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Message-Id: <1423032009-18367-17-git-send-email-viro@ZenIV.linux.org.uk>
Date: Wed, 4 Feb 2015 06:40:08 +0000
From: Al Viro <viro@...IV.linux.org.uk>
To: David Miller <davem@...emloft.net>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: [PATCH v3 17/18] vhost: don't bother copying iovecs in handle_rx(), kill memcpy_toiovecend()
From: Al Viro <viro@...iv.linux.org.uk>
Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: kvm@...r.kernel.org
Cc: virtualization@...ts.linux-foundation.org
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
drivers/vhost/net.c | 82 +++++++++++++++--------------------------------------
include/linux/uio.h | 3 --
lib/iovec.c | 26 -----------------
3 files changed, 23 insertions(+), 88 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index d86cc9b..e022cc4 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -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;
diff --git a/include/linux/uio.h b/include/linux/uio.h
index af3439f..02bd8a9 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -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
diff --git a/lib/iovec.c b/lib/iovec.c
index 4a90875..d8f17a9 100644
--- a/lib/iovec.c
+++ b/lib/iovec.c
@@ -3,32 +3,6 @@
#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.
*/
--
2.1.4
--
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