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xen/pvcalls: implement sendmsg

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Send data to an active socket by copying data to the "out" ring. Take
the active socket out_mutex so that only one function can access the
ring at any given time.

If not enough room 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 significantly.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
Stefano Stabellini 2017-10-30 15:40:59 -07:00 committed by Boris Ostrovsky
parent 9774c6cca2
commit 45ddce214a
2 changed files with 124 additions and 0 deletions
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121
drivers/xen/pvcalls-front.c
View file

@ -29,6 +29,7 @@
#define PVCALLS_INVALID_ID UINT_MAX
#define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
#define PVCALLS_NR_RSP_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
#define PVCALLS_FRONT_MAX_SPIN 5000
struct pvcalls_bedata {
struct xen_pvcalls_front_ring ring;
@ -99,6 +100,23 @@ static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
return 0;
}
static bool pvcalls_front_write_todo(struct sock_mapping *map)
{
struct pvcalls_data_intf *intf = map->active.ring;
RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
int32_t error;
error = intf->out_error;
if (error == -ENOTCONN)
return false;
if (error != 0)
return true;
cons = intf->out_cons;
prod = intf->out_prod;
return !!(size - pvcalls_queued(prod, cons, size));
}
static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
{
struct xenbus_device *dev = dev_id;
@ -363,6 +381,109 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
return ret;
}
static int __write_ring(struct pvcalls_data_intf *intf,
struct pvcalls_data *data,
struct iov_iter *msg_iter,
int len)
{
RING_IDX cons, prod, size, masked_prod, masked_cons;
RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
int32_t error;
error = intf->out_error;
if (error < 0)
return error;
cons = intf->out_cons;
prod = intf->out_prod;
/* read indexes before continuing */
virt_mb();
size = pvcalls_queued(prod, cons, array_size);
if (size >= array_size)
return -EINVAL;
if (len > array_size - size)
len = array_size - size;
masked_prod = pvcalls_mask(prod, array_size);
masked_cons = pvcalls_mask(cons, array_size);
if (masked_prod < masked_cons) {
len = copy_from_iter(data->out + masked_prod, len, msg_iter);
} else {
if (len > array_size - masked_prod) {
int ret = copy_from_iter(data->out + masked_prod,
array_size - masked_prod, msg_iter);
if (ret != array_size - masked_prod) {
len = ret;
goto out;
}
len = ret + copy_from_iter(data->out, len - ret, msg_iter);
} else {
len = copy_from_iter(data->out + masked_prod, len, msg_iter);
}
}
out:
/* write to ring before updating pointer */
virt_wmb();
intf->out_prod += len;
return len;
}
int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
size_t len)
{
struct pvcalls_bedata *bedata;
struct sock_mapping *map;
int sent, tot_sent = 0;
int count = 0, flags;
flags = msg->msg_flags;
if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
return -EOPNOTSUPP;
pvcalls_enter();
if (!pvcalls_front_dev) {
pvcalls_exit();
return -ENOTCONN;
}
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
map = (struct sock_mapping *) sock->sk->sk_send_head;
if (!map) {
pvcalls_exit();
return -ENOTSOCK;
}
mutex_lock(&map->active.out_mutex);
if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
mutex_unlock(&map->active.out_mutex);
pvcalls_exit();
return -EAGAIN;
}
if (len > INT_MAX)
len = INT_MAX;
again:
count++;
sent = __write_ring(map->active.ring,
&map->active.data, &msg->msg_iter,
len);
if (sent > 0) {
len -= sent;
tot_sent += sent;
notify_remote_via_irq(map->active.irq);
}
if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
goto again;
if (sent < 0)
tot_sent = sent;
mutex_unlock(&map->active.out_mutex);
pvcalls_exit();
return tot_sent;
}
int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
{
struct pvcalls_bedata *bedata;

3
drivers/xen/pvcalls-front.h
View file

@ -13,5 +13,8 @@ int pvcalls_front_listen(struct socket *sock, int backlog);
int pvcalls_front_accept(struct socket *sock,
struct socket *newsock,
int flags);
int pvcalls_front_sendmsg(struct socket *sock,
struct msghdr *msg,
size_t len);
#endif