Implement support for using receive buffers less than the maximum
packet size by merging the smaller buffers together as needed.
Signed-off-by: Mark McLoughlin <[EMAIL PROTECTED]>
Cc: Herbert Xu <[EMAIL PROTECTED]>
---
Documentation/lguest/lguest.c | 98 +++++++++++++++++++++++++++++++++-------
1 files changed, 81 insertions(+), 17 deletions(-)
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 2ddf0c6..da934c2 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -68,6 +68,8 @@ typedef uint8_t u8;
#define DEVICE_PAGES 256
/* This will occupy 3 pages: it must be a power of 2. */
#define VIRTQUEUE_NUM 256
+/* The largest MAX_SKB_FRAGS pages supported. */
+#define NET_MAX_RECV_PAGES 18
/*L:120 verbose is both a global flag and a macro. The C preprocessor allows
* this, and although I wouldn't recommend it, it works quite nicely here. */
@@ -970,16 +972,15 @@ static void handle_net_output(int fd, struct virtqueue
*vq, bool timeout)
}
}
-/* This is where we handle a packet coming in from the tun device to our
- * Guest. */
-static bool handle_tun_input(int fd, struct device *dev)
+/* Network receive buffers are odd creatures; the Guest usually gives us single
+ * page buffers and - if we're handling big packets - we use multiple buffers
per
+ * packet. */
+static unsigned int get_net_recv_head(struct device *dev, struct iovec *iov,
+ unsigned int *in_num)
{
- unsigned int head, in_num, out_num;
- int len;
- struct iovec iov[dev->vq->vring.num];
+ unsigned int head, out_num;
- /* First we need a network buffer from the Guests's recv virtqueue. */
- head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
+ head = get_vq_desc(dev->vq, iov, &out_num, in_num);
if (head == dev->vq->vring.num) {
/* Now, it's expected that if we try to send a packet too
* early, the Guest won't be ready yet. Wait until the device
@@ -989,23 +990,85 @@ static bool handle_tun_input(int fd, struct device *dev)
/* Now tell it we want to know if new things appear. */
dev->vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
wmb();
-
- /* We'll turn this back on if input buffers are registered. */
- return false;
} else if (out_num)
errx(1, "Output buffers in network recv queue?");
+ return head;
+}
+
+/* Here we add used recv buffers to the used queue but, also, return unused
+ * buffers to the avail queue. */
+static void add_net_recv_used(struct device *dev, unsigned int *heads,
+ int *bufsizes, int nheads, int used_len)
+{
+ int len, idx;
+
+ /* Add the buffers we've actually used to the used queue */
+ len = idx = 0;
+ while (len < used_len) {
+ add_used(dev->vq, heads[idx], used_len, idx);
+ len += bufsizes[idx++];
+ }
+
+ /* Return the rest of them back to the avail queue */
+ lg_last_avail(dev->vq) -= nheads - idx;
+ dev->vq->inflight -= nheads - idx;
+
+ /* Finally, tell the other side */
+ flush_used(dev->vq, idx);
+}
+
+/* This is where we handle a packet coming in from the tun device to our
+ * Guest. */
+static bool handle_tun_input(int fd, struct device *dev)
+{
+ struct iovec iov[dev->vq->vring.num];
+ unsigned int heads[NET_MAX_RECV_PAGES];
+ int bufsizes[NET_MAX_RECV_PAGES];
+ int nheads, len, iovcnt;
+
+ nheads = len = iovcnt = 0;
+
+ /* First we need enough network buffers from the Guests's recv
+ * virtqueue for the largest possible packet. */
+ while (len < (getpagesize() * NET_MAX_RECV_PAGES)) {
+ unsigned int in_num;
+
+ heads[nheads] = get_net_recv_head(dev, &iov[iovcnt], &in_num);
+ if (heads[nheads] == dev->vq->vring.num) {
+ /* It's all our nothing - give these back again */
+ lg_last_avail(dev->vq) -= nheads;
+ dev->vq->inflight -= nheads;
+
+ /* We'll turn this back on if input buffers are
+ * registered. */
+ return false;
+ }
+
+ bufsizes[nheads] = 0;
+ while (in_num--)
+ bufsizes[nheads] += iov[iovcnt++].iov_len;
+
+ /* Enforce a minimum of a page per buffer */
+ if (bufsizes[nheads] < getpagesize())
+ errx(1, "Network receive buffer too small");
+
+ len += bufsizes[nheads++];
+ }
+
/* Read the packet from the device directly into the Guest's buffer. */
- len = readv(dev->fd, iov, in_num);
+ len = readv(dev->fd, iov, iovcnt);
if (len <= 0)
err(1, "reading network");
- /* Tell the Guest about the new packet. */
- add_used_and_trigger(fd, dev->vq, head, len);
+ /* Return unused buffers to the recv queue */
+ add_net_recv_used(dev, heads, bufsizes, nheads, len);
+
+ /* Fire in the hole ! */
+ trigger_irq(fd, dev->vq);
- verbose("tun input packet len %i [%02x %02x] (%s)\n", len,
- ((u8 *)iov[1].iov_base)[0], ((u8 *)iov[1].iov_base)[1],
- head != dev->vq->vring.num ? "sent" : "discarded");
+ verbose("tun input packet len %i [%02x %02x] sent\n", len,
+ ((u8 *)iov[0].iov_base)[10], ((u8 *)iov[0].iov_base)[11]);
/* All good. */
return true;
@@ -1561,6 +1624,7 @@ static void setup_tun_net(char *arg)
add_feature(dev, VIRTIO_NET_F_HOST_TSO4);
add_feature(dev, VIRTIO_NET_F_HOST_TSO6);
add_feature(dev, VIRTIO_NET_F_HOST_ECN);
+ add_feature(dev, VIRTIO_NET_F_MRG_RXBUF);
set_config(dev, sizeof(conf), &conf);
/* We don't need the socket any more; setup is done. */
--
1.5.4.3
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