Commit eb76a9f1 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'xen-netback-rx-refactor' 



Paul Durrant says:

====================
xen-netback: guest rx side refactor

This series refactors the guest rx side of xen-netback:

- The code is moved into its own source module.

- The prefix variant of GSO handling is retired (since it is no longer
  in common use, and alternatives exist).

- The code is then simplified and modifications made to improve
  performance.

v2:
- Rebased onto refreshed net-next
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 00c06ed7 2167ca02

drivers/net/xen-netback/Makefile

+1 −1
Original line number Diff line number Diff line 
obj-$(CONFIG_XEN_NETDEV_BACKEND) := xen-netback.o



xen-netback-y := netback.o xenbus.o interface.o hash.o
 
xen-netback-y := netback.o xenbus.o interface.o hash.o rx.o

drivers/net/xen-netback/common.h

+11 −14
Original line number Diff line number Diff line
@@ -91,13 +91,6 @@ struct xenvif_rx_meta { 
 */

#define MAX_XEN_SKB_FRAGS (65536 / XEN_PAGE_SIZE + 1)



/* It's possible for an skb to have a maximal number of frags

 * but still be less than MAX_BUFFER_OFFSET in size. Thus the

 * worst-case number of copy operations is MAX_XEN_SKB_FRAGS per

 * ring slot.

 */

#define MAX_GRANT_COPY_OPS (MAX_XEN_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)



#define NETBACK_INVALID_HANDLE -1



/* To avoid confusion, we define XEN_NETBK_LEGACY_SLOTS_MAX indicating
@@ -133,6 +126,15 @@ struct xenvif_stats { 
	unsigned long tx_frag_overflow;

};



#define COPY_BATCH_SIZE 64



struct xenvif_copy_state {

	struct gnttab_copy op[COPY_BATCH_SIZE];

	RING_IDX idx[COPY_BATCH_SIZE];

	unsigned int num;

	struct sk_buff_head *completed;

};



struct xenvif_queue { /* Per-queue data for xenvif */

	unsigned int id; /* Queue ID, 0-based */

	char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
@@ -189,12 +191,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */ 
	unsigned long last_rx_time;

	bool stalled;



	struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];



	/* We create one meta structure per ring request we consume, so

	 * the maximum number is the same as the ring size.

	 */

	struct xenvif_rx_meta meta[XEN_NETIF_RX_RING_SIZE];

	struct xenvif_copy_state rx_copy;



	/* Transmit shaping: allow 'credit_bytes' every 'credit_usec'. */

	unsigned long   credit_bytes;
@@ -260,7 +257,6 @@ struct xenvif { 


	/* Frontend feature information. */

	int gso_mask;

	int gso_prefix_mask;



	u8 can_sg:1;

	u8 ip_csum:1;
@@ -359,6 +355,7 @@ int xenvif_dealloc_kthread(void *data); 


irqreturn_t xenvif_ctrl_irq_fn(int irq, void *data);



void xenvif_rx_action(struct xenvif_queue *queue);

void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb);



void xenvif_carrier_on(struct xenvif *vif);

drivers/net/xen-netback/interface.c

+3 −3
Original line number Diff line number Diff line
@@ -319,9 +319,9 @@ static netdev_features_t xenvif_fix_features(struct net_device *dev, 


	if (!vif->can_sg)

		features &= ~NETIF_F_SG;

	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV4))

	if (~(vif->gso_mask) & GSO_BIT(TCPV4))

		features &= ~NETIF_F_TSO;

	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV6))

	if (~(vif->gso_mask) & GSO_BIT(TCPV6))

		features &= ~NETIF_F_TSO6;

	if (!vif->ip_csum)

		features &= ~NETIF_F_IP_CSUM;
@@ -467,7 +467,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid, 
	dev->netdev_ops	= &xenvif_netdev_ops;

	dev->hw_features = NETIF_F_SG |

		NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |

		NETIF_F_TSO | NETIF_F_TSO6;

		NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_FRAGLIST;

	dev->features = dev->hw_features | NETIF_F_RXCSUM;

	dev->ethtool_ops = &xenvif_ethtool_ops;

drivers/net/xen-netback/netback.c

+0 −754
Original line number Diff line number Diff line
@@ -106,13 +106,6 @@ static void push_tx_responses(struct xenvif_queue *queue); 


static inline int tx_work_todo(struct xenvif_queue *queue);



static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue,

					     u16      id,

					     s8       st,

					     u16      offset,

					     u16      size,

					     u16      flags);



static inline unsigned long idx_to_pfn(struct xenvif_queue *queue,

				       u16 idx)

{
@@ -155,571 +148,11 @@ static inline pending_ring_idx_t pending_index(unsigned i) 
	return i & (MAX_PENDING_REQS-1);

}



static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)

{

	RING_IDX prod, cons;

	struct sk_buff *skb;

	int needed;



	skb = skb_peek(&queue->rx_queue);

	if (!skb)

		return false;



	needed = DIV_ROUND_UP(skb->len, XEN_PAGE_SIZE);

	if (skb_is_gso(skb))

		needed++;

	if (skb->sw_hash)

		needed++;



	do {

		prod = queue->rx.sring->req_prod;

		cons = queue->rx.req_cons;



		if (prod - cons >= needed)

			return true;



		queue->rx.sring->req_event = prod + 1;



		/* Make sure event is visible before we check prod

		 * again.

		 */

		mb();

	} while (queue->rx.sring->req_prod != prod);



	return false;

}



void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)

{

	unsigned long flags;



	spin_lock_irqsave(&queue->rx_queue.lock, flags);



	__skb_queue_tail(&queue->rx_queue, skb);



	queue->rx_queue_len += skb->len;

	if (queue->rx_queue_len > queue->rx_queue_max)

		netif_tx_stop_queue(netdev_get_tx_queue(queue->vif->dev, queue->id));



	spin_unlock_irqrestore(&queue->rx_queue.lock, flags);

}



static struct sk_buff *xenvif_rx_dequeue(struct xenvif_queue *queue)

{

	struct sk_buff *skb;



	spin_lock_irq(&queue->rx_queue.lock);



	skb = __skb_dequeue(&queue->rx_queue);

	if (skb)

		queue->rx_queue_len -= skb->len;



	spin_unlock_irq(&queue->rx_queue.lock);



	return skb;

}



static void xenvif_rx_queue_maybe_wake(struct xenvif_queue *queue)

{

	spin_lock_irq(&queue->rx_queue.lock);



	if (queue->rx_queue_len < queue->rx_queue_max)

		netif_tx_wake_queue(netdev_get_tx_queue(queue->vif->dev, queue->id));



	spin_unlock_irq(&queue->rx_queue.lock);

}





static void xenvif_rx_queue_purge(struct xenvif_queue *queue)

{

	struct sk_buff *skb;

	while ((skb = xenvif_rx_dequeue(queue)) != NULL)

		kfree_skb(skb);

}



static void xenvif_rx_queue_drop_expired(struct xenvif_queue *queue)

{

	struct sk_buff *skb;



	for(;;) {

		skb = skb_peek(&queue->rx_queue);

		if (!skb)

			break;

		if (time_before(jiffies, XENVIF_RX_CB(skb)->expires))

			break;

		xenvif_rx_dequeue(queue);

		kfree_skb(skb);

	}

}



struct netrx_pending_operations {

	unsigned copy_prod, copy_cons;

	unsigned meta_prod, meta_cons;

	struct gnttab_copy *copy;

	struct xenvif_rx_meta *meta;

	int copy_off;

	grant_ref_t copy_gref;

};



static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif_queue *queue,

						 struct netrx_pending_operations *npo)

{

	struct xenvif_rx_meta *meta;

	struct xen_netif_rx_request req;



	RING_COPY_REQUEST(&queue->rx, queue->rx.req_cons++, &req);



	meta = npo->meta + npo->meta_prod++;

	meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;

	meta->gso_size = 0;

	meta->size = 0;

	meta->id = req.id;



	npo->copy_off = 0;

	npo->copy_gref = req.gref;



	return meta;

}



struct gop_frag_copy {

	struct xenvif_queue *queue;

	struct netrx_pending_operations *npo;

	struct xenvif_rx_meta *meta;

	int head;

	int gso_type;

	int protocol;

	int hash_present;



	struct page *page;

};



static void xenvif_setup_copy_gop(unsigned long gfn,

				  unsigned int offset,

				  unsigned int *len,

				  struct gop_frag_copy *info)

{

	struct gnttab_copy *copy_gop;

	struct xen_page_foreign *foreign;

	/* Convenient aliases */

	struct xenvif_queue *queue = info->queue;

	struct netrx_pending_operations *npo = info->npo;

	struct page *page = info->page;



	BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);



	if (npo->copy_off == MAX_BUFFER_OFFSET)

		info->meta = get_next_rx_buffer(queue, npo);



	if (npo->copy_off + *len > MAX_BUFFER_OFFSET)

		*len = MAX_BUFFER_OFFSET - npo->copy_off;



	copy_gop = npo->copy + npo->copy_prod++;

	copy_gop->flags = GNTCOPY_dest_gref;

	copy_gop->len = *len;



	foreign = xen_page_foreign(page);

	if (foreign) {

		copy_gop->source.domid = foreign->domid;

		copy_gop->source.u.ref = foreign->gref;

		copy_gop->flags |= GNTCOPY_source_gref;

	} else {

		copy_gop->source.domid = DOMID_SELF;

		copy_gop->source.u.gmfn = gfn;

	}

	copy_gop->source.offset = offset;



	copy_gop->dest.domid = queue->vif->domid;

	copy_gop->dest.offset = npo->copy_off;

	copy_gop->dest.u.ref = npo->copy_gref;



	npo->copy_off += *len;

	info->meta->size += *len;



	if (!info->head)

		return;



	/* Leave a gap for the GSO descriptor. */

	if ((1 << info->gso_type) & queue->vif->gso_mask)

		queue->rx.req_cons++;



	/* Leave a gap for the hash extra segment. */

	if (info->hash_present)

		queue->rx.req_cons++;



	info->head = 0; /* There must be something in this buffer now */

}



static void xenvif_gop_frag_copy_grant(unsigned long gfn,

				       unsigned offset,

				       unsigned int len,

				       void *data)

{

	unsigned int bytes;



	while (len) {

		bytes = len;

		xenvif_setup_copy_gop(gfn, offset, &bytes, data);

		offset += bytes;

		len -= bytes;

	}

}



/*

 * Set up the grant operations for this fragment. If it's a flipping

 * interface, we also set up the unmap request from here.

 */

static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb,

				 struct netrx_pending_operations *npo,

				 struct page *page, unsigned long size,

				 unsigned long offset, int *head)

{

	struct gop_frag_copy info = {

		.queue = queue,

		.npo = npo,

		.head = *head,

		.gso_type = XEN_NETIF_GSO_TYPE_NONE,

		/* xenvif_set_skb_hash() will have either set a s/w

		 * hash or cleared the hash depending on

		 * whether the the frontend wants a hash for this skb.

		 */

		.hash_present = skb->sw_hash,

	};

	unsigned long bytes;



	if (skb_is_gso(skb)) {

		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)

			info.gso_type = XEN_NETIF_GSO_TYPE_TCPV4;

		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)

			info.gso_type = XEN_NETIF_GSO_TYPE_TCPV6;

	}



	/* Data must not cross a page boundary. */

	BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));



	info.meta = npo->meta + npo->meta_prod - 1;



	/* Skip unused frames from start of page */

	page += offset >> PAGE_SHIFT;

	offset &= ~PAGE_MASK;



	while (size > 0) {

		BUG_ON(offset >= PAGE_SIZE);



		bytes = PAGE_SIZE - offset;

		if (bytes > size)

			bytes = size;



		info.page = page;

		gnttab_foreach_grant_in_range(page, offset, bytes,

					      xenvif_gop_frag_copy_grant,

					      &info);

		size -= bytes;

		offset = 0;



		/* Next page */

		if (size) {

			BUG_ON(!PageCompound(page));

			page++;

		}

	}



	*head = info.head;

}



/*

 * Prepare an SKB to be transmitted to the frontend.

 *

 * This function is responsible for allocating grant operations, meta

 * structures, etc.

 *

 * It returns the number of meta structures consumed. The number of

 * ring slots used is always equal to the number of meta slots used

 * plus the number of GSO descriptors used. Currently, we use either

 * zero GSO descriptors (for non-GSO packets) or one descriptor (for

 * frontend-side LRO).

 */

static int xenvif_gop_skb(struct sk_buff *skb,

			  struct netrx_pending_operations *npo,

			  struct xenvif_queue *queue)

{

	struct xenvif *vif = netdev_priv(skb->dev);

	int nr_frags = skb_shinfo(skb)->nr_frags;

	int i;

	struct xen_netif_rx_request req;

	struct xenvif_rx_meta *meta;

	unsigned char *data;

	int head = 1;

	int old_meta_prod;

	int gso_type;



	old_meta_prod = npo->meta_prod;



	gso_type = XEN_NETIF_GSO_TYPE_NONE;

	if (skb_is_gso(skb)) {

		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)

			gso_type = XEN_NETIF_GSO_TYPE_TCPV4;

		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)

			gso_type = XEN_NETIF_GSO_TYPE_TCPV6;

	}



	/* Set up a GSO prefix descriptor, if necessary */

	if ((1 << gso_type) & vif->gso_prefix_mask) {

		RING_COPY_REQUEST(&queue->rx, queue->rx.req_cons++, &req);

		meta = npo->meta + npo->meta_prod++;

		meta->gso_type = gso_type;

		meta->gso_size = skb_shinfo(skb)->gso_size;

		meta->size = 0;

		meta->id = req.id;

	}



	RING_COPY_REQUEST(&queue->rx, queue->rx.req_cons++, &req);

	meta = npo->meta + npo->meta_prod++;



	if ((1 << gso_type) & vif->gso_mask) {

		meta->gso_type = gso_type;

		meta->gso_size = skb_shinfo(skb)->gso_size;

	} else {

		meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;

		meta->gso_size = 0;

	}



	meta->size = 0;

	meta->id = req.id;

	npo->copy_off = 0;

	npo->copy_gref = req.gref;



	data = skb->data;

	while (data < skb_tail_pointer(skb)) {

		unsigned int offset = offset_in_page(data);

		unsigned int len = PAGE_SIZE - offset;



		if (data + len > skb_tail_pointer(skb))

			len = skb_tail_pointer(skb) - data;



		xenvif_gop_frag_copy(queue, skb, npo,

				     virt_to_page(data), len, offset, &head);

		data += len;

	}



	for (i = 0; i < nr_frags; i++) {

		xenvif_gop_frag_copy(queue, skb, npo,

				     skb_frag_page(&skb_shinfo(skb)->frags[i]),

				     skb_frag_size(&skb_shinfo(skb)->frags[i]),

				     skb_shinfo(skb)->frags[i].page_offset,

				     &head);

	}



	return npo->meta_prod - old_meta_prod;

}



/*

 * This is a twin to xenvif_gop_skb.  Assume that xenvif_gop_skb was

 * used to set up the operations on the top of

 * netrx_pending_operations, which have since been done.  Check that

 * they didn't give any errors and advance over them.

 */

static int xenvif_check_gop(struct xenvif *vif, int nr_meta_slots,

			    struct netrx_pending_operations *npo)

{

	struct gnttab_copy     *copy_op;

	int status = XEN_NETIF_RSP_OKAY;

	int i;



	for (i = 0; i < nr_meta_slots; i++) {

		copy_op = npo->copy + npo->copy_cons++;

		if (copy_op->status != GNTST_okay) {

			netdev_dbg(vif->dev,

				   "Bad status %d from copy to DOM%d.\n",

				   copy_op->status, vif->domid);

			status = XEN_NETIF_RSP_ERROR;

		}

	}



	return status;

}



static void xenvif_add_frag_responses(struct xenvif_queue *queue, int status,

				      struct xenvif_rx_meta *meta,

				      int nr_meta_slots)

{

	int i;

	unsigned long offset;



	/* No fragments used */

	if (nr_meta_slots <= 1)

		return;



	nr_meta_slots--;



	for (i = 0; i < nr_meta_slots; i++) {

		int flags;

		if (i == nr_meta_slots - 1)

			flags = 0;

		else

			flags = XEN_NETRXF_more_data;



		offset = 0;

		make_rx_response(queue, meta[i].id, status, offset,

				 meta[i].size, flags);

	}

}



void xenvif_kick_thread(struct xenvif_queue *queue)

{

	wake_up(&queue->wq);

}



static void xenvif_rx_action(struct xenvif_queue *queue)

{

	struct xenvif *vif = queue->vif;

	s8 status;

	u16 flags;

	struct xen_netif_rx_response *resp;

	struct sk_buff_head rxq;

	struct sk_buff *skb;

	LIST_HEAD(notify);

	int ret;

	unsigned long offset;

	bool need_to_notify = false;



	struct netrx_pending_operations npo = {

		.copy  = queue->grant_copy_op,

		.meta  = queue->meta,

	};



	skb_queue_head_init(&rxq);



	while (xenvif_rx_ring_slots_available(queue)

	       && (skb = xenvif_rx_dequeue(queue)) != NULL) {

		queue->last_rx_time = jiffies;



		XENVIF_RX_CB(skb)->meta_slots_used = xenvif_gop_skb(skb, &npo, queue);



		__skb_queue_tail(&rxq, skb);

	}



	BUG_ON(npo.meta_prod > ARRAY_SIZE(queue->meta));



	if (!npo.copy_prod)

		goto done;



	BUG_ON(npo.copy_prod > MAX_GRANT_COPY_OPS);

	gnttab_batch_copy(queue->grant_copy_op, npo.copy_prod);



	while ((skb = __skb_dequeue(&rxq)) != NULL) {

		struct xen_netif_extra_info *extra = NULL;



		if ((1 << queue->meta[npo.meta_cons].gso_type) &

		    vif->gso_prefix_mask) {

			resp = RING_GET_RESPONSE(&queue->rx,

						 queue->rx.rsp_prod_pvt++);



			resp->flags = XEN_NETRXF_gso_prefix | XEN_NETRXF_more_data;



			resp->offset = queue->meta[npo.meta_cons].gso_size;

			resp->id = queue->meta[npo.meta_cons].id;

			resp->status = XENVIF_RX_CB(skb)->meta_slots_used;



			npo.meta_cons++;

			XENVIF_RX_CB(skb)->meta_slots_used--;

		}





		queue->stats.tx_bytes += skb->len;

		queue->stats.tx_packets++;



		status = xenvif_check_gop(vif,

					  XENVIF_RX_CB(skb)->meta_slots_used,

					  &npo);



		if (XENVIF_RX_CB(skb)->meta_slots_used == 1)

			flags = 0;

		else

			flags = XEN_NETRXF_more_data;



		if (skb->ip_summed == CHECKSUM_PARTIAL) /* local packet? */

			flags |= XEN_NETRXF_csum_blank | XEN_NETRXF_data_validated;

		else if (skb->ip_summed == CHECKSUM_UNNECESSARY)

			/* remote but checksummed. */

			flags |= XEN_NETRXF_data_validated;



		offset = 0;

		resp = make_rx_response(queue, queue->meta[npo.meta_cons].id,

					status, offset,

					queue->meta[npo.meta_cons].size,

					flags);



		if ((1 << queue->meta[npo.meta_cons].gso_type) &

		    vif->gso_mask) {

			extra = (struct xen_netif_extra_info *)

				RING_GET_RESPONSE(&queue->rx,

						  queue->rx.rsp_prod_pvt++);



			resp->flags |= XEN_NETRXF_extra_info;



			extra->u.gso.type = queue->meta[npo.meta_cons].gso_type;

			extra->u.gso.size = queue->meta[npo.meta_cons].gso_size;

			extra->u.gso.pad = 0;

			extra->u.gso.features = 0;



			extra->type = XEN_NETIF_EXTRA_TYPE_GSO;

			extra->flags = 0;

		}



		if (skb->sw_hash) {

			/* Since the skb got here via xenvif_select_queue()

			 * we know that the hash has been re-calculated

			 * according to a configuration set by the frontend

			 * and therefore we know that it is legitimate to

			 * pass it to the frontend.

			 */

			if (resp->flags & XEN_NETRXF_extra_info)

				extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;

			else

				resp->flags |= XEN_NETRXF_extra_info;



			extra = (struct xen_netif_extra_info *)

				RING_GET_RESPONSE(&queue->rx,

						  queue->rx.rsp_prod_pvt++);



			extra->u.hash.algorithm =

				XEN_NETIF_CTRL_HASH_ALGORITHM_TOEPLITZ;



			if (skb->l4_hash)

				extra->u.hash.type =

					skb->protocol == htons(ETH_P_IP) ?

					_XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP :

					_XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP;

			else

				extra->u.hash.type =

					skb->protocol == htons(ETH_P_IP) ?

					_XEN_NETIF_CTRL_HASH_TYPE_IPV4 :

					_XEN_NETIF_CTRL_HASH_TYPE_IPV6;



			*(uint32_t *)extra->u.hash.value =

				skb_get_hash_raw(skb);



			extra->type = XEN_NETIF_EXTRA_TYPE_HASH;

			extra->flags = 0;

		}



		xenvif_add_frag_responses(queue, status,

					  queue->meta + npo.meta_cons + 1,

					  XENVIF_RX_CB(skb)->meta_slots_used);



		RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->rx, ret);



		need_to_notify |= !!ret;



		npo.meta_cons += XENVIF_RX_CB(skb)->meta_slots_used;

		dev_kfree_skb(skb);

	}



done:

	if (need_to_notify)

		notify_remote_via_irq(queue->rx_irq);

}



void xenvif_napi_schedule_or_enable_events(struct xenvif_queue *queue)

{

	int more_to_do;
@@ -1951,29 +1384,6 @@ static void push_tx_responses(struct xenvif_queue *queue) 
		notify_remote_via_irq(queue->tx_irq);

}



static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue,

					     u16      id,

					     s8       st,

					     u16      offset,

					     u16      size,

					     u16      flags)

{

	RING_IDX i = queue->rx.rsp_prod_pvt;

	struct xen_netif_rx_response *resp;



	resp = RING_GET_RESPONSE(&queue->rx, i);

	resp->offset     = offset;

	resp->flags      = flags;

	resp->id         = id;

	resp->status     = (s16)size;

	if (st < 0)

		resp->status = (s16)st;



	queue->rx.rsp_prod_pvt = ++i;



	return resp;

}



void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx)

{

	int ret;
@@ -2055,170 +1465,6 @@ err: 
	return err;

}



static void xenvif_queue_carrier_off(struct xenvif_queue *queue)

{

	struct xenvif *vif = queue->vif;



	queue->stalled = true;



	/* At least one queue has stalled? Disable the carrier. */

	spin_lock(&vif->lock);

	if (vif->stalled_queues++ == 0) {

		netdev_info(vif->dev, "Guest Rx stalled");

		netif_carrier_off(vif->dev);

	}

	spin_unlock(&vif->lock);

}



static void xenvif_queue_carrier_on(struct xenvif_queue *queue)

{

	struct xenvif *vif = queue->vif;



	queue->last_rx_time = jiffies; /* Reset Rx stall detection. */

	queue->stalled = false;



	/* All queues are ready? Enable the carrier. */

	spin_lock(&vif->lock);

	if (--vif->stalled_queues == 0) {

		netdev_info(vif->dev, "Guest Rx ready");

		netif_carrier_on(vif->dev);

	}

	spin_unlock(&vif->lock);

}



static bool xenvif_rx_queue_stalled(struct xenvif_queue *queue)

{

	RING_IDX prod, cons;



	prod = queue->rx.sring->req_prod;

	cons = queue->rx.req_cons;



	return !queue->stalled && prod - cons < 1

		&& time_after(jiffies,

			      queue->last_rx_time + queue->vif->stall_timeout);

}



static bool xenvif_rx_queue_ready(struct xenvif_queue *queue)

{

	RING_IDX prod, cons;



	prod = queue->rx.sring->req_prod;

	cons = queue->rx.req_cons;



	return queue->stalled && prod - cons >= 1;

}



static bool xenvif_have_rx_work(struct xenvif_queue *queue)

{

	return xenvif_rx_ring_slots_available(queue)

		|| (queue->vif->stall_timeout &&

		    (xenvif_rx_queue_stalled(queue)

		     || xenvif_rx_queue_ready(queue)))

		|| kthread_should_stop()

		|| queue->vif->disabled;

}



static long xenvif_rx_queue_timeout(struct xenvif_queue *queue)

{

	struct sk_buff *skb;

	long timeout;



	skb = skb_peek(&queue->rx_queue);

	if (!skb)

		return MAX_SCHEDULE_TIMEOUT;



	timeout = XENVIF_RX_CB(skb)->expires - jiffies;

	return timeout < 0 ? 0 : timeout;

}



/* Wait until the guest Rx thread has work.

 *

 * The timeout needs to be adjusted based on the current head of the

 * queue (and not just the head at the beginning).  In particular, if

 * the queue is initially empty an infinite timeout is used and this

 * needs to be reduced when a skb is queued.

 *

 * This cannot be done with wait_event_timeout() because it only

 * calculates the timeout once.

 */

static void xenvif_wait_for_rx_work(struct xenvif_queue *queue)

{

	DEFINE_WAIT(wait);



	if (xenvif_have_rx_work(queue))

		return;



	for (;;) {

		long ret;



		prepare_to_wait(&queue->wq, &wait, TASK_INTERRUPTIBLE);

		if (xenvif_have_rx_work(queue))

			break;

		ret = schedule_timeout(xenvif_rx_queue_timeout(queue));

		if (!ret)

			break;

	}

	finish_wait(&queue->wq, &wait);

}



int xenvif_kthread_guest_rx(void *data)

{

	struct xenvif_queue *queue = data;

	struct xenvif *vif = queue->vif;



	if (!vif->stall_timeout)

		xenvif_queue_carrier_on(queue);



	for (;;) {

		xenvif_wait_for_rx_work(queue);



		if (kthread_should_stop())

			break;



		/* This frontend is found to be rogue, disable it in

		 * kthread context. Currently this is only set when

		 * netback finds out frontend sends malformed packet,

		 * but we cannot disable the interface in softirq

		 * context so we defer it here, if this thread is

		 * associated with queue 0.

		 */

		if (unlikely(vif->disabled && queue->id == 0)) {

			xenvif_carrier_off(vif);

			break;

		}



		if (!skb_queue_empty(&queue->rx_queue))

			xenvif_rx_action(queue);



		/* If the guest hasn't provided any Rx slots for a

		 * while it's probably not responsive, drop the

		 * carrier so packets are dropped earlier.

		 */

		if (vif->stall_timeout) {

			if (xenvif_rx_queue_stalled(queue))

				xenvif_queue_carrier_off(queue);

			else if (xenvif_rx_queue_ready(queue))

				xenvif_queue_carrier_on(queue);

		}



		/* Queued packets may have foreign pages from other

		 * domains.  These cannot be queued indefinitely as

		 * this would starve guests of grant refs and transmit

		 * slots.

		 */

		xenvif_rx_queue_drop_expired(queue);



		xenvif_rx_queue_maybe_wake(queue);



		cond_resched();

	}



	/* Bin any remaining skbs */

	xenvif_rx_queue_purge(queue);



	return 0;

}



static bool xenvif_dealloc_kthread_should_stop(struct xenvif_queue *queue)

{

	/* Dealloc thread must remain running until all inflight

drivers/net/xen-netback/rx.c

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