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Subject[PATCH v4 11/13] xen/pvcalls: implement poll command
Date
For active sockets, check the indexes and use the inflight_conn_req
waitqueue to wait.

For passive sockets if an accept is outstanding
(PVCALLS_FLAG_ACCEPT_INFLIGHT), check if it has been answered by looking
at bedata->rsp[req_id]. If so, return POLLIN. Otherwise use the
inflight_accept_req waitqueue.

If no accepts are inflight, send PVCALLS_POLL to the backend. If we have
outstanding POLL requests awaiting for a response use the inflight_req
waitqueue: inflight_req is awaken when a new response is received; on
wakeup we check whether the POLL response is arrived by looking at the
PVCALLS_FLAG_POLL_RET flag. We set the flag from
pvcalls_front_event_handler, if the response was for a POLL command.

In pvcalls_front_event_handler, get the struct sock_mapping from the
poll id (we previously converted struct sock_mapping* to uint64_t and
used it as id).

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
drivers/xen/pvcalls-front.c | 144 +++++++++++++++++++++++++++++++++++++++++---
drivers/xen/pvcalls-front.h | 3 +
2 files changed, 138 insertions(+), 9 deletions(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 01a5a69..8a90213 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -85,6 +85,8 @@ struct sock_mapping {
* Only one poll operation can be inflight for a given socket.
*/
#define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
+#define PVCALLS_FLAG_POLL_INFLIGHT 1
+#define PVCALLS_FLAG_POLL_RET 2
uint8_t flags;
uint32_t inflight_req_id;
struct sock_mapping *accept_map;
@@ -155,15 +157,32 @@ static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);

req_id = rsp->req_id;
- dst = (uint8_t *)&bedata->rsp[req_id] + sizeof(rsp->req_id);
- src = (uint8_t *)rsp + sizeof(rsp->req_id);
- memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
- /*
- * First copy the rest of the data, then req_id. It is
- * paired with the barrier when accessing bedata->rsp.
- */
- smp_wmb();
- WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
+ if (rsp->cmd == PVCALLS_POLL) {
+ struct sock_mapping *map = (struct sock_mapping *)
+ rsp->u.poll.id;
+
+ set_bit(PVCALLS_FLAG_POLL_RET,
+ (void *)&map->passive.flags);
+ /*
+ * Set RET, then clear INFLIGHT. It pairs with
+ * the checks at the beginning of
+ * pvcalls_front_poll_passive.
+ */
+ smp_wmb();
+ clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+ (void *)&map->passive.flags);
+ } else {
+ dst = (uint8_t *)&bedata->rsp[req_id] +
+ sizeof(rsp->req_id);
+ src = (uint8_t *)rsp + sizeof(rsp->req_id);
+ memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
+ /*
+ * First copy the rest of the data, then req_id. It is
+ * paired with the barrier when accessing bedata->rsp.
+ */
+ smp_wmb();
+ WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
+ }

done = 1;
bedata->ring.rsp_cons++;
@@ -834,6 +853,113 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
return ret;
}

+static unsigned int pvcalls_front_poll_passive(struct file *file,
+ struct pvcalls_bedata *bedata,
+ struct sock_mapping *map,
+ poll_table *wait)
+{
+ int notify, req_id, ret;
+ struct xen_pvcalls_request *req;
+
+ if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+ (void *)&map->passive.flags)) {
+ uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
+
+ if (req_id != PVCALLS_INVALID_ID &&
+ READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
+ return POLLIN | POLLRDNORM;
+
+ poll_wait(file, &map->passive.inflight_accept_req, wait);
+ return 0;
+ }
+
+ if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
+ (void *)&map->passive.flags))
+ return POLLIN | POLLRDNORM;
+
+ /*
+ * First check RET, then INFLIGHT. No barriers necessary to
+ * ensure execution ordering because of the conditional
+ * instructions creating control dependencies.
+ */
+
+ if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+ (void *)&map->passive.flags)) {
+ poll_wait(file, &bedata->inflight_req, wait);
+ return 0;
+ }
+
+ spin_lock(&bedata->socket_lock);
+ ret = get_request(bedata, &req_id);
+ if (ret < 0) {
+ spin_unlock(&bedata->socket_lock);
+ return ret;
+ }
+ req = RING_GET_REQUEST(&bedata->ring, req_id);
+ req->req_id = req_id;
+ req->cmd = PVCALLS_POLL;
+ req->u.poll.id = (uint64_t) map;
+
+ bedata->ring.req_prod_pvt++;
+ RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+ spin_unlock(&bedata->socket_lock);
+ if (notify)
+ notify_remote_via_irq(bedata->irq);
+
+ poll_wait(file, &bedata->inflight_req, wait);
+ return 0;
+}
+
+static unsigned int pvcalls_front_poll_active(struct file *file,
+ struct pvcalls_bedata *bedata,
+ struct sock_mapping *map,
+ poll_table *wait)
+{
+ unsigned int mask = 0;
+ int32_t in_error, out_error;
+ struct pvcalls_data_intf *intf = map->active.ring;
+
+ out_error = intf->out_error;
+ in_error = intf->in_error;
+
+ poll_wait(file, &map->active.inflight_conn_req, wait);
+ if (pvcalls_front_write_todo(map))
+ mask |= POLLOUT | POLLWRNORM;
+ if (pvcalls_front_read_todo(map))
+ mask |= POLLIN | POLLRDNORM;
+ if (in_error != 0 || out_error != 0)
+ mask |= POLLERR;
+
+ return mask;
+}
+
+unsigned int pvcalls_front_poll(struct file *file, struct socket *sock,
+ poll_table *wait)
+{
+ struct pvcalls_bedata *bedata;
+ struct sock_mapping *map;
+ int ret;
+
+ pvcalls_enter;
+ if (!pvcalls_front_dev) {
+ pvcalls_exit;
+ return POLLNVAL;
+ }
+ bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+ map = (struct sock_mapping *) sock->sk->sk_send_head;
+ if (!map) {
+ pvcalls_exit;
+ return POLLNVAL;
+ }
+ if (map->active_socket)
+ ret = pvcalls_front_poll_active(file, bedata, map, wait);
+ else
+ ret = pvcalls_front_poll_passive(file, bedata, map, wait);
+ pvcalls_exit;
+ return ret;
+}
+
static const struct xenbus_device_id pvcalls_front_ids[] = {
{ "pvcalls" },
{ "" }
diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
index de24041..25e05b8 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -20,5 +20,8 @@ int pvcalls_front_recvmsg(struct socket *sock,
struct msghdr *msg,
size_t len,
int flags);
+unsigned int pvcalls_front_poll(struct file *file,
+ struct socket *sock,
+ poll_table *wait);

#endif
--
1.9.1
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