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SubjectRe: [PATCH v4 04/13] xen/pvcalls: implement socket command and handle events
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> +
> +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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