2 files changed, 138 insertions, 9 deletions

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 24ffdc90e217..c7d4251c3678 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -83,6 +83,8 @@ 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;
@@ -154,15 +156,32 @@ again:
                 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();
-                bedata->rsp[req_id].req_id = rsp->req_id;
+                if (rsp->cmd == PVCALLS_POLL) {
+                        struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
+                                                   rsp->u.poll.id;
+
+                        clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+                                  (void *)&map->passive.flags);
+                        /*
+                         * clear INFLIGHT, then set RET. It pairs with
+                         * the checks at the beginning of
+                         * pvcalls_front_poll_passive.
+                         */
+                        smp_wmb();
+                        set_bit(PVCALLS_FLAG_POLL_RET,
+                                (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();
+                        bedata->rsp[req_id].req_id = req_id;
+                }
 
                 done = 1;
                 bedata->ring.rsp_cons++;
@@ -846,6 +865,113 @@ received:
         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 = (uintptr_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 de24041e9a86..25e05b8f2d72 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