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Message-ID: <018b3547-f0b8-8b1b-84b2-525fefafdace@oracle.com>
Date: Wed, 26 Jul 2017 19:23:39 -0400
From: Boris Ostrovsky <boris.ostrovsky@...cle.com>
To: Stefano Stabellini <sstabellini@...nel.org>,
xen-devel@...ts.xen.org
Cc: linux-kernel@...r.kernel.org, jgross@...e.com,
Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v2 10/13] xen/pvcalls: implement poll command
On 07/25/2017 05:22 PM, Stefano Stabellini wrote:
> For active sockets, check the indexes and use the inflight_conn_req
> waitqueue to wait.
>
> For passive sockets, send PVCALLS_POLL to the backend. Use the
> inflight_accept_req waitqueue if an accept is outstanding. Otherwise 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 socket pointer from the
> poll id (we previously converted struct socket* to uint64_t and used it
> as id).
>
> Signed-off-by: Stefano Stabellini <stefano@...reto.com>
> CC: boris.ostrovsky@...cle.com
> CC: jgross@...e.com
> ---
> drivers/xen/pvcalls-front.c | 134 ++++++++++++++++++++++++++++++++++++++++----
> drivers/xen/pvcalls-front.h | 3 +
> 2 files changed, 126 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> index b4ca569..833b717 100644
> --- a/drivers/xen/pvcalls-front.c
> +++ b/drivers/xen/pvcalls-front.c
> @@ -130,17 +130,35 @@ 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;
> - src = (uint8_t *)&bedata->rsp[req_id];
> - src += sizeof(rsp->req_id);
> - dst = (uint8_t *)rsp;
> - dst += 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 socket *sock = (struct socket *) rsp->u.poll.id;
> + struct sock_mapping *map =
> + (struct sock_mapping *)
> + READ_ONCE(sock->sk->sk_send_head);
> +
> + 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();
virt_wmb() (here, below, and I think I saw it somewhere else)
> + clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
> + (void *)&map->passive.flags);
> + } else {
> + src = (uint8_t *)&bedata->rsp[req_id];
> + src += sizeof(rsp->req_id);
> + dst = (uint8_t *)rsp;
> + dst += 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++;
> @@ -707,6 +725,100 @@ 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;
> + struct xen_pvcalls_request *req;
> +
> + if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> + (void *)&map->passive.flags)) {
> + 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;
> +
> + /*
> + * 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->pvcallss_lock);
> + 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) {
> + spin_unlock(&bedata->pvcallss_lock);
> + return -EAGAIN;
> + }
> + req = RING_GET_REQUEST(&bedata->ring, req_id);
> + req->req_id = req_id;
> + req->cmd = PVCALLS_POLL;
> + req->u.poll.id = (uint64_t) map->sock;
> +
> + bedata->ring.req_prod_pvt++;
> + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
> + spin_unlock(&bedata->pvcallss_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;
> +
> + if (!pvcalls_front_dev)
> + return POLLNVAL;
> + bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> +
> + map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
> + if (!map)
> + return POLLNVAL;
> + if (map->active_socket)
> + return pvcalls_front_poll_active(file, bedata, map, wait);
> + else
> + return pvcalls_front_poll_passive(file, bedata, map, wait);
> +}
All other routines return an int (0 or error code). Shouldn't they all
have the same return type? (In fact, where are all these routines called
from?)
-boris
> +
> 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
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