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Message-Id: <1501541855-7354-10-git-send-email-sstabellini@kernel.org>
Date: Mon, 31 Jul 2017 15:57:32 -0700
From: Stefano Stabellini <sstabellini@...nel.org>
To: xen-devel@...ts.xen.org
Cc: linux-kernel@...r.kernel.org, sstabellini@...nel.org,
jgross@...e.com, boris.ostrovsky@...cle.com,
Stefano Stabellini <stefano@...reto.com>
Subject: [PATCH v3 10/13] xen/pvcalls: implement recvmsg
Implement recvmsg by copying data from the "in" ring. If not enough data
is available and the recvmsg call is blocking, then wait on the
inflight_conn_req waitqueue. Take the active socket in_mutex so that
only one function can access the ring at any given time.
If no data is available on the ring, rather than returning immediately
or sleep-waiting, spin for up to 5000 cycles. This small optimization
turns out to improve performance and latency significantly.
Signed-off-by: Stefano Stabellini <stefano@...reto.com>
CC: boris.ostrovsky@...cle.com
CC: jgross@...e.com
---
drivers/xen/pvcalls-front.c | 102 ++++++++++++++++++++++++++++++++++++++++++++
drivers/xen/pvcalls-front.h | 4 ++
2 files changed, 106 insertions(+)
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 369acde..635a83a 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -105,6 +105,20 @@ static int pvcalls_front_write_todo(struct sock_mapping *map)
return size - pvcalls_queued(prod, cons, size);
}
+static bool pvcalls_front_read_todo(struct sock_mapping *map)
+{
+ struct pvcalls_data_intf *intf = map->active.ring;
+ RING_IDX cons, prod;
+ int32_t error;
+
+ cons = intf->in_cons;
+ prod = intf->in_prod;
+ error = intf->in_error;
+ return (error != 0 ||
+ pvcalls_queued(prod, cons,
+ XEN_FLEX_RING_SIZE(intf->ring_order)) != 0);
+}
+
static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
{
struct xenbus_device *dev = dev_id;
@@ -434,6 +448,94 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
return tot_sent;
}
+static int __read_ring(struct pvcalls_data_intf *intf,
+ struct pvcalls_data *data,
+ struct iov_iter *msg_iter,
+ size_t len, int flags)
+{
+ RING_IDX cons, prod, size, masked_prod, masked_cons;
+ RING_IDX array_size = XEN_FLEX_RING_SIZE(intf->ring_order);
+ int32_t error;
+
+ cons = intf->in_cons;
+ prod = intf->in_prod;
+ error = intf->in_error;
+ /* get pointers before reading from the ring */
+ virt_rmb();
+ if (error < 0)
+ return error;
+
+ size = pvcalls_queued(prod, cons, array_size);
+ masked_prod = pvcalls_mask(prod, array_size);
+ masked_cons = pvcalls_mask(cons, array_size);
+
+ if (size == 0)
+ return 0;
+
+ if (len > size)
+ len = size;
+
+ if (masked_prod > masked_cons) {
+ copy_to_iter(data->in + masked_cons, len, msg_iter);
+ } else {
+ if (len > (array_size - masked_cons)) {
+ copy_to_iter(data->in + masked_cons,
+ array_size - masked_cons, msg_iter);
+ copy_to_iter(data->in,
+ len - (array_size - masked_cons),
+ msg_iter);
+ } else {
+ copy_to_iter(data->in + masked_cons, len, msg_iter);
+ }
+ }
+ /* read data from the ring before increasing the index */
+ virt_mb();
+ if (!(flags & MSG_PEEK))
+ intf->in_cons += len;
+
+ return len;
+}
+
+int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+ int flags)
+{
+ struct pvcalls_bedata *bedata;
+ int ret = -EAGAIN;
+ struct sock_mapping *map;
+
+ if (!pvcalls_front_dev)
+ return -ENOTCONN;
+ bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+ map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+ if (!map)
+ return -ENOTSOCK;
+
+ if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
+ return -EOPNOTSUPP;
+
+ mutex_lock(&map->active.in_mutex);
+ if (len > XEN_FLEX_RING_SIZE(map->active.ring->ring_order))
+ len = XEN_FLEX_RING_SIZE(map->active.ring->ring_order);
+
+ while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
+ wait_event_interruptible(map->active.inflight_conn_req,
+ pvcalls_front_read_todo(map));
+ }
+ ret = __read_ring(map->active.ring, &map->active.data,
+ &msg->msg_iter, len, flags);
+
+ if (ret > 0)
+ notify_remote_via_irq(map->active.irq);
+ if (ret == 0)
+ ret = -EAGAIN;
+ if (ret == -ENOTCONN)
+ ret = 0;
+
+ mutex_unlock(&map->active.in_mutex);
+ return ret;
+}
+
int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
{
struct pvcalls_bedata *bedata;
diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
index d937c24..de24041 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -16,5 +16,9 @@ int pvcalls_front_accept(struct socket *sock,
int pvcalls_front_sendmsg(struct socket *sock,
struct msghdr *msg,
size_t len);
+int pvcalls_front_recvmsg(struct socket *sock,
+ struct msghdr *msg,
+ size_t len,
+ int flags);
#endif
--
1.9.1
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