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[PATCH v3 00/13] introduce the Xen PV Calls frontend

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  [PATCH v3 00/13] introduce the Xen PV Calls frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:00 +0200
    [PATCH v3 12/13] xen/pvcalls: implement release command Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:00 +0200
    [PATCH v3 06/13] xen/pvcalls: implement bind command Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:00 +0200
    [PATCH v3 07/13] xen/pvcalls: implement listen command Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:00 +0200
    [PATCH v3 11/13] xen/pvcalls: implement poll command Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:00 +0200
    [PATCH v3 01/13] xen/pvcalls: introduce the pvcalls xenbus frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 03/13] xen/pvcalls: connect to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 09/13] xen/pvcalls: implement sendmsg Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 13/13] xen: introduce a Kconfig option to enable the pvcalls frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 08/13] xen/pvcalls: implement accept command Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 02/13] xen/pvcalls: implement frontend disconnect Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 10/13] xen/pvcalls: implement recvmsg Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 05/13] xen/pvcalls: implement connect command Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
      [PATCH v3 04/13] xen/pvcalls: implement socket command and handle events Stefano Stabellini <sstabellini@kernel.org> - 2017-08-01 01:10 +0200
    Re: [PATCH v3 00/13] introduce the Xen PV Calls frontend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-08-10 17:10 +0200
      Re: [PATCH v3 00/13] introduce the Xen PV Calls frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-08-10 20:20 +0200

#1700458 — [PATCH v3 00/13] introduce the Xen PV Calls frontend

Hi all,

this series introduces the frontend for the newly introduced PV Calls
procotol.

PV Calls is a paravirtualized protocol that allows the implementation of
a set of POSIX functions in a different domain. The PV Calls frontend
sends POSIX function calls to the backend, which implements them and
returns a value to the frontend and acts on the function call.

For more information about PV Calls, please read:

https://xenbits.xen.org/docs/unstable/misc/pvcalls.html

This patch series only implements the frontend driver. It doesn't
attempt to redirect POSIX calls to it. The functions exported in
pvcalls-front.h are meant to be used for that. A separate patch series
will be sent to use them and hook them into the system.



Changes in v3:

In addition to addressing all comments, in this version of the series I
also made one other significant change: I implemented non-blocking
accept, which I didn't realize was missing in the last version of the
series (non-blocking accept is usually called only after a successful
poll, when there are already outstanding connections to accept). To do
that, I also changed the id for sockets sent to the backend from the
value of the struct socket pointer to the value of the struct
sock_mapping pointer. It's all documented in the patch descriptions.
This is the full list of changes:

- use struct sock_mapping* instead of struct socket* as socket id to
  share with the backend
- allocate struct sock_mapping for a socket in pvcalls_front_socket
- in pvcalls_front_accept check if the request is non-blocking and
  return -EAGAIN in that case
- store req_id and struct sock_mapping * of an inflight accept request,
  so that we can resume when it's ready, in case the accept is
  non-blocking
- remove unnecessary parenthesis
- rename RING_ORDER to PVCALLS_RING_ORDER
- make pvcalls_front_dev static
- remove ref local variable from pvcalls_front_probe
- move patch #12 before patch #2
- move dev_set_drvdata before any got error in pvcalls_front_probe
- combine src and dst calculation lines in pvcalls_front_event_handler
- remove unnecessary != 0 in the wait_event and wait_event_interruptible
  tests
- add an in-code comment about sk_send_head
- In v2 I applied some changes to the wrong patch. Move changes to the
  right patches.
- refactor the code to get a req_id into a function
- use wait_event (instead of wait_event_interruptible) to wait for a
  response from the backend because we cannot cope with missing
  responses
- remove the usage of PVCALLS_FRONT_MAX_SPIN from recvmsg
- remove unnecessary !bedata check in pvcalls_front_release 



Changes in v2:
- use xenbus_read_unsigned when possible
- call dev_set_drvdata earlier in pvcalls_front_probe not to dereference
  a NULL pointer in the error path
- set ret appropriately in pvcalls_front_probe
- include pvcalls-front.h in pvcalls-front.c
- call wake_up only once after the consuming loop in pvcalls_front_event_handler
- don't leak "bytes" in case of errors in create_active
- call spin_unlock appropriately in case of errors in create_active
- remove all BUG_ONs
- don't leak newsock->sk in pvcalls_front_accept in case of errors
- rename PVCALLS_FRON_MAX_SPIN to PVCALLS_FRONT_MAX_SPIN
- return bool from pvcalls_front_read_todo
- add a barrier after setting PVCALLS_FLAG_POLL_RET in
  pvcalls_front_event_handler
- remove outdated comment in pvcalls_front_free_map
- clear sock->sk->sk_send_head later in pvcalls_front_release
- make XEN_PVCALLS_FRONTEND tristate
- don't add an empty resume function



Stefano Stabellini (13):
      xen/pvcalls: introduce the pvcalls xenbus frontend
      xen/pvcalls: implement frontend disconnect
      xen/pvcalls: connect to the backend
      xen/pvcalls: implement socket command and handle events
      xen/pvcalls: implement connect command
      xen/pvcalls: implement bind command
      xen/pvcalls: implement listen command
      xen/pvcalls: implement accept command
      xen/pvcalls: implement sendmsg
      xen/pvcalls: implement recvmsg
      xen/pvcalls: implement poll command
      xen/pvcalls: implement release command
      xen: introduce a Kconfig option to enable the pvcalls frontend

 drivers/xen/Kconfig         |    9 +
 drivers/xen/Makefile        |    1 +
 drivers/xen/pvcalls-front.c | 1140 +++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |   28 ++
 4 files changed, 1178 insertions(+)
 create mode 100644 drivers/xen/pvcalls-front.c
 create mode 100644 drivers/xen/pvcalls-front.h

[toc] | [next] | [standalone]

#1700459 — [PATCH v3 12/13] xen/pvcalls: implement release command

Send PVCALLS_RELEASE to the backend and wait for a reply. Take both
in_mutex and out_mutex to avoid concurrent accesses. Then, free the
socket.

For passive sockets, check whether we have already pre-allocated an
active socket for the purpose of being accepted. If so, free that as
well.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 88 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |  1 +
 2 files changed, 89 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 1c975d6..775a6d2 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -192,6 +192,23 @@ static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
 	return IRQ_HANDLED;
 }
 
+static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
+				   struct sock_mapping *map)
+{
+	int i;
+
+	spin_lock(&bedata->pvcallss_lock);
+	if (!list_empty(&map->list))
+		list_del_init(&map->list);
+	spin_unlock(&bedata->pvcallss_lock);
+
+	for (i = 0; i < (1 << map->active.ring->ring_order); i++)
+		gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
+	gnttab_end_foreign_access(map->active.ref, 0, 0);
+	free_page((unsigned long)map->active.ring);
+	unbind_from_irqhandler(map->active.irq, map);
+}
+
 int pvcalls_front_socket(struct socket *sock)
 {
 	struct pvcalls_bedata *bedata;
@@ -853,6 +870,77 @@ unsigned int pvcalls_front_poll(struct file *file, struct socket *sock,
 		return pvcalls_front_poll_passive(file, bedata, map, wait);
 }
 
+int pvcalls_front_release(struct socket *sock)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	int req_id, notify, ret;
+	struct xen_pvcalls_request *req;
+
+	if (!pvcalls_front_dev)
+		return -EIO;
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	if (sock->sk == NULL)
+		return 0;
+
+	map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+	if (map == NULL)
+		return 0;
+
+	spin_lock(&bedata->pvcallss_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->pvcallss_lock);
+		return ret;
+	}
+	WRITE_ONCE(sock->sk->sk_send_head, NULL);
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_RELEASE;
+	req->u.release.id = (uint64_t)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);
+
+	if (map->active_socket) {
+		/* 
+		 * Set in_error and wake up inflight_conn_req to force
+		 * recvmsg waiters to exit.
+		 */
+		map->active.ring->in_error = -EBADF;
+		wake_up_interruptible(&map->active.inflight_conn_req);
+
+		mutex_lock(&map->active.in_mutex);
+		mutex_lock(&map->active.out_mutex);
+		pvcalls_front_free_map(bedata, map);
+		mutex_unlock(&map->active.out_mutex);
+		mutex_unlock(&map->active.in_mutex);
+		kfree(map);
+	} else {
+		spin_lock(&bedata->pvcallss_lock);
+		if (READ_ONCE(map->passive.inflight_req_id) !=
+		    PVCALLS_INVALID_ID) {
+			pvcalls_front_free_map(bedata,
+					       map->passive.accept_map);
+			kfree(map->passive.accept_map);
+		}
+		list_del_init(&map->list);
+		kfree(map);
+		spin_unlock(&bedata->pvcallss_lock);
+	}
+	WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
+
+	return 0;
+}
+
 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 25e05b8..3332978 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -23,5 +23,6 @@ int pvcalls_front_recvmsg(struct socket *sock,
 unsigned int pvcalls_front_poll(struct file *file,
 				struct socket *sock,
 				poll_table *wait);
+int pvcalls_front_release(struct socket *sock);
 
 #endif
-- 
1.9.1

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#1700463 — [PATCH v3 06/13] xen/pvcalls: implement bind command

Send PVCALLS_BIND to the backend. Introduce a new structure, part of
struct sock_mapping, to store information specific to passive sockets.

Introduce a status field to keep track of the status of the passive
socket.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |  3 +++
 2 files changed, 62 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 379b8fb..5ccef34 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -59,6 +59,13 @@ struct sock_mapping {
 
 			wait_queue_head_t inflight_conn_req;
 		} active;
+		struct {
+		/* Socket status */
+#define PVCALLS_STATUS_UNINITALIZED  0
+#define PVCALLS_STATUS_BIND          1
+#define PVCALLS_STATUS_LISTEN        2
+			uint8_t status;
+		} passive;
 	};
 };
 
@@ -308,6 +315,58 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 	return ret;
 }
 
+int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map = NULL;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret;
+
+	if (!pvcalls_front_dev)
+		return -ENOTCONN;
+	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 == NULL)
+		return -EINVAL;
+
+	spin_lock(&bedata->pvcallss_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->pvcallss_lock);
+		return ret;
+	}
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	map->sock = sock;
+	req->cmd = PVCALLS_BIND;
+	req->u.bind.id = (uint64_t) map;
+	memcpy(req->u.bind.addr, addr, sizeof(*addr));
+	req->u.bind.len = addr_len;
+
+	init_waitqueue_head(&map->passive.inflight_accept_req);
+
+	map->active_socket = false;
+
+	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);
+
+	map->passive.status = PVCALLS_STATUS_BIND;
+	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 0;
+}
+
 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 63b0417..8b0a274 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -6,5 +6,8 @@
 int pvcalls_front_socket(struct socket *sock);
 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 			  int addr_len, int flags);
+int pvcalls_front_bind(struct socket *sock,
+		       struct sockaddr *addr,
+		       int addr_len);
 
 #endif
-- 
1.9.1

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#1700467 — [PATCH v3 07/13] xen/pvcalls: implement listen command

Send PVCALLS_LISTEN to the backend.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |  1 +
 2 files changed, 48 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 5ccef34..b2757f5 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -367,6 +367,53 @@ int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 	return 0;
 }
 
+int pvcalls_front_listen(struct socket *sock, int backlog)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret;
+
+	if (!pvcalls_front_dev)
+		return -ENOTCONN;
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+	if (!map)
+		return -ENOTSOCK;
+
+	if (map->passive.status != PVCALLS_STATUS_BIND)
+		return -EOPNOTSUPP;
+
+	spin_lock(&bedata->pvcallss_lock);
+	ret = get_request(bedata, &req_id);
+	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_LISTEN;
+	req->u.listen.id = (uint64_t) map;
+	req->u.listen.backlog = backlog;
+
+	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);
+
+	map->passive.status = PVCALLS_STATUS_LISTEN;
+	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 8b0a274..aa8fe10 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -9,5 +9,6 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 int pvcalls_front_bind(struct socket *sock,
 		       struct sockaddr *addr,
 		       int addr_len);
+int pvcalls_front_listen(struct socket *sock, int backlog);
 
 #endif
-- 
1.9.1

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#1700468 — [PATCH v3 11/13] xen/pvcalls: implement poll command

For active sockets, check the indexes and use the inflight_conn_req
waitqueue to wait.

For passive sockets if an accept is outstanding
(PVCALLS_FLAG_ACCEPT_INFLIGHT), check if it has been answered by looking
at bedata->rsp[req_id]. If so, return POLLIN.  Otherwise use the
inflight_accept_req waitqueue.

If no accepts are inflight, send PVCALLS_POLL to the backend. If we have
outstanding POLL requests awaiting for a response 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 sock_mapping from the
poll id (we previously converted struct sock_mapping* to uint64_t and
used it as id).

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 135 +++++++++++++++++++++++++++++++++++++++++---
 drivers/xen/pvcalls-front.h |   3 +
 2 files changed, 129 insertions(+), 9 deletions(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 635a83a..1c975d6 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -72,6 +72,8 @@ struct sock_mapping {
 		 * Only one poll operation can be inflight for a given socket.
 		 */
 #define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
+#define PVCALLS_FLAG_POLL_INFLIGHT   1
+#define PVCALLS_FLAG_POLL_RET        2
 			uint8_t flags;
 			uint32_t inflight_req_id;
 			struct sock_mapping *accept_map;
@@ -139,15 +141,32 @@ 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;
-		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);
+		if (rsp->cmd == PVCALLS_POLL) {
+			struct sock_mapping *map = (struct sock_mapping *)
+						   rsp->u.poll.id;
+
+			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();
+			clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+				  (void *)&map->passive.flags);
+		} else {
+			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++;
@@ -736,6 +755,104 @@ 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, ret;
+	struct xen_pvcalls_request *req;
+
+	if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+		     (void *)&map->passive.flags)) {
+		uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
+		if (req_id != PVCALLS_INVALID_ID &&
+		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
+			return POLLIN;
+
+		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);
+	ret = get_request(bedata, &req_id);
+	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_POLL;
+	req->u.poll.id = (uint64_t) 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);
+
+	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);
+}
+
 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
-- 
1.9.1

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#1700477 — [PATCH v3 01/13] xen/pvcalls: introduce the pvcalls xenbus frontend

Introduce a xenbus frontend for the pvcalls protocol, as defined by
https://xenbits.xen.org/docs/unstable/misc/pvcalls.html.

This patch only adds the stubs, the code will be added by the following
patches.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 61 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 drivers/xen/pvcalls-front.c

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
new file mode 100644
index 0000000..a8d38c2
--- /dev/null
+++ b/drivers/xen/pvcalls-front.c
@@ -0,0 +1,61 @@
+/*
+ * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/pvcalls.h>
+
+static const struct xenbus_device_id pvcalls_front_ids[] = {
+	{ "pvcalls" },
+	{ "" }
+};
+
+static int pvcalls_front_remove(struct xenbus_device *dev)
+{
+	return 0;
+}
+
+static int pvcalls_front_probe(struct xenbus_device *dev,
+			  const struct xenbus_device_id *id)
+{
+	return 0;
+}
+
+static void pvcalls_front_changed(struct xenbus_device *dev,
+			    enum xenbus_state backend_state)
+{
+}
+
+static struct xenbus_driver pvcalls_front_driver = {
+	.ids = pvcalls_front_ids,
+	.probe = pvcalls_front_probe,
+	.remove = pvcalls_front_remove,
+	.otherend_changed = pvcalls_front_changed,
+};
+
+static int __init pvcalls_frontend_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	pr_info("Initialising Xen pvcalls frontend driver\n");
+
+	return xenbus_register_frontend(&pvcalls_front_driver);
+}
+
+module_init(pvcalls_frontend_init);
-- 
1.9.1

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#1700478 — [PATCH v3 03/13] xen/pvcalls: connect to the backend

Implement the probe function for the pvcalls frontend. Read the
supported versions, max-page-order and function-calls nodes from
xenstore.

Only one frontend<->backend connection is supported at any given time
for a guest. Store the active frontend device to a static pointer.

Introduce a stub functions for the event handler.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 130 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index a126195..2afe36d 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -84,12 +84,142 @@ static int pvcalls_front_remove(struct xenbus_device *dev)
 static int pvcalls_front_probe(struct xenbus_device *dev,
 			  const struct xenbus_device_id *id)
 {
+	int ret = -ENOMEM, evtchn, i;
+	unsigned int max_page_order, function_calls, len;
+	char *versions;
+	grant_ref_t gref_head = 0;
+	struct xenbus_transaction xbt;
+	struct pvcalls_bedata *bedata = NULL;
+	struct xen_pvcalls_sring *sring;
+
+	if (pvcalls_front_dev != NULL) {
+		dev_err(&dev->dev, "only one PV Calls connection supported\n");
+		return -EINVAL;
+	}
+
+	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
+	if (!len)
+		return -EINVAL;
+	if (strcmp(versions, "1")) {
+		kfree(versions);
+		return -EINVAL;
+	}
+	kfree(versions);
+	max_page_order = xenbus_read_unsigned(dev->otherend,
+					      "max-page-order", 0);
+	if (max_page_order < PVCALLS_RING_ORDER)
+		return -ENODEV;
+	function_calls = xenbus_read_unsigned(dev->otherend,
+					      "function-calls", 0);
+	if (function_calls != 1)
+		return -ENODEV;
+	pr_info("%s max-page-order is %u\n", __func__, max_page_order);
+
+	bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
+	if (!bedata)
+		return -ENOMEM;
+
+	dev_set_drvdata(&dev->dev, bedata);
+	pvcalls_front_dev = dev;
+	init_waitqueue_head(&bedata->inflight_req);
+	for (i = 0; i < PVCALLS_NR_REQ_PER_RING; i++)
+		bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
+
+	sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
+							     __GFP_ZERO);
+	if (!sring)
+		goto error;
+	SHARED_RING_INIT(sring);
+	FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
+
+	ret = xenbus_alloc_evtchn(dev, &evtchn);
+	if (ret)
+		goto error;
+
+	bedata->irq = bind_evtchn_to_irqhandler(evtchn,
+						pvcalls_front_event_handler,
+						0, "pvcalls-frontend", dev);
+	if (bedata->irq < 0) {
+		ret = bedata->irq;
+		goto error;
+	}
+
+	ret = gnttab_alloc_grant_references(1, &gref_head);
+	if (ret < 0)
+		goto error;
+	bedata->ref = gnttab_claim_grant_reference(&gref_head);
+	if (bedata->ref < 0) {
+		ret = bedata->ref;
+		goto error;
+	}
+	gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
+					virt_to_gfn((void *)sring), 0);
+
+ again:
+	ret = xenbus_transaction_start(&xbt);
+	if (ret) {
+		xenbus_dev_fatal(dev, ret, "starting transaction");
+		goto error;
+	}
+	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
+			    evtchn);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_transaction_end(xbt, 0);
+	if (ret) {
+		if (ret == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, ret, "completing transaction");
+		goto error;
+	}
+
+	INIT_LIST_HEAD(&bedata->socket_mappings);
+	INIT_LIST_HEAD(&bedata->socketpass_mappings);
+	spin_lock_init(&bedata->pvcallss_lock);
+	xenbus_switch_state(dev, XenbusStateInitialised);
+
 	return 0;
+
+ error_xenbus:
+	xenbus_transaction_end(xbt, 1);
+	xenbus_dev_fatal(dev, ret, "writing xenstore");
+ error:
+	pvcalls_front_remove(dev);
+	return ret;
 }
 
 static void pvcalls_front_changed(struct xenbus_device *dev,
 			    enum xenbus_state backend_state)
 {
+	switch (backend_state) {
+	case XenbusStateReconfiguring:
+	case XenbusStateReconfigured:
+	case XenbusStateInitialising:
+	case XenbusStateInitialised:
+	case XenbusStateUnknown:
+		break;
+
+	case XenbusStateInitWait:
+		break;
+
+	case XenbusStateConnected:
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's CLOSING state -- fallthrough */
+	case XenbusStateClosing:
+		xenbus_frontend_closed(dev);
+		break;
+	}
 }
 
 static struct xenbus_driver pvcalls_front_driver = {
-- 
1.9.1

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#1700480 — [PATCH v3 09/13] xen/pvcalls: implement sendmsg

Send data to an active socket by copying data to the "out" ring. Take
the active socket out_mutex so that only one function can access the
ring at any given time.

If not enough room is available on the ring, rather than returning
immediately or sleep-waiting, spin for up to 5000 cycles. This small
optimization turns out to improve performance significantly.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 109 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |   3 ++
 2 files changed, 112 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index f83b910..369acde 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -29,6 +29,7 @@
 #define PVCALLS_INVALID_ID UINT_MAX
 #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
 #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
+#define PVCALLS_FRONT_MAX_SPIN 5000
 
 struct pvcalls_bedata {
 	struct xen_pvcalls_front_ring ring;
@@ -88,6 +89,22 @@ static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
 	return 0;
 }
 
+static int pvcalls_front_write_todo(struct sock_mapping *map)
+{
+	struct pvcalls_data_intf *intf = map->active.ring;
+	RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(intf->ring_order);
+	int32_t error;
+
+	cons = intf->out_cons;
+	prod = intf->out_prod;
+	error = intf->out_error;
+	if (error == -ENOTCONN)
+		return 0;
+	if (error != 0)
+		return error;
+	return size - pvcalls_queued(prod, cons, size);
+}
+
 static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 {
 	struct xenbus_device *dev = dev_id;
@@ -325,6 +342,98 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 	return ret;
 }
 
+static int __write_ring(struct pvcalls_data_intf *intf,
+			struct pvcalls_data *data,
+			struct iov_iter *msg_iter,
+			size_t len)
+{
+	RING_IDX cons, prod, size, masked_prod, masked_cons;
+	RING_IDX array_size = XEN_FLEX_RING_SIZE(intf->ring_order);
+	int32_t error;
+
+	cons = intf->out_cons;
+	prod = intf->out_prod;
+	error = intf->out_error;
+	/* read indexes before continuing */
+	virt_mb();
+
+	if (error < 0)
+		return error;
+
+	size = pvcalls_queued(prod, cons, array_size);
+	if (size >= array_size)
+		return 0;
+	if (len > array_size - size)
+		len = array_size - size;
+
+	masked_prod = pvcalls_mask(prod, array_size);
+	masked_cons = pvcalls_mask(cons, array_size);
+
+	if (masked_prod < masked_cons) {
+		copy_from_iter(data->out + masked_prod, len, msg_iter);
+	} else {
+		if (len > array_size - masked_prod) {
+			copy_from_iter(data->out + masked_prod,
+				       array_size - masked_prod, msg_iter);
+			copy_from_iter(data->out,
+				       len - (array_size - masked_prod),
+				       msg_iter);
+		} else {
+			copy_from_iter(data->out + masked_prod, len, msg_iter);
+		}
+	}
+	/* write to ring before updating pointer */
+	virt_wmb();
+	intf->out_prod += len;
+
+	return len;
+}
+
+int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
+			  size_t len)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	int sent = 0, tot_sent = 0;
+	int count = 0, flags;
+
+	if (!pvcalls_front_dev)
+		return -ENOTCONN;
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+	if (!map)
+		return -ENOTSOCK;
+
+	flags = msg->msg_flags;
+	if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
+		return -EOPNOTSUPP;
+
+	mutex_lock(&map->active.out_mutex);
+	if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
+		mutex_unlock(&map->active.out_mutex);
+		return -EAGAIN;
+	}
+
+again:
+	count++;
+	sent = __write_ring(map->active.ring,
+			    &map->active.data, &msg->msg_iter,
+			    len);
+	if (sent > 0) {
+		len -= sent;
+		tot_sent += sent;
+		notify_remote_via_irq(map->active.irq);
+	}
+	if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
+		goto again;
+	if (sent < 0)
+		tot_sent = sent;
+
+	mutex_unlock(&map->active.out_mutex);
+	return tot_sent;
+}
+
 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 {
 	struct pvcalls_bedata *bedata;
diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
index ab4f1da..d937c24 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -13,5 +13,8 @@ int pvcalls_front_bind(struct socket *sock,
 int pvcalls_front_accept(struct socket *sock,
 			 struct socket *newsock,
 			 int flags);
+int pvcalls_front_sendmsg(struct socket *sock,
+			  struct msghdr *msg,
+			  size_t len);
 
 #endif
-- 
1.9.1

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#1700482 — [PATCH v3 13/13] xen: introduce a Kconfig option to enable the pvcalls frontend

Also add pvcalls-front to the Makefile.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/Kconfig  | 9 +++++++++
 drivers/xen/Makefile | 1 +
 2 files changed, 10 insertions(+)

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 4545561..0b2c828 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -196,6 +196,15 @@ config XEN_PCIDEV_BACKEND
 
 	  If in doubt, say m.
 
+config XEN_PVCALLS_FRONTEND
+	tristate "XEN PV Calls frontend driver"
+	depends on INET && XEN
+	help
+	  Experimental frontend for the Xen PV Calls protocol
+	  (https://xenbits.xen.org/docs/unstable/misc/pvcalls.html). It
+	  sends a small set of POSIX calls to the backend, which
+	  implements them.
+
 config XEN_PVCALLS_BACKEND
 	bool "XEN PV Calls backend driver"
 	depends on INET && XEN && XEN_BACKEND
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 480b928..afb9e03 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_XEN_EFI)			+= efi.o
 obj-$(CONFIG_XEN_SCSI_BACKEND)		+= xen-scsiback.o
 obj-$(CONFIG_XEN_AUTO_XLATE)		+= xlate_mmu.o
 obj-$(CONFIG_XEN_PVCALLS_BACKEND)	+= pvcalls-back.o
+obj-$(CONFIG_XEN_PVCALLS_FRONTEND)	+= pvcalls-front.o
 xen-evtchn-y				:= evtchn.o
 xen-gntdev-y				:= gntdev.o
 xen-gntalloc-y				:= gntalloc.o
-- 
1.9.1

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#1700487 — [PATCH v3 08/13] xen/pvcalls: implement accept command

Introduce a waitqueue to allow only one outstanding accept command at
any given time and to implement polling on the passive socket. Introduce
a flags field to keep track of in-flight accept and poll commands.

Send PVCALLS_ACCEPT to the backend. Allocate a new active socket. Make
sure that only one accept command is executed at any given time by
setting PVCALLS_FLAG_ACCEPT_INFLIGHT and waiting on the
inflight_accept_req waitqueue.

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

Check if the accept call is non-blocking: in that case after sending the
ACCEPT command to the backend store the sock_mapping pointer of the new
struct and the inflight req_id then return -EAGAIN (which will respond
only when there is something to accept). Next time accept is called,
we'll check if the ACCEPT command has been answered, if so we'll pick up
where we left off, otherwise we return -EAGAIN again.

Note that, differently from the other commands, we can use
wait_event_interruptible (instead of wait_event) in the case of accept
as we are able to track the req_id of the ACCEPT response that we are
waiting.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 111 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |   3 ++
 2 files changed, 114 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index b2757f5..f83b910 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -65,6 +65,16 @@ struct sock_mapping {
 #define PVCALLS_STATUS_BIND          1
 #define PVCALLS_STATUS_LISTEN        2
 			uint8_t status;
+		/*
+		 * Internal state-machine flags.
+		 * Only one accept operation can be inflight for a socket.
+		 * Only one poll operation can be inflight for a given socket.
+		 */
+#define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
+			uint8_t flags;
+			uint32_t inflight_req_id;
+			struct sock_mapping *accept_map;
+			wait_queue_head_t inflight_accept_req;
 		} passive;
 	};
 };
@@ -414,6 +424,107 @@ int pvcalls_front_listen(struct socket *sock, int backlog)
 	return ret;
 }
 
+int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
+{
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map;
+	struct sock_mapping *map2 = NULL;
+	struct xen_pvcalls_request *req;
+	int notify, req_id, ret, evtchn, nonblock;
+
+	if (!pvcalls_front_dev)
+		return -ENOTCONN;
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+	if (!map)
+		return -ENOTSOCK;
+
+	if (map->passive.status != PVCALLS_STATUS_LISTEN)
+		return -EINVAL;
+
+	nonblock = flags & SOCK_NONBLOCK;
+	/*
+	 * Backend only supports 1 inflight accept request, will return
+	 * errors for the others
+	 */
+	if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+			     (void *)&map->passive.flags)) {
+		req_id = READ_ONCE(map->passive.inflight_req_id);
+		if (req_id != PVCALLS_INVALID_ID &&
+		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
+			goto received;
+		if (nonblock)
+			return -EAGAIN;
+		if (wait_event_interruptible(map->passive.inflight_accept_req,
+			!test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+					  (void *)&map->passive.flags)))
+			return -EINTR;
+	}
+
+	spin_lock(&bedata->pvcallss_lock);
+	ret = get_request(bedata, &req_id);
+	if (ret < 0) {
+		spin_unlock(&bedata->pvcallss_lock);
+		return ret;
+	}	
+	map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
+	if (map2 == NULL)
+	    return -ENOMEM;
+	ret =  create_active(map2, &evtchn);
+	if (ret < 0) {
+	    kfree(map2);
+	    return -ENOMEM;
+	}
+	list_add_tail(&map2->list, &bedata->socket_mappings);
+
+	req = RING_GET_REQUEST(&bedata->ring, req_id);
+	req->req_id = req_id;
+	req->cmd = PVCALLS_ACCEPT;
+	req->u.accept.id = (uint64_t) map;
+	req->u.accept.ref = map2->active.ref;
+	req->u.accept.id_new = (uint64_t) map2;
+	req->u.accept.evtchn = evtchn;
+	map->passive.accept_map = map2;
+
+	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);
+	if (nonblock) {
+		WRITE_ONCE(map->passive.inflight_req_id, req_id);
+		return -EAGAIN;
+	}
+
+	if (wait_event_interruptible(bedata->inflight_req,
+		READ_ONCE(bedata->rsp[req_id].req_id) == req_id))
+	    return -EINTR;
+
+received:
+	map2 = map->passive.accept_map;
+	map2->sock = newsock;
+	newsock->sk = kzalloc(sizeof(*newsock->sk), GFP_KERNEL);
+	if (!newsock->sk) {
+	    WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
+	    WRITE_ONCE(map->passive.inflight_req_id, PVCALLS_INVALID_ID);
+	    pvcalls_front_free_map(bedata, map2);
+	    kfree(map2);
+	    return -ENOMEM;
+	}
+	WRITE_ONCE(newsock->sk->sk_send_head, (void *)map2);
+
+	clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
+	wake_up(&map->passive.inflight_accept_req);
+
+	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);
+	WRITE_ONCE(map->passive.inflight_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 aa8fe10..ab4f1da 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -10,5 +10,8 @@ int pvcalls_front_bind(struct socket *sock,
 		       struct sockaddr *addr,
 		       int addr_len);
 int pvcalls_front_listen(struct socket *sock, int backlog);
+int pvcalls_front_accept(struct socket *sock,
+			 struct socket *newsock,
+			 int flags);
 
 #endif
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1700488 — [PATCH v3 02/13] xen/pvcalls: implement frontend disconnect

Introduce a data structure named pvcalls_bedata. It contains pointers to
the command ring, the event channel, a list of active sockets and a list
of passive sockets. Lists accesses are protected by a spin_lock.

Introduce a waitqueue to allow waiting for a response on commands sent
to the backend.

Introduce an array of struct xen_pvcalls_response to store commands
responses.

Implement pvcalls frontend removal function. Go through the list of
active and passive sockets and free them all, one at a time.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index a8d38c2..a126195 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -20,6 +20,29 @@
 #include <xen/xenbus.h>
 #include <xen/interface/io/pvcalls.h>
 
+#define PVCALLS_INVALID_ID UINT_MAX
+#define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
+#define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
+
+struct pvcalls_bedata {
+	struct xen_pvcalls_front_ring ring;
+	grant_ref_t ref;
+	int irq;
+
+	struct list_head socket_mappings;
+	struct list_head socketpass_mappings;
+	spinlock_t pvcallss_lock;
+
+	wait_queue_head_t inflight_req;
+	struct xen_pvcalls_response rsp[PVCALLS_NR_REQ_PER_RING];
+};
+static struct xenbus_device *pvcalls_front_dev;
+
+static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
+{
+	return IRQ_HANDLED;
+}
+
 static const struct xenbus_device_id pvcalls_front_ids[] = {
 	{ "pvcalls" },
 	{ "" }
@@ -27,6 +50,34 @@
 
 static int pvcalls_front_remove(struct xenbus_device *dev)
 {
+	struct pvcalls_bedata *bedata;
+	struct sock_mapping *map = NULL, *n;
+
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
+		mutex_lock(&map->active.in_mutex);
+		mutex_lock(&map->active.out_mutex);
+		pvcalls_front_free_map(bedata, map);
+		mutex_unlock(&map->active.out_mutex);
+		mutex_unlock(&map->active.in_mutex);
+		kfree(map);
+	}
+	list_for_each_entry_safe(map, n, &bedata->socketpass_mappings, list) {
+		spin_lock(&bedata->pvcallss_lock);
+		list_del_init(&map->list);
+		spin_unlock(&bedata->pvcallss_lock);
+		kfree(map);
+	}
+	if (bedata->irq > 0)
+		unbind_from_irqhandler(bedata->irq, dev);
+	if (bedata->ref >= 0)
+		gnttab_end_foreign_access(bedata->ref, 0, 0);
+	kfree(bedata->ring.sring);
+	kfree(bedata);
+	dev_set_drvdata(&dev->dev, NULL);
+	xenbus_switch_state(dev, XenbusStateClosed);
+	pvcalls_front_dev = NULL;
 	return 0;
 }
 
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1700491 — [PATCH v3 10/13] xen/pvcalls: implement recvmsg

Implement recvmsg by copying data from the "in" ring. If not enough data
is available and the recvmsg call is blocking, then wait on the
inflight_conn_req waitqueue. Take the active socket in_mutex so that
only one function can access the ring at any given time.

If no data is available on the ring, rather than returning immediately
or sleep-waiting, spin for up to 5000 cycles. This small optimization
turns out to improve performance and latency significantly.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 102 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |   4 ++
 2 files changed, 106 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 369acde..635a83a 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -105,6 +105,20 @@ static int pvcalls_front_write_todo(struct sock_mapping *map)
 	return size - pvcalls_queued(prod, cons, size);
 }
 
+static bool pvcalls_front_read_todo(struct sock_mapping *map)
+{
+	struct pvcalls_data_intf *intf = map->active.ring;
+	RING_IDX cons, prod;
+	int32_t error;
+
+	cons = intf->in_cons;
+	prod = intf->in_prod;
+	error = intf->in_error;
+	return (error != 0 ||
+		pvcalls_queued(prod, cons,
+			       XEN_FLEX_RING_SIZE(intf->ring_order)) != 0);
+}
+
 static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 {
 	struct xenbus_device *dev = dev_id;
@@ -434,6 +448,94 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 	return tot_sent;
 }
 
+static int __read_ring(struct pvcalls_data_intf *intf,
+		       struct pvcalls_data *data,
+		       struct iov_iter *msg_iter,
+		       size_t len, int flags)
+{
+	RING_IDX cons, prod, size, masked_prod, masked_cons;
+	RING_IDX array_size = XEN_FLEX_RING_SIZE(intf->ring_order);
+	int32_t error;
+
+	cons = intf->in_cons;
+	prod = intf->in_prod;
+	error = intf->in_error;
+	/* get pointers before reading from the ring */
+	virt_rmb();
+	if (error < 0)
+		return error;
+
+	size = pvcalls_queued(prod, cons, array_size);
+	masked_prod = pvcalls_mask(prod, array_size);
+	masked_cons = pvcalls_mask(cons, array_size);
+
+	if (size == 0)
+		return 0;
+
+	if (len > size)
+		len = size;
+
+	if (masked_prod > masked_cons) {
+		copy_to_iter(data->in + masked_cons, len, msg_iter);
+	} else {
+		if (len > (array_size - masked_cons)) {
+			copy_to_iter(data->in + masked_cons,
+				     array_size - masked_cons, msg_iter);
+			copy_to_iter(data->in,
+				     len - (array_size - masked_cons),
+				     msg_iter);
+		} else {
+			copy_to_iter(data->in + masked_cons, len, msg_iter);
+		}
+	}
+	/* read data from the ring before increasing the index */
+	virt_mb();
+	if (!(flags & MSG_PEEK))
+		intf->in_cons += len;
+
+	return len;
+}
+
+int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+		     int flags)
+{
+	struct pvcalls_bedata *bedata;
+	int ret = -EAGAIN;
+	struct sock_mapping *map;
+
+	if (!pvcalls_front_dev)
+		return -ENOTCONN;
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+	if (!map)
+		return -ENOTSOCK;
+
+	if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
+		return -EOPNOTSUPP;
+
+	mutex_lock(&map->active.in_mutex);
+	if (len > XEN_FLEX_RING_SIZE(map->active.ring->ring_order))
+		len = XEN_FLEX_RING_SIZE(map->active.ring->ring_order);
+
+	while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
+		wait_event_interruptible(map->active.inflight_conn_req,
+					 pvcalls_front_read_todo(map));
+	}
+	ret = __read_ring(map->active.ring, &map->active.data,
+			  &msg->msg_iter, len, flags);
+
+	if (ret > 0)
+		notify_remote_via_irq(map->active.irq);
+	if (ret == 0)
+		ret = -EAGAIN;
+	if (ret == -ENOTCONN)
+		ret = 0;
+
+	mutex_unlock(&map->active.in_mutex);
+	return ret;
+}
+
 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 {
 	struct pvcalls_bedata *bedata;
diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
index d937c24..de24041 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -16,5 +16,9 @@ int pvcalls_front_accept(struct socket *sock,
 int pvcalls_front_sendmsg(struct socket *sock,
 			  struct msghdr *msg,
 			  size_t len);
+int pvcalls_front_recvmsg(struct socket *sock,
+			  struct msghdr *msg,
+			  size_t len,
+			  int flags);
 
 #endif
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1700493 — [PATCH v3 05/13] xen/pvcalls: implement connect command

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);
+	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++)
+		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)
+		xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
+	kfree(map->active.data.in);
+	kfree(map->active.ring);
+	kfree(map);
+	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
-- 
1.9.1

[toc] | [prev] | [next] | [standalone]

#1700495 — [PATCH v3 04/13] xen/pvcalls: implement socket command and handle events

Send a PVCALLS_SOCKET command to the backend, use the masked
req_prod_pvt as req_id. This way, req_id is guaranteed to be between 0
and PVCALLS_NR_REQ_PER_RING. We already have a slot in the rsp array
ready for the response, and there cannot be two outstanding responses
with the same req_id.

Wait for the response by waiting on the inflight_req waitqueue and
check for the req_id field in rsp[req_id]. Use atomic accesses and
barriers to read the field. Note that the barriers are simple smp
barriers (as opposed to virt barriers) because they are for internal
frontend synchronization, not frontend<->backend communication.

Once a response is received, clear the corresponding rsp slot by setting
req_id to PVCALLS_INVALID_ID. Note that PVCALLS_INVALID_ID is invalid
only from the frontend point of view. It is not part of the PVCalls
protocol.

pvcalls_front_event_handler is in charge of copying responses from the
ring to the appropriate rsp slot. It is done by copying the body of the
response first, then by copying req_id atomically. After the copies,
wake up anybody waiting on waitqueue.

pvcallss_lock protects accesses to the ring.

Create a new struct sock_mapping and convert the pointer into an
uint64_t and use it as id for the new socket to pass to the backend. The
struct will be fully initialized later on connect or bind. In this patch
the struct sock_mapping is empty, the fields will be added by the next
patch.

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.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
 drivers/xen/pvcalls-front.c | 119 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |   8 +++
 2 files changed, 127 insertions(+)
 create mode 100644 drivers/xen/pvcalls-front.h

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 2afe36d..7c4a7cb 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -20,6 +20,8 @@
 #include <xen/xenbus.h>
 #include <xen/interface/io/pvcalls.h>
 
+#include "pvcalls-front.h"
+
 #define PVCALLS_INVALID_ID UINT_MAX
 #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
 #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
@@ -38,11 +40,128 @@ struct pvcalls_bedata {
 };
 static struct xenbus_device *pvcalls_front_dev;
 
+struct sock_mapping {
+	bool active_socket;
+	struct list_head list;
+	struct socket *sock;
+};
+
+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;
+
+	bedata = dev_get_drvdata(&dev->dev);
+	if (bedata == NULL)
+		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);
 	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;
+
+	if (!pvcalls_front_dev)
+		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)
+	    return -ENOTSUPP;
+
+	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+	map = kzalloc(sizeof(*map), GFP_KERNEL);
+	if (map == NULL)
+		return -ENOMEM;
+	/*
+	 * 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.
+	 */
+	WRITE_ONCE(sock->sk->sk_send_head, (void *)map);
+
+	spin_lock(&bedata->pvcallss_lock);
+	list_add_tail(&map->list, &bedata->socket_mappings);
+
+	ret = get_request(bedata, &req_id);
+	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_SOCKET;
+	req->u.socket.id = (uint64_t) map;
+	req->u.socket.domain = AF_INET;
+	req->u.socket.type = SOCK_STREAM;
+	req->u.socket.protocol = 0;
+
+	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
new file mode 100644
index 0000000..b7dabed
--- /dev/null
+++ b/drivers/xen/pvcalls-front.h
@@ -0,0 +1,8 @@
+#ifndef __PVCALLS_FRONT_H__
+#define __PVCALLS_FRONT_H__
+
+#include <linux/net.h>
+
+int pvcalls_front_socket(struct socket *sock);
+
+#endif
-- 
1.9.1

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#1708714

On 07/31/2017 06:57 PM, Stefano Stabellini wrote:
> Hi all,
>
> this series introduces the frontend for the newly introduced PV Calls
> procotol.
>
> PV Calls is a paravirtualized protocol that allows the implementation of
> a set of POSIX functions in a different domain. The PV Calls frontend
> sends POSIX function calls to the backend, which implements them and
> returns a value to the frontend and acts on the function call.
>
> For more information about PV Calls, please read:
>
> https://xenbits.xen.org/docs/unstable/misc/pvcalls.html
>
> This patch series only implements the frontend driver. It doesn't
> attempt to redirect POSIX calls to it. The functions exported in
> pvcalls-front.h are meant to be used for that. A separate patch series
> will be sent to use them and hook them into the system.

Stefano,


Should this be reviewed or are you going to send another version?

-boris

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#1708952

On Thu, 10 Aug 2017, Boris Ostrovsky wrote:
> On 07/31/2017 06:57 PM, Stefano Stabellini wrote:
> > Hi all,
> >
> > this series introduces the frontend for the newly introduced PV Calls
> > procotol.
> >
> > PV Calls is a paravirtualized protocol that allows the implementation of
> > a set of POSIX functions in a different domain. The PV Calls frontend
> > sends POSIX function calls to the backend, which implements them and
> > returns a value to the frontend and acts on the function call.
> >
> > For more information about PV Calls, please read:
> >
> > https://xenbits.xen.org/docs/unstable/misc/pvcalls.html
> >
> > This patch series only implements the frontend driver. It doesn't
> > attempt to redirect POSIX calls to it. The functions exported in
> > pvcalls-front.h are meant to be used for that. A separate patch series
> > will be sent to use them and hook them into the system.
> 
> Stefano,
> 
> 
> Should this be reviewed or are you going to send another version?

Sorry for the delay, I am dealing with a personal issue at the moment
and I didn't manage to address your valid comments on the release
function implementation.

However in this version I did address all other comments, so it would be
good if you could give a look at it, bearing in mind that the problem on
release is still unaddressed here.

Thanks,

Stefano

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