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SubjectRe: [PATCH v3 05/13] xen/pvcalls: implement connect command
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On 07/31/2017 06:57 PM, Stefano Stabellini wrote:
> Send PVCALLS_CONNECT to the backend. Allocate a new ring and evtchn for
> the active socket.
>
> Introduce fields in struct sock_mapping to keep track of active sockets.
> Introduce a waitqueue to allow the frontend to wait on data coming from
> the backend on the active socket (recvmsg command).
>
> Two mutexes (one of reads and one for writes) will be used to protect
> the active socket in and out rings from concurrent accesses.
>
> Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> CC: boris.ostrovsky@oracle.com
> CC: jgross@suse.com
> ---
> drivers/xen/pvcalls-front.c | 146 ++++++++++++++++++++++++++++++++++++++++++++
> drivers/xen/pvcalls-front.h | 2 +
> 2 files changed, 148 insertions(+)
>
> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> index 7c4a7cb..379b8fb 100644
> --- a/drivers/xen/pvcalls-front.c
> +++ b/drivers/xen/pvcalls-front.c
> @@ -13,6 +13,10 @@
> */
>
> #include <linux/module.h>
> +#include <linux/net.h>
> +#include <linux/socket.h>
> +
> +#include <net/sock.h>
>
> #include <xen/events.h>
> #include <xen/grant_table.h>
> @@ -44,6 +48,18 @@ struct sock_mapping {
> bool active_socket;
> struct list_head list;
> struct socket *sock;
> + union {
> + struct {
> + int irq;
> + grant_ref_t ref;
> + struct pvcalls_data_intf *ring;
> + struct pvcalls_data data;
> + struct mutex in_mutex;
> + struct mutex out_mutex;
> +
> + wait_queue_head_t inflight_conn_req;
> + } active;
> + };
> };
>
> static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
> @@ -97,6 +113,18 @@ static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
> return IRQ_HANDLED;
> }
>
> +static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
> +{
> + struct sock_mapping *map = sock_map;
> +
> + if (map == NULL)
> + return IRQ_HANDLED;
> +
> + wake_up_interruptible(&map->active.inflight_conn_req);
> +
> + return IRQ_HANDLED;
> +}
> +
> int pvcalls_front_socket(struct socket *sock)
> {
> struct pvcalls_bedata *bedata;
> @@ -162,6 +190,124 @@ int pvcalls_front_socket(struct socket *sock)
> return ret;
> }
>
> +static int create_active(struct sock_mapping *map, int *evtchn)
> +{
> + void *bytes;
> + int ret = -ENOMEM, irq = -1, i;
> +
> + init_waitqueue_head(&map->active.inflight_conn_req);
> +
> + map->active.ring = (struct pvcalls_data_intf *)
> + __get_free_page(GFP_KERNEL | __GFP_ZERO);
> + if (map->active.ring == NULL)
> + goto out_error;
> + memset(map->active.ring, 0, XEN_PAGE_SIZE);


Not needed (page allocated with __GFP_ZERO)

BTW, are you operating on XEN_PAGE_SIZE of PAGE_SIZE? Because if it's
the former than __get_free_page() may be way more than what you need.
(below too)


> + map->active.ring->ring_order = PVCALLS_RING_ORDER;
> + bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
> + map->active.ring->ring_order);
> + if (bytes == NULL)
> + goto out_error;
> + for (i = 0; i < (1 << map->active.ring->ring_order); i++)

PVCALLS_RING_ORDER


> + map->active.ring->ref[i] = gnttab_grant_foreign_access(
> + pvcalls_front_dev->otherend_id,
> + pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
> +
> + map->active.ref = gnttab_grant_foreign_access(
> + pvcalls_front_dev->otherend_id,
> + pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
> +
> + map->active.data.in = bytes;
> + map->active.data.out = bytes +
> + XEN_FLEX_RING_SIZE(map->active.ring->ring_order);
> +
> + ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
> + if (ret)
> + goto out_error;
> + irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
> + 0, "pvcalls-frontend", map);
> + if (irq < 0) {
> + ret = irq;
> + goto out_error;
> + }
> +
> + map->active.irq = irq;
> + map->active_socket = true;
> + mutex_init(&map->active.in_mutex);
> + mutex_init(&map->active.out_mutex);
> +
> + return 0;
> +
> +out_error:
> + if (irq >= 0)
> + unbind_from_irqhandler(irq, map);
> + else if (*evtchn >= 0)

*evtchn may have been passed in as >=0. You probably want to set to -1
or something in the beginning.

> + xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
> + kfree(map->active.data.in);
> + kfree(map->active.ring);
> + kfree(map);

Probably a matter of personal style but I think it's better to free map
in the caller.

Actually, should it be freed? The caller gets an error if get_request()
or create_active() fail. In the first case map is not freed. Is the
caller going to distinguish EAGAIN from any other error and know that
map does not need to be allocated?

(Also I think you need to unlink the map from socket_mapping list before
freeing it).

-boris

> + return ret;
> +}
> +
> +int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
> + int addr_len, int flags)
> +{
> + struct pvcalls_bedata *bedata;
> + struct sock_mapping *map = NULL;
> + struct xen_pvcalls_request *req;
> + int notify, req_id, ret, evtchn;
> +
> + if (!pvcalls_front_dev)
> + return -ENETUNREACH;
> + if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
> + return -ENOTSUPP;
> +
> + bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> +
> + map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
> + if (!map)
> + return -EINVAL;
> +
> + spin_lock(&bedata->pvcallss_lock);
> + ret = get_request(bedata, &req_id);
> + if (ret < 0) {
> + spin_unlock(&bedata->pvcallss_lock);
> + return ret;
> + }
> + ret = create_active(map, &evtchn);
> + if (ret < 0) {
> + spin_unlock(&bedata->pvcallss_lock);
> + return ret;
> + }
> +
> + req = RING_GET_REQUEST(&bedata->ring, req_id);
> + req->req_id = req_id;
> + req->cmd = PVCALLS_CONNECT;
> + req->u.connect.id = (uint64_t)map;
> + memcpy(req->u.connect.addr, addr, sizeof(*addr));
> + req->u.connect.len = addr_len;
> + req->u.connect.flags = flags;
> + req->u.connect.ref = map->active.ref;
> + req->u.connect.evtchn = evtchn;
> +
> + map->sock = 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);
> +
> + 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);
> + 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 b7dabed..63b0417 100644
> --- a/drivers/xen/pvcalls-front.h
> +++ b/drivers/xen/pvcalls-front.h
> @@ -4,5 +4,7 @@
> #include <linux/net.h>
>
> int pvcalls_front_socket(struct socket *sock);
> +int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
> + int addr_len, int flags);
>
> #endif
>

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