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Re: [Xen-devel] [PATCH v4 04/13] xen/pvcalls: implement socket command and handle events





+
+static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
+{
+       *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
+       if (RING_FULL(&bedata->ring) ||
+           READ_ONCE(bedata->rsp[*req_id].req_id) != PVCALLS_INVALID_ID)
+               return -EAGAIN;
+       return 0;
+}
+
  static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
  {
+       struct xenbus_device *dev = dev_id;
+       struct pvcalls_bedata *bedata;
+       struct xen_pvcalls_response *rsp;
+       uint8_t *src, *dst;
+       int req_id = 0, more = 0, done = 0;
+
+       if (dev == NULL)
+               return IRQ_HANDLED;
+
+       pvcalls_enter;
+       bedata = dev_get_drvdata(&dev->dev);
+       if (bedata == NULL) {
+               pvcalls_exit;
+               return IRQ_HANDLED;
+       }
+
+again:
+       while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
+               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);
+
+               done = 1;
+               bedata->ring.rsp_cons++;
+       }
+
+       RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
+       if (more)
+               goto again;
+       if (done)
+               wake_up(&bedata->inflight_req);
+       pvcalls_exit;
        return IRQ_HANDLED;
  }
+int pvcalls_front_socket(struct socket *sock)
+{
+       struct pvcalls_bedata *bedata;
+       struct sock_mapping *map = NULL;
+       struct xen_pvcalls_request *req;
+       int notify, req_id, ret;
+
+       pvcalls_enter;


Can you define enter/exit macros with parentheses (i.e. "pvcalls_enter/exit()')?


+       if (!pvcalls_front_dev) {
+               pvcalls_exit;
+               return -EACCES;
+       }
+       /*
+        * PVCalls only supports domain AF_INET,
+        * type SOCK_STREAM and protocol 0 sockets for now.
+        *
+        * Check socket type here, AF_INET and protocol checks are done
+        * by the caller.
+        */
+       if (sock->type != SOCK_STREAM) {
+               pvcalls_exit;
+               return -ENOTSUPP;
+       }


This can be done without entering pvcalls. I think you can enter pvcalls at least right before grabbing socket lock (you may need to move dev_get_drvdata() lower).

(possibly in later patches too)


+
+       bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+       map = kzalloc(sizeof(*map), GFP_KERNEL);
+       if (map == NULL) {
+               pvcalls_exit;
+               return -ENOMEM;
+       }
+
+       spin_lock(&bedata->socket_lock);
+
+       ret = get_request(bedata, &req_id);
+       if (ret < 0) {
+               kfree(map);
+               spin_unlock(&bedata->socket_lock);
+               pvcalls_exit;
+               return ret;
+       }
+
+       /*
+        * sock->sk->sk_send_head is not used for ip sockets: reuse the
+        * field to store a pointer to the struct sock_mapping
+        * corresponding to the socket. This way, we can easily get the
+        * struct sock_mapping from the struct socket.
+        */
+       sock->sk->sk_send_head = (void *)map;
+       list_add_tail(&map->list, &bedata->socket_mappings);
+
+       req = RING_GET_REQUEST(&bedata->ring, req_id);
+       req->req_id = req_id;
+       req->cmd = PVCALLS_SOCKET;
+       req->u.socket.id = (uint64_t) map;
+       req->u.socket.domain = AF_INET;
+       req->u.socket.type = SOCK_STREAM;
+       req->u.socket.protocol = IPPROTO_IP;
+
+       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);
+
+       wait_event(bedata->inflight_req,
+                  READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
+
+       ret = bedata->rsp[req_id].ret;
+       /* read ret, then set this rsp slot to be reused */
+       smp_mb();
+       WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);

Now that I looked at what *_ONCE macros do I am not sure this is needed, given the smp_mb() above. In pvcalls_front_event_handler() too. And, in fact, in get_request() as well.

(Again, this will probably be also applicable to subsequent patches)

-boris

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