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

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

> +
> +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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel