Merge tag 'for-linus-4.10-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:
 "Xen features and fixes for 4.10

  These are some fixes, a move of some arm related headers to share them
  between arm and arm64 and a series introducing a helper to make code
  more readable.

  The most notable change is David stepping down as maintainer of the
  Xen hypervisor interface. This results in me sending you the pull
  requests for Xen related code from now on"

* tag 'for-linus-4.10-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (29 commits)
  xen/balloon: Only mark a page as managed when it is released
  xenbus: fix deadlock on writes to /proc/xen/xenbus
  xen/scsifront: don't request a slot on the ring until request is ready
  xen/x86: Increase xen_e820_map to E820_X_MAX possible entries
  x86: Make E820_X_MAX unconditionally larger than E820MAX
  xen/pci: Bubble up error and fix description.
  xen: xenbus: set error code on failure
  xen: set error code on failures
  arm/xen: Use alloc_percpu rather than __alloc_percpu
  arm/arm64: xen: Move shared architecture headers to include/xen/arm
  xen/events: use xen_vcpu_id mapping for EVTCHNOP_status
  xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
  xen-scsifront: Add a missing call to kfree
  MAINTAINERS: update XEN HYPERVISOR INTERFACE
  xenfs: Use proc_create_mount_point() to create /proc/xen
  xen-platform: use builtin_pci_driver
  xen-netback: fix error handling output
  xen: make use of xenbus_read_unsigned() in xenbus
  xen: make use of xenbus_read_unsigned() in xen-pciback
  xen: make use of xenbus_read_unsigned() in xen-fbfront
  ...

19 files changed, 207 insertions, 331 deletions

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 3cc6d1d86f1e..415e79b69d34 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -533,13 +533,11 @@ static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info
 	struct xenbus_device *dev = be->dev;
 	struct xen_blkif *blkif = be->blkif;
 	int err;
-	int state = 0, discard_enable;
+	int state = 0;
 	struct block_device *bdev = be->blkif->vbd.bdev;
 	struct request_queue *q = bdev_get_queue(bdev);
 
-	err = xenbus_scanf(XBT_NIL, dev->nodename, "discard-enable", "%d",
-			   &discard_enable);
-	if (err == 1 && !discard_enable)
+	if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
 		return;
 
 	if (blk_queue_discard(q)) {
@@ -1039,30 +1037,24 @@ static int connect_ring(struct backend_info *be)
 		xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 		return -ENOSYS;
 	}
-	err = xenbus_scanf(XBT_NIL, dev->otherend,
-			   "feature-persistent", "%u", &pers_grants);
-	if (err <= 0)
-		pers_grants = 0;
-
+	pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
+					   0);
 	be->blkif->vbd.feature_gnt_persistent = pers_grants;
 	be->blkif->vbd.overflow_max_grants = 0;
 
 	/*
 	 * Read the number of hardware queues from frontend.
 	 */
-	err = xenbus_scanf(XBT_NIL, dev->otherend, "multi-queue-num-queues",
-			   "%u", &requested_num_queues);
-	if (err < 0) {
-		requested_num_queues = 1;
-	} else {
-		if (requested_num_queues > xenblk_max_queues
-		    || requested_num_queues == 0) {
-			/* Buggy or malicious guest. */
-			xenbus_dev_fatal(dev, err,
-					"guest requested %u queues, exceeding the maximum of %u.",
-					requested_num_queues, xenblk_max_queues);
-			return -ENOSYS;
-		}
+	requested_num_queues = xenbus_read_unsigned(dev->otherend,
+						    "multi-queue-num-queues",
+						    1);
+	if (requested_num_queues > xenblk_max_queues
+	    || requested_num_queues == 0) {
+		/* Buggy or malicious guest. */
+		xenbus_dev_fatal(dev, err,
+				"guest requested %u queues, exceeding the maximum of %u.",
+				requested_num_queues, xenblk_max_queues);
+		return -ENOSYS;
 	}
 	be->blkif->nr_rings = requested_num_queues;
 	if (xen_blkif_alloc_rings(be->blkif))
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index c000fdf048b2..b2bdfa81f929 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1758,17 +1758,13 @@ static int talk_to_blkback(struct xenbus_device *dev,
 	const char *message = NULL;
 	struct xenbus_transaction xbt;
 	int err;
-	unsigned int i, max_page_order = 0;
-	unsigned int ring_page_order = 0;
+	unsigned int i, max_page_order;
+	unsigned int ring_page_order;
 
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "max-ring-page-order", "%u", &max_page_order);
-	if (err != 1)
-		info->nr_ring_pages = 1;
-	else {
-		ring_page_order = min(xen_blkif_max_ring_order, max_page_order);
-		info->nr_ring_pages = 1 << ring_page_order;
-	}
+	max_page_order = xenbus_read_unsigned(info->xbdev->otherend,
+					      "max-ring-page-order", 0);
+	ring_page_order = min(xen_blkif_max_ring_order, max_page_order);
+	info->nr_ring_pages = 1 << ring_page_order;
 
 	for (i = 0; i < info->nr_rings; i++) {
 		struct blkfront_ring_info *rinfo = &info->rinfo[i];
@@ -1877,18 +1873,14 @@ again:
 
 static int negotiate_mq(struct blkfront_info *info)
 {
-	unsigned int backend_max_queues = 0;
-	int err;
+	unsigned int backend_max_queues;
 	unsigned int i;
 
 	BUG_ON(info->nr_rings);
 
 	/* Check if backend supports multiple queues. */
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "multi-queue-max-queues", "%u", &backend_max_queues);
-	if (err < 0)
-		backend_max_queues = 1;
-
+	backend_max_queues = xenbus_read_unsigned(info->xbdev->otherend,
+						  "multi-queue-max-queues", 1);
 	info->nr_rings = min(backend_max_queues, xen_blkif_max_queues);
 	/* We need at least one ring. */
 	if (!info->nr_rings)
@@ -2196,7 +2188,6 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 	int err;
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
-	unsigned int discard_secure;
 
 	info->feature_discard = 1;
 	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
@@ -2207,10 +2198,9 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 		info->discard_granularity = discard_granularity;
 		info->discard_alignment = discard_alignment;
 	}
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "discard-secure", "%u", &discard_secure);
-	if (err > 0)
-		info->feature_secdiscard = !!discard_secure;
+	info->feature_secdiscard =
+		!!xenbus_read_unsigned(info->xbdev->otherend, "discard-secure",
+				       0);
 }
 
 static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
@@ -2302,16 +2292,11 @@ out_of_memory:
  */
 static void blkfront_gather_backend_features(struct blkfront_info *info)
 {
-	int err;
-	int barrier, flush, discard, persistent;
 	unsigned int indirect_segments;
 
 	info->feature_flush = 0;
 	info->feature_fua = 0;
 
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "feature-barrier", "%d", &barrier);
-
 	/*
 	 * If there's no "feature-barrier" defined, then it means
 	 * we're dealing with a very old backend which writes
@@ -2319,7 +2304,7 @@ static void blkfront_gather_backend_features(struct blkfront_info *info)
 	 *
 	 * If there are barriers, then we use flush.
 	 */
-	if (err > 0 && barrier) {
+	if (xenbus_read_unsigned(info->xbdev->otherend, "feature-barrier", 0)) {
 		info->feature_flush = 1;
 		info->feature_fua = 1;
 	}
@@ -2328,35 +2313,23 @@ static void blkfront_gather_backend_features(struct blkfront_info *info)
 	 * And if there is "feature-flush-cache" use that above
 	 * barriers.
 	 */
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "feature-flush-cache", "%d", &flush);
-
-	if (err > 0 && flush) {
+	if (xenbus_read_unsigned(info->xbdev->otherend, "feature-flush-cache",
+				 0)) {
 		info->feature_flush = 1;
 		info->feature_fua = 0;
 	}
 
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "feature-discard", "%d", &discard);
-
-	if (err > 0 && discard)
+	if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0))
 		blkfront_setup_discard(info);
 
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "feature-persistent", "%d", &persistent);
-	if (err <= 0)
-		info->feature_persistent = 0;
-	else
-		info->feature_persistent = persistent;
+	info->feature_persistent =
+		xenbus_read_unsigned(info->xbdev->otherend,
+				     "feature-persistent", 0);
 
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "feature-max-indirect-segments", "%u",
-			   &indirect_segments);
-	if (err <= 0)
-		info->max_indirect_segments = 0;
-	else
-		info->max_indirect_segments = min(indirect_segments,
-						  xen_blkif_max_segments);
+	indirect_segments = xenbus_read_unsigned(info->xbdev->otherend,
+					"feature-max-indirect-segments", 0);
+	info->max_indirect_segments = min(indirect_segments,
+					  xen_blkif_max_segments);
 }
 
 /*
@@ -2421,11 +2394,9 @@ static void blkfront_connect(struct blkfront_info *info)
 	 * provide this. Assume physical sector size to be the same as
 	 * sector_size in that case.
 	 */
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "physical-sector-size", "%u", &physical_sector_size);
-	if (err != 1)
-		physical_sector_size = sector_size;
-
+	physical_sector_size = xenbus_read_unsigned(info->xbdev->otherend,
+						    "physical-sector-size",
+						    sector_size);
 	blkfront_gather_backend_features(info);
 	for (i = 0; i < info->nr_rings; i++) {
 		err = blkfront_setup_indirect(&info->rinfo[i]);
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
index 62028f483bba..50072cc4fe5c 100644
--- a/drivers/char/tpm/xen-tpmfront.c
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -337,18 +337,14 @@ static int tpmfront_resume(struct xenbus_device *dev)
 static void backend_changed(struct xenbus_device *dev,
 		enum xenbus_state backend_state)
 {
-	int val;
-
 	switch (backend_state) {
 	case XenbusStateInitialised:
 	case XenbusStateConnected:
 		if (dev->state == XenbusStateConnected)
 			break;
 
-		if (xenbus_scanf(XBT_NIL, dev->otherend,
-				"feature-protocol-v2", "%d", &val) < 0)
-			val = 0;
-		if (!val) {
+		if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
+					  0)) {
 			xenbus_dev_fatal(dev, -EINVAL,
 					"vTPM protocol 2 required");
 			return;
diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
index 227fbd2dbb71..3900875dec10 100644
--- a/drivers/input/misc/xen-kbdfront.c
+++ b/drivers/input/misc/xen-kbdfront.c
@@ -108,7 +108,8 @@ static irqreturn_t input_handler(int rq, void *dev_id)
 static int xenkbd_probe(struct xenbus_device *dev,
 				  const struct xenbus_device_id *id)
 {
-	int ret, i, abs;
+	int ret, i;
+	unsigned int abs;
 	struct xenkbd_info *info;
 	struct input_dev *kbd, *ptr;
 
@@ -127,8 +128,7 @@ static int xenkbd_probe(struct xenbus_device *dev,
 	if (!info->page)
 		goto error_nomem;
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-abs-pointer", "%d", &abs) < 0)
-		abs = 0;
+	abs = xenbus_read_unsigned(dev->otherend, "feature-abs-pointer", 0);
 	if (abs) {
 		ret = xenbus_write(XBT_NIL, dev->nodename,
 				   "request-abs-pointer", "1");
@@ -322,11 +322,8 @@ static void xenkbd_backend_changed(struct xenbus_device *dev,
 
 	case XenbusStateInitWait:
 InitWait:
-		ret = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-				   "feature-abs-pointer", "%d", &val);
-		if (ret < 0)
-			val = 0;
-		if (val) {
+		if (xenbus_read_unsigned(info->xbdev->otherend,
+					 "feature-abs-pointer", 0)) {
 			ret = xenbus_write(XBT_NIL, info->xbdev->nodename,
 					   "request-abs-pointer", "1");
 			if (ret)
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 55a4488633e4..3124eaec9427 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -785,12 +785,9 @@ static void xen_mcast_ctrl_changed(struct xenbus_watch *watch,
 	struct xenvif *vif = container_of(watch, struct xenvif,
 					  mcast_ctrl_watch);
 	struct xenbus_device *dev = xenvif_to_xenbus_device(vif);
-	int val;
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend,
-			 "request-multicast-control", "%d", &val) < 0)
-		val = 0;
-	vif->multicast_control = !!val;
+	vif->multicast_control = !!xenbus_read_unsigned(dev->otherend,
+					"request-multicast-control", 0);
 }
 
 static int xen_register_mcast_ctrl_watch(struct xenbus_device *dev,
@@ -934,14 +931,11 @@ static void connect(struct backend_info *be)
 	/* Check whether the frontend requested multiple queues
 	 * and read the number requested.
 	 */
-	err = xenbus_scanf(XBT_NIL, dev->otherend,
-			   "multi-queue-num-queues",
-			   "%u", &requested_num_queues);
-	if (err < 0) {
-		requested_num_queues = 1; /* Fall back to single queue */
-	} else if (requested_num_queues > xenvif_max_queues) {
+	requested_num_queues = xenbus_read_unsigned(dev->otherend,
+					"multi-queue-num-queues", 1);
+	if (requested_num_queues > xenvif_max_queues) {
 		/* buggy or malicious guest */
-		xenbus_dev_fatal(dev, err,
+		xenbus_dev_fatal(dev, -EINVAL,
 				 "guest requested %u queues, exceeding the maximum of %u.",
 				 requested_num_queues, xenvif_max_queues);
 		return;
@@ -1134,7 +1128,7 @@ static int read_xenbus_vif_flags(struct backend_info *be)
 	struct xenvif *vif = be->vif;
 	struct xenbus_device *dev = be->dev;
 	unsigned int rx_copy;
-	int err, val;
+	int err;
 
 	err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy", "%u",
 			   &rx_copy);
@@ -1150,10 +1144,7 @@ static int read_xenbus_vif_flags(struct backend_info *be)
 	if (!rx_copy)
 		return -EOPNOTSUPP;
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend,
-			 "feature-rx-notify", "%d", &val) < 0)
-		val = 0;
-	if (!val) {
+	if (!xenbus_read_unsigned(dev->otherend, "feature-rx-notify", 0)) {
 		/* - Reduce drain timeout to poll more frequently for
 		 *   Rx requests.
 		 * - Disable Rx stall detection.
@@ -1162,34 +1153,21 @@ static int read_xenbus_vif_flags(struct backend_info *be)
 		be->vif->stall_timeout = 0;
 	}
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",
-			 "%d", &val) < 0)
-		val = 0;
-	vif->can_sg = !!val;
+	vif->can_sg = !!xenbus_read_unsigned(dev->otherend, "feature-sg", 0);
 
 	vif->gso_mask = 0;
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
-			 "%d", &val) < 0)
-		val = 0;
-	if (val)
+	if (xenbus_read_unsigned(dev->otherend, "feature-gso-tcpv4", 0))
 		vif->gso_mask |= GSO_BIT(TCPV4);
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
-			 "%d", &val) < 0)
-		val = 0;
-	if (val)
+	if (xenbus_read_unsigned(dev->otherend, "feature-gso-tcpv6", 0))
 		vif->gso_mask |= GSO_BIT(TCPV6);
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
-			 "%d", &val) < 0)
-		val = 0;
-	vif->ip_csum = !val;
+	vif->ip_csum = !xenbus_read_unsigned(dev->otherend,
+					     "feature-no-csum-offload", 0);
 
-	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
-			 "%d", &val) < 0)
-		val = 0;
-	vif->ipv6_csum = !!val;
+	vif->ipv6_csum = !!xenbus_read_unsigned(dev->otherend,
+						"feature-ipv6-csum-offload", 0);
 
 	return 0;
 }
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index e085c8c31cfe..a479cd99911d 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1169,43 +1169,23 @@ static netdev_features_t xennet_fix_features(struct net_device *dev,
 	netdev_features_t features)
 {
 	struct netfront_info *np = netdev_priv(dev);
-	int val;
 
-	if (features & NETIF_F_SG) {
-		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend, "feature-sg",
-				 "%d", &val) < 0)
-			val = 0;
+	if (features & NETIF_F_SG &&
+	    !xenbus_read_unsigned(np->xbdev->otherend, "feature-sg", 0))
+		features &= ~NETIF_F_SG;
 
-		if (!val)
-			features &= ~NETIF_F_SG;
-	}
-
-	if (features & NETIF_F_IPV6_CSUM) {
-		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
-				 "feature-ipv6-csum-offload", "%d", &val) < 0)
-			val = 0;
-
-		if (!val)
-			features &= ~NETIF_F_IPV6_CSUM;
-	}
-
-	if (features & NETIF_F_TSO) {
-		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
-				 "feature-gso-tcpv4", "%d", &val) < 0)
-			val = 0;
+	if (features & NETIF_F_IPV6_CSUM &&
+	    !xenbus_read_unsigned(np->xbdev->otherend,
+				  "feature-ipv6-csum-offload", 0))
+		features &= ~NETIF_F_IPV6_CSUM;
 
-		if (!val)
-			features &= ~NETIF_F_TSO;
-	}
+	if (features & NETIF_F_TSO &&
+	    !xenbus_read_unsigned(np->xbdev->otherend, "feature-gso-tcpv4", 0))
+		features &= ~NETIF_F_TSO;
 
-	if (features & NETIF_F_TSO6) {
-		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
-				 "feature-gso-tcpv6", "%d", &val) < 0)
-			val = 0;
-
-		if (!val)
-			features &= ~NETIF_F_TSO6;
-	}
+	if (features & NETIF_F_TSO6 &&
+	    !xenbus_read_unsigned(np->xbdev->otherend, "feature-gso-tcpv6", 0))
+		features &= ~NETIF_F_TSO6;
 
 	return features;
 }
@@ -1823,18 +1803,13 @@ static int talk_to_netback(struct xenbus_device *dev,
 	info->netdev->irq = 0;
 
 	/* Check if backend supports multiple queues */
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "multi-queue-max-queues", "%u", &max_queues);
-	if (err < 0)
-		max_queues = 1;
+	max_queues = xenbus_read_unsigned(info->xbdev->otherend,
+					  "multi-queue-max-queues", 1);
 	num_queues = min(max_queues, xennet_max_queues);
 
 	/* Check feature-split-event-channels */
-	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-			   "feature-split-event-channels", "%u",
-			   &feature_split_evtchn);
-	if (err < 0)
-		feature_split_evtchn = 0;
+	feature_split_evtchn = xenbus_read_unsigned(info->xbdev->otherend,
+					"feature-split-event-channels", 0);
 
 	/* Read mac addr. */
 	err = xen_net_read_mac(dev, info->netdev->dev_addr);
@@ -1968,16 +1943,10 @@ static int xennet_connect(struct net_device *dev)
 	struct netfront_info *np = netdev_priv(dev);
 	unsigned int num_queues = 0;
 	int err;
-	unsigned int feature_rx_copy;
 	unsigned int j = 0;
 	struct netfront_queue *queue = NULL;
 
-	err = xenbus_scanf(XBT_NIL, np->xbdev->otherend,
-			   "feature-rx-copy", "%u", &feature_rx_copy);
-	if (err != 1)
-		feature_rx_copy = 0;
-
-	if (!feature_rx_copy) {
+	if (!xenbus_read_unsigned(np->xbdev->otherend, "feature-rx-copy", 0)) {
 		dev_info(&dev->dev,
 			 "backend does not support copying receive path\n");
 		return -ENODEV;
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index d6ff5e82377d..8fc2e9532575 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -1038,10 +1038,8 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
 			err = -ENOMEM;
 			goto out;
 		}
-		err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend, str, "%d",
-				   &state);
-		if (err != 1)
-			state = XenbusStateUnknown;
+		state = xenbus_read_unsigned(pdev->xdev->otherend, str,
+					     XenbusStateUnknown);
 
 		if (state != XenbusStateClosing)
 			continue;
diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
index 9dc8687bf048..9aa1fe1fc939 100644
--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -79,10 +79,13 @@
 struct vscsifrnt_shadow {
 	/* command between backend and frontend */
 	unsigned char act;
+	uint8_t nr_segments;
 	uint16_t rqid;
+	uint16_t ref_rqid;
 
 	unsigned int nr_grants;		/* number of grants in gref[] */
 	struct scsiif_request_segment *sg;	/* scatter/gather elements */
+	struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
 
 	/* Do reset or abort function. */
 	wait_queue_head_t wq_reset;	/* reset work queue           */
@@ -172,68 +175,90 @@ static void scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
 		scsifront_wake_up(info);
 }
 
-static struct vscsiif_request *scsifront_pre_req(struct vscsifrnt_info *info)
+static int scsifront_do_request(struct vscsifrnt_info *info,
+				struct vscsifrnt_shadow *shadow)
 {
 	struct vscsiif_front_ring *ring = &(info->ring);
 	struct vscsiif_request *ring_req;
+	struct scsi_cmnd *sc = shadow->sc;
 	uint32_t id;
+	int i, notify;
+
+	if (RING_FULL(&info->ring))
+		return -EBUSY;
 
 	id = scsifront_get_rqid(info);	/* use id in response */
 	if (id >= VSCSIIF_MAX_REQS)
-		return NULL;
+		return -EBUSY;
 
-	ring_req = RING_GET_REQUEST(&(info->ring), ring->req_prod_pvt);
+	info->shadow[id] = shadow;
+	shadow->rqid = id;
 
+	ring_req = RING_GET_REQUEST(&(info->ring), ring->req_prod_pvt);
 	ring->req_prod_pvt++;
 
-	ring_req->rqid = (uint16_t)id;
+	ring_req->rqid        = id;
+	ring_req->act         = shadow->act;
+	ring_req->ref_rqid    = shadow->ref_rqid;
+	ring_req->nr_segments = shadow->nr_segments;
 
-	return ring_req;
-}
+	ring_req->id      = sc->device->id;
+	ring_req->lun     = sc->device->lun;
+	ring_req->channel = sc->device->channel;
+	ring_req->cmd_len = sc->cmd_len;
 
-static void scsifront_do_request(struct vscsifrnt_info *info)
-{
-	struct vscsiif_front_ring *ring = &(info->ring);
-	int notify;
+	BUG_ON(sc->cmd_len > VSCSIIF_MAX_COMMAND_SIZE);
+
+	memcpy(ring_req->cmnd, sc->cmnd, sc->cmd_len);
+
+	ring_req->sc_data_direction   = (uint8_t)sc->sc_data_direction;
+	ring_req->timeout_per_command = sc->request->timeout / HZ;
+
+	for (i = 0; i < (shadow->nr_segments & ~VSCSIIF_SG_GRANT); i++)
+		ring_req->seg[i] = shadow->seg[i];
 
 	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(ring, notify);
 	if (notify)
 		notify_remote_via_irq(info->irq);
+
+	return 0;
 }
 
-static void scsifront_gnttab_done(struct vscsifrnt_info *info, uint32_t id)
+static void scsifront_gnttab_done(struct vscsifrnt_info *info,
+				  struct vscsifrnt_shadow *shadow)
 {
-	struct vscsifrnt_shadow *s = info->shadow[id];
 	int i;
 
-	if (s->sc->sc_data_direction == DMA_NONE)
+	if (shadow->sc->sc_data_direction == DMA_NONE)
 		return;
 
-	for (i = 0; i < s->nr_grants; i++) {
-		if (unlikely(gnttab_query_foreign_access(s->gref[i]) != 0)) {
+	for (i = 0; i < shadow->nr_grants; i++) {
+		if (unlikely(gnttab_query_foreign_access(shadow->gref[i]))) {
 			shost_printk(KERN_ALERT, info->host, KBUILD_MODNAME
 				     "grant still in use by backend\n");
 			BUG();
 		}
-		gnttab_end_foreign_access(s->gref[i], 0, 0UL);
+		gnttab_end_foreign_access(shadow->gref[i], 0, 0UL);
 	}
 
-	kfree(s->sg);
+	kfree(shadow->sg);
 }
 
 static void scsifront_cdb_cmd_done(struct vscsifrnt_info *info,
 				   struct vscsiif_response *ring_rsp)
 {
+	struct vscsifrnt_shadow *shadow;
 	struct scsi_cmnd *sc;
 	uint32_t id;
 	uint8_t sense_len;
 
 	id = ring_rsp->rqid;
-	sc = info->shadow[id]->sc;
+	shadow = info->shadow[id];
+	sc = shadow->sc;
 
 	BUG_ON(sc == NULL);
 
-	scsifront_gnttab_done(info, id);
+	scsifront_gnttab_done(info, shadow);
 	scsifront_put_rqid(info, id);
 
 	sc->result = ring_rsp->rslt;
@@ -366,7 +391,6 @@ static void scsifront_finish_all(struct vscsifrnt_info *info)
 
 static int map_data_for_request(struct vscsifrnt_info *info,
 				struct scsi_cmnd *sc,
-				struct vscsiif_request *ring_req,
 				struct vscsifrnt_shadow *shadow)
 {
 	grant_ref_t gref_head;
@@ -379,7 +403,6 @@ static int map_data_for_request(struct vscsifrnt_info *info,
 	struct scatterlist *sg;
 	struct scsiif_request_segment *seg;
 
-	ring_req->nr_segments = 0;
 	if (sc->sc_data_direction == DMA_NONE || !data_len)
 		return 0;
 
@@ -398,7 +421,7 @@ static int map_data_for_request(struct vscsifrnt_info *info,
 		if (!shadow->sg)
 			return -ENOMEM;
 	}
-	seg = shadow->sg ? : ring_req->seg;
+	seg = shadow->sg ? : shadow->seg;
 
 	err = gnttab_alloc_grant_references(seg_grants + data_grants,
 					    &gref_head);
@@ -423,9 +446,9 @@ static int map_data_for_request(struct vscsifrnt_info *info,
 				info->dev->otherend_id,
 				xen_page_to_gfn(page), 1);
 			shadow->gref[ref_cnt] = ref;
-			ring_req->seg[ref_cnt].gref   = ref;
-			ring_req->seg[ref_cnt].offset = (uint16_t)off;
-			ring_req->seg[ref_cnt].length = (uint16_t)bytes;
+			shadow->seg[ref_cnt].gref   = ref;
+			shadow->seg[ref_cnt].offset = (uint16_t)off;
+			shadow->seg[ref_cnt].length = (uint16_t)bytes;
 
 			page++;
 			len -= bytes;
@@ -473,44 +496,14 @@ static int map_data_for_request(struct vscsifrnt_info *info,
 	}
 
 	if (seg_grants)
-		ring_req->nr_segments = VSCSIIF_SG_GRANT | seg_grants;
+		shadow->nr_segments = VSCSIIF_SG_GRANT | seg_grants;
 	else
-		ring_req->nr_segments = (uint8_t)ref_cnt;
+		shadow->nr_segments = (uint8_t)ref_cnt;
 	shadow->nr_grants = ref_cnt;
 
 	return 0;
 }
 
-static struct vscsiif_request *scsifront_command2ring(
-		struct vscsifrnt_info *info, struct scsi_cmnd *sc,
-		struct vscsifrnt_shadow *shadow)
-{
-	struct vscsiif_request *ring_req;
-
-	memset(shadow, 0, sizeof(*shadow));
-
-	ring_req = scsifront_pre_req(info);
-	if (!ring_req)
-		return NULL;
-
-	info->shadow[ring_req->rqid] = shadow;
-	shadow->rqid = ring_req->rqid;
-
-	ring_req->id      = sc->device->id;
-	ring_req->lun     = sc->device->lun;
-	ring_req->channel = sc->device->channel;
-	ring_req->cmd_len = sc->cmd_len;
-
-	BUG_ON(sc->cmd_len > VSCSIIF_MAX_COMMAND_SIZE);
-
-	memcpy(ring_req->cmnd, sc->cmnd, sc->cmd_len);
-
-	ring_req->sc_data_direction   = (uint8_t)sc->sc_data_direction;
-	ring_req->timeout_per_command = sc->request->timeout / HZ;
-
-	return ring_req;
-}
-
 static int scsifront_enter(struct vscsifrnt_info *info)
 {
 	if (info->pause)
@@ -536,36 +529,25 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
 				  struct scsi_cmnd *sc)
 {
 	struct vscsifrnt_info *info = shost_priv(shost);
-	struct vscsiif_request *ring_req;
 	struct vscsifrnt_shadow *shadow = scsi_cmd_priv(sc);
 	unsigned long flags;
 	int err;
-	uint16_t rqid;
+
+	sc->result = 0;
+	memset(shadow, 0, sizeof(*shadow));
+
+	shadow->sc  = sc;
+	shadow->act = VSCSIIF_ACT_SCSI_CDB;
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	if (scsifront_enter(info)) {
 		spin_unlock_irqrestore(shost->host_lock, flags);
 		return SCSI_MLQUEUE_HOST_BUSY;
 	}
-	if (RING_FULL(&info->ring))
-		goto busy;
-
-	ring_req = scsifront_command2ring(info, sc, shadow);
-	if (!ring_req)
-		goto busy;
-
-	sc->result = 0;
-
-	rqid = ring_req->rqid;
-	ring_req->act = VSCSIIF_ACT_SCSI_CDB;
 
-	shadow->sc  = sc;
-	shadow->act = VSCSIIF_ACT_SCSI_CDB;
-
-	err = map_data_for_request(info, sc, ring_req, shadow);
+	err = map_data_for_request(info, sc, shadow);
 	if (err < 0) {
 		pr_debug("%s: err %d\n", __func__, err);
-		scsifront_put_rqid(info, rqid);
 		scsifront_return(info);
 		spin_unlock_irqrestore(shost->host_lock, flags);
 		if (err == -ENOMEM)
@@ -575,7 +557,11 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
 		return 0;
 	}
 
-	scsifront_do_request(info);
+	if (scsifront_do_request(info, shadow)) {
+		scsifront_gnttab_done(info, shadow);
+		goto busy;
+	}
+
 	scsifront_return(info);
 	spin_unlock_irqrestore(shost->host_lock, flags);
 
@@ -598,26 +584,30 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
 	struct Scsi_Host *host = sc->device->host;
 	struct vscsifrnt_info *info = shost_priv(host);
 	struct vscsifrnt_shadow *shadow, *s = scsi_cmd_priv(sc);
-	struct vscsiif_request *ring_req;
 	int err = 0;
 
-	shadow = kmalloc(sizeof(*shadow), GFP_NOIO);
+	shadow = kzalloc(sizeof(*shadow), GFP_NOIO);
 	if (!shadow)
 		return FAILED;
 
+	shadow->act = act;
+	shadow->rslt_reset = RSLT_RESET_WAITING;
+	shadow->sc = sc;
+	shadow->ref_rqid = s->rqid;
+	init_waitqueue_head(&shadow->wq_reset);
+
 	spin_lock_irq(host->host_lock);
 
 	for (;;) {
-		if (!RING_FULL(&info->ring)) {
-			ring_req = scsifront_command2ring(info, sc, shadow);
-			if (ring_req)
-				break;
-		}
-		if (err || info->pause) {
-			spin_unlock_irq(host->host_lock);
-			kfree(shadow);
-			return FAILED;
-		}
+		if (scsifront_enter(info))
+			goto fail;
+
+		if (!scsifront_do_request(info, shadow))
+			break;
+
+		scsifront_return(info);
+		if (err)
+			goto fail;
 		info->wait_ring_available = 1;
 		spin_unlock_irq(host->host_lock);
 		err = wait_event_interruptible(info->wq_sync,
@@ -625,22 +615,6 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
 		spin_lock_irq(host->host_lock);
 	}
 
-	if (scsifront_enter(info)) {
-		spin_unlock_irq(host->host_lock);
-		return FAILED;
-	}
-
-	ring_req->act = act;
-	ring_req->ref_rqid = s->rqid;
-
-	shadow->act = act;
-	shadow->rslt_reset = RSLT_RESET_WAITING;
-	init_waitqueue_head(&shadow->wq_reset);
-
-	ring_req->nr_segments = 0;
-
-	scsifront_do_request(info);
-
 	spin_unlock_irq(host->host_lock);
 	err = wait_event_interruptible(shadow->wq_reset, shadow->wait_reset);
 	spin_lock_irq(host->host_lock);
@@ -659,6 +633,11 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
 	scsifront_return(info);
 	spin_unlock_irq(host->host_lock);
 	return err;
+
+fail:
+	spin_unlock_irq(host->host_lock);
+	kfree(shadow);
+	return FAILED;
 }
 
 static int scsifront_eh_abort_handler(struct scsi_cmnd *sc)
@@ -1060,13 +1039,9 @@ static void scsifront_read_backend_params(struct xenbus_device *dev,
 					  struct vscsifrnt_info *info)
 {
 	unsigned int sg_grant, nr_segs;
-	int ret;
 	struct Scsi_Host *host = info->host;
 
-	ret = xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg-grant", "%u",
-			   &sg_grant);
-	if (ret != 1)
-		sg_grant = 0;
+	sg_grant = xenbus_read_unsigned(dev->otherend, "feature-sg-grant", 0);
 	nr_segs = min_t(unsigned int, sg_grant, SG_ALL);
 	nr_segs = max_t(unsigned int, nr_segs, VSCSIIF_SG_TABLESIZE);
 	nr_segs = min_t(unsigned int, nr_segs,
diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c
index 0567d517eed3..d0115a7af0a9 100644
--- a/drivers/video/fbdev/xen-fbfront.c
+++ b/drivers/video/fbdev/xen-fbfront.c
@@ -633,7 +633,6 @@ static void xenfb_backend_changed(struct xenbus_device *dev,
 				  enum xenbus_state backend_state)
 {
 	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
-	int val;
 
 	switch (backend_state) {
 	case XenbusStateInitialising:
@@ -657,16 +656,12 @@ InitWait:
 		if (dev->state != XenbusStateConnected)
 			goto InitWait; /* no InitWait seen yet, fudge it */
 
-		if (xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-				 "request-update", "%d", &val) < 0)
-			val = 0;
-		if (val)
+		if (xenbus_read_unsigned(info->xbdev->otherend,
+					 "request-update", 0))
 			info->update_wanted = 1;
 
-		if (xenbus_scanf(XBT_NIL, dev->otherend,
-				 "feature-resize", "%d", &val) < 0)
-			val = 0;
-		info->feature_resize = val;
+		info->feature_resize = xenbus_read_unsigned(dev->otherend,
+							"feature-resize", 0);
 		break;
 
 	case XenbusStateClosed:
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index e4db19e88ab1..db107fa50ca1 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -180,7 +180,6 @@ static void __balloon_append(struct page *page)
 static void balloon_append(struct page *page)
 {
 	__balloon_append(page);
-	adjust_managed_page_count(page, -1);
 }
 
 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
@@ -201,8 +200,6 @@ static struct page *balloon_retrieve(bool require_lowmem)
 	else
 		balloon_stats.balloon_low--;
 
-	adjust_managed_page_count(page, 1);
-
 	return page;
 }
 
@@ -478,7 +475,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 #endif
 
 		/* Relinquish the page back to the allocator. */
-		__free_reserved_page(page);
+		free_reserved_page(page);
 	}
 
 	balloon_stats.current_pages += rc;
@@ -509,6 +506,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 			state = BP_EAGAIN;
 			break;
 		}
+		adjust_managed_page_count(page, -1);
 		scrub_page(page);
 		list_add(&page->lru, &pages);
 	}
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index adc19ce3cc66..fd8e872d2943 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -947,7 +947,7 @@ static int find_virq(unsigned int virq, unsigned int cpu)
 			continue;
 		if (status.status != EVTCHNSTAT_virq)
 			continue;
-		if (status.u.virq == virq && status.vcpu == cpu) {
+		if (status.u.virq == virq && status.vcpu == xen_vcpu_nr(cpu)) {
 			rc = port;
 			break;
 		}
diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index 7a47c4c9fb1b..1bf55a32a4b3 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -127,18 +127,21 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
 	struct gntalloc_gref *gref, *next;
 
 	readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
-	rc = -ENOMEM;
 	for (i = 0; i < op->count; i++) {
 		gref = kzalloc(sizeof(*gref), GFP_KERNEL);
-		if (!gref)
+		if (!gref) {
+			rc = -ENOMEM;
 			goto undo;
+		}
 		list_add_tail(&gref->next_gref, &queue_gref);
 		list_add_tail(&gref->next_file, &queue_file);
 		gref->users = 1;
 		gref->file_index = op->index + i * PAGE_SIZE;
 		gref->page = alloc_page(GFP_KERNEL|__GFP_ZERO);
-		if (!gref->page)
+		if (!gref->page) {
+			rc = -ENOMEM;
 			goto undo;
+		}
 
 		/* Grant foreign access to the page. */
 		rc = gnttab_grant_foreign_access(op->domid,
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index bb952121ea94..2ef2b61b69df 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1007,7 +1007,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 
 	vma->vm_ops = &gntdev_vmops;
 
-	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
+	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP;
 
 	if (use_ptemod)
 		vma->vm_flags |= VM_DONTCOPY;
diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
index b59c9455aae1..112ce422dc22 100644
--- a/drivers/xen/platform-pci.c
+++ b/drivers/xen/platform-pci.c
@@ -125,8 +125,4 @@ static struct pci_driver platform_driver = {
 	.id_table =       platform_pci_tbl,
 };
 
-static int __init platform_pci_init(void)
-{
-	return pci_register_driver(&platform_driver);
-}
-device_initcall(platform_pci_init);
+builtin_pci_driver(platform_driver);
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index 5ce878c51d03..3f0aee0a068b 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -362,7 +362,7 @@ static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev)
 	int err = 0;
 	int num_devs;
 	int domain, bus, slot, func;
-	int substate;
+	unsigned int substate;
 	int i, len;
 	char state_str[64];
 	char dev_str[64];
@@ -395,10 +395,8 @@ static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev)
 					 "configuration");
 			goto out;
 		}
-		err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, state_str,
-				   "%d", &substate);
-		if (err != 1)
-			substate = XenbusStateUnknown;
+		substate = xenbus_read_unsigned(pdev->xdev->nodename, state_str,
+						XenbusStateUnknown);
 
 		switch (substate) {
 		case XenbusStateInitialising:
diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index 1e8be12ebb55..6c0ead4be784 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -538,6 +538,8 @@ static int xenbus_file_open(struct inode *inode, struct file *filp)
 
 	nonseekable_open(inode, filp);
 
+	filp->f_mode &= ~FMODE_ATOMIC_POS; /* cdev-style semantics */
+
 	u = kzalloc(sizeof(*u), GFP_KERNEL);
 	if (u == NULL)
 		return -ENOMEM;
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 33a31cfef55d..4bdf654041e9 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -702,7 +702,7 @@ device_initcall(xenbus_probe_initcall);
  */
 static int __init xenstored_local_init(void)
 {
-	int err = 0;
+	int err = -ENOMEM;
 	unsigned long page = 0;
 	struct evtchn_alloc_unbound alloc_unbound;
 
@@ -826,7 +826,7 @@ static int __init xenbus_init(void)
 	 * Create xenfs mountpoint in /proc for compatibility with
 	 * utilities that expect to find "xenbus" under "/proc/xen".
 	 */
-	proc_mkdir("xen", NULL);
+	proc_create_mount_point("xen");
 #endif
 
 out_error:
diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c
index 04f7f85a5edf..37929df829a3 100644
--- a/drivers/xen/xenbus/xenbus_probe_backend.c
+++ b/drivers/xen/xenbus/xenbus_probe_backend.c
@@ -224,13 +224,7 @@ static int read_frontend_details(struct xenbus_device *xendev)
 
 int xenbus_dev_is_online(struct xenbus_device *dev)
 {
-	int rc, val;
-
-	rc = xenbus_scanf(XBT_NIL, dev->nodename, "online", "%d", &val);
-	if (rc != 1)
-		val = 0; /* no online node present */
-
-	return val;
+	return !!xenbus_read_unsigned(dev->nodename, "online", 0);
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_is_online);
 
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 22f7cd711c57..6afb993c5809 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -559,6 +559,21 @@ int xenbus_scanf(struct xenbus_transaction t,
 }
 EXPORT_SYMBOL_GPL(xenbus_scanf);
 
+/* Read an (optional) unsigned value. */
+unsigned int xenbus_read_unsigned(const char *dir, const char *node,
+				  unsigned int default_val)
+{
+	unsigned int val;
+	int ret;
+
+	ret = xenbus_scanf(XBT_NIL, dir, node, "%u", &val);
+	if (ret <= 0)
+		val = default_val;
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(xenbus_read_unsigned);
+
 /* Single printf and write: returns -errno or 0. */
 int xenbus_printf(struct xenbus_transaction t,
 		  const char *dir, const char *node, const char *fmt, ...)
@@ -672,7 +687,7 @@ static bool xen_strict_xenbus_quirk(void)
 }
 static void xs_reset_watches(void)
 {
-	int err, supported = 0;
+	int err;
 
 	if (!xen_hvm_domain() || xen_initial_domain())
 		return;
@@ -680,9 +695,8 @@ static void xs_reset_watches(void)
 	if (xen_strict_xenbus_quirk())
 		return;
 
-	err = xenbus_scanf(XBT_NIL, "control",
-			"platform-feature-xs_reset_watches", "%d", &supported);
-	if (err != 1 || !supported)
+	if (!xenbus_read_unsigned("control",
+				  "platform-feature-xs_reset_watches", 0))
 		return;
 
 	err = xs_error(xs_single(XBT_NIL, XS_RESET_WATCHES, "", NULL));