Re: [PATCH v2 04/13] xen/pvcalls: implement connect command

[Stefano Stabellini]

On Wed, 26 Jul 2017, Boris Ostrovsky wrote:
> On 7/25/2017 5:22 PM, Stefano Stabellini wrote:
> > 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.
> 
> This needs to be documented in the code, not (just) in commit message.

I'll add an in-code comment


> > 
> > 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 | 177
> > +++++++++++++++++++++++++++++++++++++++++---
> >   drivers/xen/pvcalls-front.h |   2 +
> >   2 files changed, 168 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index d1dbcf1..d0f5f42 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>
> > @@ -40,6 +44,24 @@ 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;
> > @@ -84,6 +106,18 @@ 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;
> > @@ -137,6 +171,127 @@ 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);
> > +
> > +	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)
> > +		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);
> > +	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) {
> > +		spin_unlock(&bedata->pvcallss_lock);
> > +		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" },
> >   	{ "" }
> > @@ -150,7 +305,7 @@ 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 = -EFAULT, evtchn, ref = -1, i;
> > +	int ret = -ENOMEM, evtchn, ref = -1, i;
> >   	unsigned int max_page_order, function_calls, len;
> >   	char *versions;
> >   	grant_ref_t gref_head = 0;
> > @@ -171,15 +326,13 @@ static int pvcalls_front_probe(struct xenbus_device
> > *dev,
> >   		return -EINVAL;
> >   	}
> >   	kfree(versions);
> > -	ret = xenbus_scanf(XBT_NIL, dev->otherend,
> > -			   "max-page-order", "%u", &max_page_order);
> > -	if (ret <= 0)
> > -		return -ENODEV;
> > +	max_page_order = xenbus_read_unsigned(dev->otherend,
> > +			   "max-page-order", 0);
> >   	if (max_page_order < RING_ORDER)
> >   		return -ENODEV;
> > -	ret = xenbus_scanf(XBT_NIL, dev->otherend,
> > -			   "function-calls", "%u", &function_calls);
> > -	if (ret <= 0 || function_calls != 1)
> > +	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);
> >   @@ -187,6 +340,8 @@ static int pvcalls_front_probe(struct xenbus_device
> > *dev,
> >   	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;
> > @@ -214,8 +369,10 @@ static int pvcalls_front_probe(struct xenbus_device
> > *dev,
> >   	if (ret < 0)
> >   		goto error;
> >   	bedata->ref = ref = gnttab_claim_grant_reference(&gref_head);
> > -	if (ref < 0)
> > +	if (ref < 0) {
> > +		ret = ref;
> >   		goto error;
> > +	}
> >   	gnttab_grant_foreign_access_ref(ref, dev->otherend_id,
> >   					virt_to_gfn((void *)sring), 0);
> >   @@ -246,8 +403,6 @@ static int pvcalls_front_probe(struct xenbus_device
> > *dev,
> >   	INIT_LIST_HEAD(&bedata->socket_mappings);
> >   	INIT_LIST_HEAD(&bedata->socketpass_mappings);
> >   	spin_lock_init(&bedata->pvcallss_lock);
> > -	dev_set_drvdata(&dev->dev, bedata);
> > -	pvcalls_front_dev = dev;
> >   	xenbus_switch_state(dev, XenbusStateInitialised);
> 
> Why are these changes made here and not in the original patch?

I made a mistake in updating the patches for v2 :-(
I'll fix it.


> >     	return 0;
> > 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
>