Commit ba7438ae authored by Al Viro's avatar Al Viro
Browse files

vhost: don't bother copying iovecs in handle_rx(), kill memcpy_toiovecend() 



Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 98a527aa

drivers/vhost/net.c

+23 −59
Original line number Diff line number Diff line
@@ -84,10 +84,6 @@ struct vhost_net_ubuf_ref { 


struct vhost_net_virtqueue {

	struct vhost_virtqueue vq;

	/* hdr is used to store the virtio header.

	 * Since each iovec has >= 1 byte length, we never need more than

	 * header length entries to store the header. */

	struct iovec hdr[sizeof(struct virtio_net_hdr_mrg_rxbuf)];

	size_t vhost_hlen;

	size_t sock_hlen;

	/* vhost zerocopy support fields below: */
@@ -235,44 +231,6 @@ static bool vhost_sock_zcopy(struct socket *sock) 
		sock_flag(sock->sk, SOCK_ZEROCOPY);

}



/* Pop first len bytes from iovec. Return number of segments used. */

static int move_iovec_hdr(struct iovec *from, struct iovec *to,

			  size_t len, int iov_count)

{

	int seg = 0;

	size_t size;



	while (len && seg < iov_count) {

		size = min(from->iov_len, len);

		to->iov_base = from->iov_base;

		to->iov_len = size;

		from->iov_len -= size;

		from->iov_base += size;

		len -= size;

		++from;

		++to;

		++seg;

	}

	return seg;

}

/* Copy iovec entries for len bytes from iovec. */

static void copy_iovec_hdr(const struct iovec *from, struct iovec *to,

			   size_t len, int iovcount)

{

	int seg = 0;

	size_t size;



	while (len && seg < iovcount) {

		size = min(from->iov_len, len);

		to->iov_base = from->iov_base;

		to->iov_len = size;

		len -= size;

		++from;

		++to;

		++seg;

	}

}



/* 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
@@ -570,9 +528,9 @@ static void handle_rx(struct vhost_net *net) 
		.msg_controllen = 0,

		.msg_flags = MSG_DONTWAIT,

	};

	struct virtio_net_hdr_mrg_rxbuf hdr = {

		.hdr.flags = 0,

		.hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE

	struct virtio_net_hdr hdr = {

		.flags = 0,

		.gso_type = VIRTIO_NET_HDR_GSO_NONE

	};

	size_t total_len = 0;

	int err, mergeable;
@@ -580,6 +538,7 @@ static void handle_rx(struct vhost_net *net) 
	size_t vhost_hlen, sock_hlen;

	size_t vhost_len, sock_len;

	struct socket *sock;

	struct iov_iter fixup;



	mutex_lock(&vq->mutex);

	sock = vq->private_data;
@@ -624,14 +583,19 @@ static void handle_rx(struct vhost_net *net) 
			break;

		}

		/* We don't need to be notified again. */

		if (unlikely((vhost_hlen)))

			/* Skip header. TODO: support TSO. */

			move_iovec_hdr(vq->iov, nvq->hdr, vhost_hlen, in);

		else

			/* Copy the header for use in VIRTIO_NET_F_MRG_RXBUF:

			 * needed because recvmsg can modify msg_iov. */

			copy_iovec_hdr(vq->iov, nvq->hdr, sock_hlen, in);

		iov_iter_init(&msg.msg_iter, READ, vq->iov, in, sock_len);

		iov_iter_init(&msg.msg_iter, READ, vq->iov, in, vhost_len);

		fixup = msg.msg_iter;

		if (unlikely((vhost_hlen))) {

			/* We will supply the header ourselves

			 * TODO: support TSO.

			 */

			iov_iter_advance(&msg.msg_iter, vhost_hlen);

		} else {

			/* It'll come from socket; we'll need to patch

			 * ->num_buffers over if VIRTIO_NET_F_MRG_RXBUF

			 */

			iov_iter_advance(&fixup, sizeof(hdr));

		}

		err = sock->ops->recvmsg(NULL, sock, &msg,

					 sock_len, MSG_DONTWAIT | MSG_TRUNC);

		/* Userspace might have consumed the packet meanwhile:
@@ -643,18 +607,18 @@ static void handle_rx(struct vhost_net *net) 
			vhost_discard_vq_desc(vq, headcount);

			continue;

		}

		/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */

		if (unlikely(vhost_hlen) &&

		    memcpy_toiovecend(nvq->hdr, (unsigned char *)&hdr, 0,

				      vhost_hlen)) {

		    copy_to_iter(&hdr, sizeof(hdr), &fixup) != sizeof(hdr)) {

			vq_err(vq, "Unable to write vnet_hdr at addr %p\n",

			       vq->iov->iov_base);

			break;

		}

		/* TODO: Should check and handle checksum. */

		/* Supply (or replace) ->num_buffers if VIRTIO_NET_F_MRG_RXBUF

		 * TODO: Should check and handle checksum.

		 */

		if (likely(mergeable) &&

		    memcpy_toiovecend(nvq->hdr, (unsigned char *)&headcount,

				      offsetof(typeof(hdr), num_buffers),

				      sizeof hdr.num_buffers)) {

		    copy_to_iter(&headcount, 2, &fixup) != 2) {

			vq_err(vq, "Failed num_buffers write");

			vhost_discard_vq_desc(vq, headcount);

			break;

include/linux/uio.h

+0 −3
Original line number Diff line number Diff line
@@ -137,7 +137,4 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct io 


int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,

			int offset, int len);

int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,

		      int offset, int len);



#endif

lib/iovec.c

+0 −26
Original line number Diff line number Diff line
@@ -2,32 +2,6 @@ 
#include <linux/export.h>

#include <linux/uio.h>



/*

 *	Copy kernel to iovec. Returns -EFAULT on error.

 */



int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,

		      int offset, int len)

{

	int copy;

	for (; len > 0; ++iov) {

		/* Skip over the finished iovecs */

		if (unlikely(offset >= iov->iov_len)) {

			offset -= iov->iov_len;

			continue;

		}

		copy = min_t(unsigned int, iov->iov_len - offset, len);

		if (copy_to_user(iov->iov_base + offset, kdata, copy))

			return -EFAULT;

		offset = 0;

		kdata += copy;

		len -= copy;

	}



	return 0;

}

EXPORT_SYMBOL(memcpy_toiovecend);



/*

 *	Copy iovec to kernel. Returns -EFAULT on error.

 */