlan; - size_t len = count; + unsigned long len = total_len; int err; struct virtio_net_hdr vnet_hdr = { 0 }; int vnet_hdr_len = 0; + int copylen; + bool zerocopy = false; if (q->flags & IFF_VNET_HDR) { vnet_hdr_len = q->vnet_hdr_sz; @@ -554,12 +642,31 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, if (unlikely(len < ETH_HLEN)) goto err; - skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, len, vnet_hdr.hdr_len, - noblock, &err); + if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) + zerocopy = true; + + if (zerocopy) { + /* There are 256 bytes to be copied in skb, so there is enough + * room for skb expand head in case it is used. + * The rest buffer is mapped from userspace. + */ + copylen = vnet_hdr.hdr_len; + if (!copylen) + copylen = GOODCOPY_LEN; + } else + copylen = len; + + skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen, + vnet_hdr.hdr_len, noblock, &err); if (!skb) goto err; - err = skb_copy_datagram_from_iovec(skb, 0, iv, vnet_hdr_len, len); + if (zerocopy) { + err = zerocopy_sg_from_iovec(skb, iv, vnet_hdr_len, count); + skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY; + } else + err = skb_copy_datagram_from_iovec(skb, 0, iv, vnet_hdr_len, + len); if (err) goto err_kfree; @@ -575,13 +682,16 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, rcu_read_lock_bh(); vlan = rcu_dereference_bh(q->vlan); + /* copy skb_ubuf_info for callback when skb has no error */ + if (zerocopy) + skb_shinfo(skb)->destructor_arg = m->msg_control; if (vlan) macvlan_start_xmit(skb, vlan->dev); else kfree_skb(skb); rcu_read_unlock_bh(); - return count; + return total_len; err_kfree: kfree_skb(skb); @@ -603,8 +713,8 @@ static ssize_t macvtap_aio_write(struct kiocb *iocb, const struct iovec *iv, ssize_t result = -ENOLINK; struct macvtap_queue *q = file->private_data; - result = macvtap_get_user(q, iv, iov_length(iv, count), - file->f_flags & O_NONBLOCK); + result = macvtap_get_user(q, NULL, iv, iov_length(iv, count), count, + file->f_flags & O_NONBLOCK); return result; } @@ -817,7 +927,7 @@ static int macvtap_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *m, size_t total_len) { struct macvtap_queue *q = container_of(sock, struct macvtap_queue, sock); - return macvtap_get_user(q, m->msg_iov, total_len, + return macvtap_get_user(q, m, m->msg_iov, total_len, m->msg_iovlen, m->msg_flags & MSG_DONTWAIT); } -- 2.30.2