[PATCH v1 04/13] xen/pvcalls: implement connect command

[Stefano Stabellini]

Send PVCALLS_CONNECT to the backend. Allocate a new ring and evtchn for
the active socket.

Introduce a data structure to keep track of 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.

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.

Convert the struct socket pointer into an uint64_t and use it as id for
the new socket to pass to the backend.

Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
CC: boris.ostrovsky@xxxxxxxxxx
CC: jgross@xxxxxxxx
---
 drivers/xen/pvcalls-front.c | 153 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |   2 +
 2 files changed, 155 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 7933c73..0d305e0 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -13,6 +13,8 @@
  */
 
 #include <linux/module.h>
+#include <linux/net.h>
+#include <linux/socket.h>
 
 #include <xen/events.h>
 #include <xen/grant_table.h>
@@ -20,6 +22,8 @@
 #include <xen/xenbus.h>
 #include <xen/interface/io/pvcalls.h>
 
+#include <net/sock.h>
+
 #define PVCALLS_INVALID_ID (UINT_MAX)
 #define RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
 #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
@@ -38,6 +42,24 @@ struct pvcalls_bedata {
 };
 struct xenbus_device *pvcalls_front_dev;
 
+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 irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 {
 	struct xenbus_device *dev = dev_id;
@@ -80,6 +102,18 @@ 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;
@@ -134,6 +168,125 @@ int pvcalls_front_socket(struct socket *sock)
 	return ret;
 }
 
+static struct sock_mapping *create_active(int *evtchn)
+{
+	struct sock_mapping *map = NULL;
+	void *bytes;
+	int ret, irq = -1, i;
+
+	map = kzalloc(sizeof(*map), GFP_KERNEL);
+	if (map == NULL)
+		return NULL;
+
+	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);
+	map->active.ring->ring_order = 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++)
+		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);
+
+	ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
+	if (ret)
+		goto out_error;
+	map->active.data.in = bytes;
+	map->active.data.out = bytes +
+		XEN_FLEX_RING_SIZE(map->active.ring->ring_order);
+	irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
+					0, "pvcalls-frontend", map);
+	if (irq < 0)
+		goto out_error;
+
+	map->active.irq = irq;
+	map->active_socket = true;
+	mutex_init(&map->active.in_mutex);
+	mutex_init(&map->active.out_mutex);
+
+	return map;
+
+out_error:
+	if (irq >= 0)
+		unbind_from_irqhandler(irq, map);
+	else if (*evtchn >= 0)
+		xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
+	kfree(map->active.data.in);
+	kfree(map->active.ring);
+	kfree(map);
+	return NULL;
+}
+
+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);
+
+	spin_lock(&bedata->pvcallss_lock);
+	req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
+	BUG_ON(req_id >= PVCALLS_NR_REQ_PER_RING);
+	if (RING_FULL(&bedata->ring) ||
+	    READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
+		spin_unlock(&bedata->pvcallss_lock);
+		return -EAGAIN;
+	}
+
+	map = create_active(&evtchn);
+	if (!map)
+	    return -ENOMEM;
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_CONNECT;
+	req->u.connect.id = (uint64_t)sock;
+	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;
+	
+	list_add_tail(&map->list, &bedata->socket_mappings);
+	map->sock = sock;
+	WRITE_ONCE(sock->sk->sk_send_head, (void *)map);
+
+	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
-- 
1.9.1