[PATCH v6 1/3] xenbus_client: Extend interface to support multi-page ring

[PATCH v6 1/3] xenbus_client: Extend interface to support multi-page ring

[Bob Liu]

From: Wei Liu <wei.liu2@citrix.com>

Originally Xen PV drivers only use single-page ring to pass along
information. This might limit the throughput between frontend and
backend.

The patch extends Xenbus driver to support multi-page ring, which in
general should improve throughput if ring is the bottleneck. Changes to
various frontend / backend to adapt to the new interface are also
included.

Affected Xen drivers:
* blkfront/back
* netfront/back
* pcifront/back
* scsifront/back

The interface is documented, as before, in xenbus_client.c.

Change in V2:
* allow ring has arbitrary number of pages <= XENBUS_MAX_RING_PAGES

Change in V3:
* update function prototypes
* carefully deal with types of different sizes

Change in V4:
* use PAGE_KERNEL instead of PAGE_KERNEL_IO to avoid breakage on Arm

Change in V5:
* fix off-by-one error and other minor glitches spotted by Mathew Daley

Change in V6:
* add pvscsi driver support by Bob Liu

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 drivers/block/xen-blkback/xenbus.c |    5 +-
 drivers/block/xen-blkfront.c       |    5 +-
 drivers/net/xen-netback/netback.c  |    4 +-
 drivers/net/xen-netfront.c         |    9 +-
 drivers/pci/xen-pcifront.c         |    5 +-
 drivers/scsi/xen-scsifront.c       |    5 +-
 drivers/xen/xen-pciback/xenbus.c   |    2 +-
 drivers/xen/xen-scsiback.c         |    2 +-
 drivers/xen/xenbus/xenbus_client.c |  387 ++++++++++++++++++++++++++----------
 include/xen/xenbus.h               |   20 +-
 10 files changed, 321 insertions(+), 123 deletions(-)

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index e3afe97..ff30259 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -193,7 +193,7 @@ fail:
 	return ERR_PTR(-ENOMEM);
 }
 
-static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
+static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
 			 unsigned int evtchn)
 {
 	int err;
@@ -202,7 +202,8 @@ static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 	if (blkif->irq)
 		return 0;
 
-	err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
+	err = xenbus_map_ring_valloc(blkif->be->dev, &gref, 1,
+				     &blkif->blk_ring);
 	if (err < 0)
 		return err;
 
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 37779e4..2c61cf8 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1245,6 +1245,7 @@ static int setup_blkring(struct xenbus_device *dev,
 			 struct blkfront_info *info)
 {
 	struct blkif_sring *sring;
+	grant_ref_t gref;
 	int err;
 
 	info->ring_ref = GRANT_INVALID_REF;
@@ -1257,13 +1258,13 @@ static int setup_blkring(struct xenbus_device *dev,
 	SHARED_RING_INIT(sring);
 	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
+	err = xenbus_grant_ring(dev, info->ring.sring, 1, &gref);
 	if (err < 0) {
 		free_page((unsigned long)sring);
 		info->ring.sring = NULL;
 		goto fail;
 	}
-	info->ring_ref = err;
+	info->ring_ref = gref;
 
 	err = xenbus_alloc_evtchn(dev, &info->evtchn);
 	if (err)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 997cf09..865203f 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1782,7 +1782,7 @@ int xenvif_map_frontend_rings(struct xenvif_queue *queue,
 	int err = -ENOMEM;
 
 	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
-				     tx_ring_ref, &addr);
+				     &tx_ring_ref, 1, &addr);
 	if (err)
 		goto err;
 
@@ -1790,7 +1790,7 @@ int xenvif_map_frontend_rings(struct xenvif_queue *queue,
 	BACK_RING_INIT(&queue->tx, txs, PAGE_SIZE);
 
 	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
-				     rx_ring_ref, &addr);
+				     &rx_ring_ref, 1, &addr);
 	if (err)
 		goto err;
 
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index e9b960f..13f5e7f 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1486,6 +1486,7 @@ static int setup_netfront(struct xenbus_device *dev,
 {
 	struct xen_netif_tx_sring *txs;
 	struct xen_netif_rx_sring *rxs;
+	grant_ref_t gref;
 	int err;
 
 	queue->tx_ring_ref = GRANT_INVALID_REF;
@@ -1502,10 +1503,10 @@ static int setup_netfront(struct xenbus_device *dev,
 	SHARED_RING_INIT(txs);
 	FRONT_RING_INIT(&queue->tx, txs, PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, virt_to_mfn(txs));
+	err = xenbus_grant_ring(dev, txs, 1, &gref);
 	if (err < 0)
 		goto grant_tx_ring_fail;
-	queue->tx_ring_ref = err;
+	queue->tx_ring_ref = gref;
 
 	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
 	if (!rxs) {
@@ -1516,10 +1517,10 @@ static int setup_netfront(struct xenbus_device *dev,
 	SHARED_RING_INIT(rxs);
 	FRONT_RING_INIT(&queue->rx, rxs, PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, virt_to_mfn(rxs));
+	err = xenbus_grant_ring(dev, rxs, 1, &gref);
 	if (err < 0)
 		goto grant_rx_ring_fail;
-	queue->rx_ring_ref = err;
+	queue->rx_ring_ref = gref;
 
 	if (feature_split_evtchn)
 		err = setup_netfront_split(queue);
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index b1ffebe..7cfd2db 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -777,12 +777,13 @@ static int pcifront_publish_info(struct pcifront_device *pdev)
 {
 	int err = 0;
 	struct xenbus_transaction trans;
+	grant_ref_t gref;
 
-	err = xenbus_grant_ring(pdev->xdev, virt_to_mfn(pdev->sh_info));
+	err = xenbus_grant_ring(pdev->xdev, pdev->sh_info, 1, &gref);
 	if (err < 0)
 		goto out;
 
-	pdev->gnt_ref = err;
+	pdev->gnt_ref = gref;
 
 	err = xenbus_alloc_evtchn(pdev->xdev, &pdev->evtchn);
 	if (err)
diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
index 34199d2..2e9de74 100644
--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -644,6 +644,7 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
 {
 	struct xenbus_device *dev = info->dev;
 	struct vscsiif_sring *sring;
+	grant_ref_t gref;
 	int err = -ENOMEM;
 
 	/***** Frontend to Backend ring start *****/
@@ -656,14 +657,14 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
 	SHARED_RING_INIT(sring);
 	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, virt_to_mfn(sring));
+	err = xenbus_grant_ring(dev, sring, 1, &gref);
 	if (err < 0) {
 		free_page((unsigned long)sring);
 		xenbus_dev_fatal(dev, err,
 			"fail to grant shared ring (Front to Back)");
 		return err;
 	}
-	info->ring_ref = err;
+	info->ring_ref = gref;
 
 	err = xenbus_alloc_evtchn(dev, &info->evtchn);
 	if (err) {
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index fe17c80..98bc345 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -113,7 +113,7 @@ static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref,
 		"Attaching to frontend resources - gnt_ref=%d evtchn=%d\n",
 		gnt_ref, remote_evtchn);
 
-	err = xenbus_map_ring_valloc(pdev->xdev, gnt_ref, &vaddr);
+	err = xenbus_map_ring_valloc(pdev->xdev, &gnt_ref, 1, &vaddr);
 	if (err < 0) {
 		xenbus_dev_fatal(pdev->xdev, err,
 				"Error mapping other domain page in ours.");
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 42bd55a..6cc753d 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -810,7 +810,7 @@ static int scsiback_init_sring(struct vscsibk_info *info, grant_ref_t ring_ref,
 	if (info->irq)
 		return -1;
 
-	err = xenbus_map_ring_valloc(info->dev, ring_ref, &area);
+	err = xenbus_map_ring_valloc(info->dev, &ring_ref, 1, &area);
 	if (err)
 		return err;
 
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index ca74410..96b2011 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -52,17 +52,25 @@
 struct xenbus_map_node {
 	struct list_head next;
 	union {
-		struct vm_struct *area; /* PV */
-		struct page *page;     /* HVM */
+		struct {
+			struct vm_struct *area;
+		} pv;
+		struct {
+			struct page *pages[XENBUS_MAX_RING_PAGES];
+			void *addr;
+		} hvm;
 	};
-	grant_handle_t handle;
+	grant_handle_t handles[XENBUS_MAX_RING_PAGES];
+	unsigned int   nr_handles;
 };
 
 static DEFINE_SPINLOCK(xenbus_valloc_lock);
 static LIST_HEAD(xenbus_valloc_pages);
 
 struct xenbus_ring_ops {
-	int (*map)(struct xenbus_device *dev, int gnt, void **vaddr);
+	int (*map)(struct xenbus_device *dev,
+		   grant_ref_t *gnt_refs, unsigned int nr_grefs,
+		   void **vaddr);
 	int (*unmap)(struct xenbus_device *dev, void *vaddr);
 };
 
@@ -355,17 +363,39 @@ static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
 /**
  * xenbus_grant_ring
  * @dev: xenbus device
- * @ring_mfn: mfn of ring to grant
-
- * Grant access to the given @ring_mfn to the peer of the given device.  Return
- * a grant reference on success, or -errno on error. On error, the device will
- * switch to XenbusStateClosing, and the error will be saved in the store.
+ * @vaddr: starting virtual address of the ring
+ * @nr_pages: number of pages to be granted
+ * @grefs: grant reference array to be filled in
+ *
+ * Grant access to the given @vaddr to the peer of the given device.
+ * Then fill in @grefs with grant references.  Return 0 on success, or
+ * -errno on error.  On error, the device will switch to
+ * XenbusStateClosing, and the error will be saved in the store.
  */
-int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn)
+int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
+		      unsigned int nr_pages, grant_ref_t *grefs)
 {
-	int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0);
-	if (err < 0)
-		xenbus_dev_fatal(dev, err, "granting access to ring page");
+	int err;
+	int i, j;
+
+	for (i = 0; i < nr_pages; i++) {
+		unsigned long addr = (unsigned long)vaddr +
+			(PAGE_SIZE * i);
+		err = gnttab_grant_foreign_access(dev->otherend_id,
+						  virt_to_mfn(addr), 0);
+		if (err < 0) {
+			xenbus_dev_fatal(dev, err,
+					 "granting access to ring page");
+			goto fail;
+		}
+		grefs[i] = err;
+	}
+
+	return 0;
+
+fail:
+	for (j = 0; j < i; j++)
+		gnttab_end_foreign_access_ref(grefs[j], 0);
 	return err;
 }
 EXPORT_SYMBOL_GPL(xenbus_grant_ring);
@@ -419,62 +449,130 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
 /**
  * xenbus_map_ring_valloc
  * @dev: xenbus device
- * @gnt_ref: grant reference
+ * @gnt_refs: grant reference array
+ * @nr_grefs: number of grant references
  * @vaddr: pointer to address to be filled out by mapping
  *
- * Based on Rusty Russell's skeleton driver's map_page.
- * Map a page of memory into this domain from another domain's grant table.
- * xenbus_map_ring_valloc allocates a page of virtual address space, maps the
- * page to that address, and sets *vaddr to that address.
- * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
- * or -ENOMEM on error. If an error is returned, device will switch to
+ * Map @nr_grefs pages of memory into this domain from another
+ * domain's grant table.  xenbus_map_ring_valloc allocates @nr_grefs
+ * pages of virtual address space, maps the pages to that address, and
+ * sets *vaddr to that address.  Returns 0 on success, and GNTST_*
+ * (see xen/include/interface/grant_table.h) or -ENOMEM / -EINVAL on
+ * error. If an error is returned, device will switch to
  * XenbusStateClosing and the error message will be saved in XenStore.
  */
-int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
+int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
+			   unsigned int nr_grefs, void **vaddr)
 {
-	return ring_ops->map(dev, gnt_ref, vaddr);
+	return ring_ops->map(dev, gnt_refs, nr_grefs, vaddr);
 }
 EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
 
+/* N.B. sizeof(phys_addr_t) doesn't always equal to sizeof(unsigned
+ * long), e.g. 32-on-64.  Caller is responsible for preparing the
+ * right array to feed into this function */
+static int __xenbus_map_ring(struct xenbus_device *dev,
+			     grant_ref_t *gnt_refs,
+			     unsigned int nr_grefs,
+			     grant_handle_t *handles,
+			     phys_addr_t *addrs,
+			     unsigned int flags,
+			     bool *leaked)
+{
+	struct gnttab_map_grant_ref map[XENBUS_MAX_RING_PAGES];
+	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_PAGES];
+	int i, j;
+	int err = GNTST_okay;
+
+	if (nr_grefs > XENBUS_MAX_RING_PAGES)
+		return -EINVAL;
+
+	for (i = 0; i < nr_grefs; i++) {
+		memset(&map[i], 0, sizeof(map[i]));
+		gnttab_set_map_op(&map[i], addrs[i], flags, gnt_refs[i],
+				  dev->otherend_id);
+		handles[i] = INVALID_GRANT_HANDLE;
+	}
+
+	gnttab_batch_map(map, i);
+
+	for (i = 0; i < nr_grefs; i++) {
+		if (map[i].status != GNTST_okay) {
+			err = map[i].status;
+			xenbus_dev_fatal(dev, map[i].status,
+					 "mapping in shared page %d from domain %d",
+					 gnt_refs[i], dev->otherend_id);
+			goto fail;
+		} else
+			handles[i] = map[i].handle;
+	}
+
+	return GNTST_okay;
+
+ fail:
+	for (i = j = 0; i < nr_grefs; i++) {
+		if (handles[i] != INVALID_GRANT_HANDLE) {
+			memset(&unmap[j], 0, sizeof(unmap[j]));
+			gnttab_set_unmap_op(&unmap[j], (phys_addr_t)addrs[i],
+					    GNTMAP_host_map, handles[i]);
+			j++;
+		}
+	}
+
+	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, j))
+		BUG();
+
+	*leaked = false;
+	for (i = 0; i < j; i++) {
+		if (unmap[i].status != GNTST_okay) {
+			*leaked = true;
+			break;
+		}
+	}
+
+	return err;
+}
+
 static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
-				     int gnt_ref, void **vaddr)
+				     grant_ref_t *gnt_refs,
+				     unsigned int nr_grefs,
+				     void **vaddr)
 {
-	struct gnttab_map_grant_ref op = {
-		.flags = GNTMAP_host_map | GNTMAP_contains_pte,
-		.ref   = gnt_ref,
-		.dom   = dev->otherend_id,
-	};
 	struct xenbus_map_node *node;
 	struct vm_struct *area;
-	pte_t *pte;
+	pte_t *ptes[XENBUS_MAX_RING_PAGES];
+	phys_addr_t phys_addrs[XENBUS_MAX_RING_PAGES];
+	int err = GNTST_okay;
+	int i;
+	bool leaked;
 
 	*vaddr = NULL;
 
+	if (nr_grefs > XENBUS_MAX_RING_PAGES)
+		return -EINVAL;
+
 	node = kzalloc(sizeof(*node), GFP_KERNEL);
 	if (!node)
 		return -ENOMEM;
 
-	area = alloc_vm_area(PAGE_SIZE, &pte);
+	area = alloc_vm_area(PAGE_SIZE * nr_grefs, ptes);
 	if (!area) {
 		kfree(node);
 		return -ENOMEM;
 	}
 
-	op.host_addr = arbitrary_virt_to_machine(pte).maddr;
+	for (i = 0; i < nr_grefs; i++)
+		phys_addrs[i] = arbitrary_virt_to_machine(ptes[i]).maddr;
 
-	gnttab_batch_map(&op, 1);
-
-	if (op.status != GNTST_okay) {
-		free_vm_area(area);
-		kfree(node);
-		xenbus_dev_fatal(dev, op.status,
-				 "mapping in shared page %d from domain %d",
-				 gnt_ref, dev->otherend_id);
-		return op.status;
-	}
+	err = __xenbus_map_ring(dev, gnt_refs, nr_grefs, node->handles,
+				phys_addrs,
+				GNTMAP_host_map | GNTMAP_contains_pte,
+				&leaked);
+	if (err)
+		goto failed;
 
-	node->handle = op.handle;
-	node->area = area;
+	node->nr_handles = nr_grefs;
+	node->pv.area = area;
 
 	spin_lock(&xenbus_valloc_lock);
 	list_add(&node->next, &xenbus_valloc_pages);
@@ -482,14 +580,33 @@ static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
 
 	*vaddr = area->addr;
 	return 0;
+
+failed:
+	if (!leaked)
+		free_vm_area(area);
+	else
+		pr_alert("leaking VM area %p size %u page(s)", area, nr_grefs);
+
+	kfree(node);
+	return err;
 }
 
 static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
-				      int gnt_ref, void **vaddr)
+				      grant_ref_t *gnt_ref,
+				      unsigned int nr_grefs,
+				      void **vaddr)
 {
 	struct xenbus_map_node *node;
+	int i;
 	int err;
 	void *addr;
+	bool leaked = false;
+	/* Why do we need two arrays? See comment of __xenbus_map_ring */
+	phys_addr_t phys_addrs[XENBUS_MAX_RING_PAGES];
+	unsigned long addrs[XENBUS_MAX_RING_PAGES];
+
+	if (nr_grefs > XENBUS_MAX_RING_PAGES)
+		return -EINVAL;
 
 	*vaddr = NULL;
 
@@ -497,15 +614,32 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
 	if (!node)
 		return -ENOMEM;
 
-	err = alloc_xenballooned_pages(1, &node->page, false /* lowmem */);
+	err = alloc_xenballooned_pages(nr_grefs, node->hvm.pages,
+				       false /* lowmem */);
 	if (err)
 		goto out_err;
 
-	addr = pfn_to_kaddr(page_to_pfn(node->page));
+	for (i = 0; i < nr_grefs; i++) {
+		unsigned long pfn = page_to_pfn(node->hvm.pages[i]);
+		phys_addrs[i] = (unsigned long)pfn_to_kaddr(pfn);
+		addrs[i] = (unsigned long)pfn_to_kaddr(pfn);
+	}
+
+	err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
+				phys_addrs, GNTMAP_host_map, &leaked);
+	node->nr_handles = nr_grefs;
 
-	err = xenbus_map_ring(dev, gnt_ref, &node->handle, addr);
 	if (err)
-		goto out_err_free_ballooned_pages;
+		goto out_free_ballooned_pages;
+
+	addr = vmap(node->hvm.pages, nr_grefs, VM_MAP | VM_IOREMAP,
+		    PAGE_KERNEL);
+	if (!addr) {
+		err = -ENOMEM;
+		goto out_xenbus_unmap_ring;
+	}
+
+	node->hvm.addr = addr;
 
 	spin_lock(&xenbus_valloc_lock);
 	list_add(&node->next, &xenbus_valloc_pages);
@@ -514,8 +648,16 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
 	*vaddr = addr;
 	return 0;
 
- out_err_free_ballooned_pages:
-	free_xenballooned_pages(1, &node->page);
+ out_xenbus_unmap_ring:
+	if (!leaked)
+		xenbus_unmap_ring(dev, node->handles, node->nr_handles,
+				  addrs);
+	else
+		pr_alert("leaking %p size %u page(s)",
+			 addr, nr_grefs);
+ out_free_ballooned_pages:
+	if (!leaked)
+		free_xenballooned_pages(nr_grefs, node->hvm.pages);
  out_err:
 	kfree(node);
 	return err;
@@ -525,35 +667,37 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
 /**
  * xenbus_map_ring
  * @dev: xenbus device
- * @gnt_ref: grant reference
- * @handle: pointer to grant handle to be filled
- * @vaddr: address to be mapped to
+ * @gnt_refs: grant reference array
+ * @nr_grefs: number of grant reference
+ * @handles: pointer to grant handle to be filled
+ * @vaddrs: addresses to be mapped to
+ * @leaked: fail to clean up a failed map, caller should not free vaddr
  *
- * Map a page of memory into this domain from another domain's grant table.
+ * Map pages of memory into this domain from another domain's grant table.
  * xenbus_map_ring does not allocate the virtual address space (you must do
- * this yourself!). It only maps in the page to the specified address.
+ * this yourself!). It only maps in the pages to the specified address.
  * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
- * or -ENOMEM on error. If an error is returned, device will switch to
- * XenbusStateClosing and the error message will be saved in XenStore.
+ * or -ENOMEM / -EINVAL on error. If an error is returned, device will switch to
+ * XenbusStateClosing and the first error message will be saved in XenStore.
+ * Further more if we fail to map the ring, caller should check @leaked.
+ * If @leaked is not zero it means xenbus_map_ring fails to clean up, caller
+ * should not free the address space of @vaddr.
  */
-int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
-		    grant_handle_t *handle, void *vaddr)
+int xenbus_map_ring(struct xenbus_device *dev, grant_ref_t *gnt_refs,
+		    unsigned int nr_grefs, grant_handle_t *handles,
+		    unsigned long *vaddrs, bool *leaked)
 {
-	struct gnttab_map_grant_ref op;
-
-	gnttab_set_map_op(&op, (unsigned long)vaddr, GNTMAP_host_map, gnt_ref,
-			  dev->otherend_id);
+	phys_addr_t phys_addrs[XENBUS_MAX_RING_PAGES];
+	int i;
 
-	gnttab_batch_map(&op, 1);
+	if (nr_grefs > XENBUS_MAX_RING_PAGES)
+		return -EINVAL;
 
-	if (op.status != GNTST_okay) {
-		xenbus_dev_fatal(dev, op.status,
-				 "mapping in shared page %d from domain %d",
-				 gnt_ref, dev->otherend_id);
-	} else
-		*handle = op.handle;
+	for (i = 0; i < nr_grefs; i++)
+		phys_addrs[i] = (unsigned long)vaddrs[i];
 
-	return op.status;
+	return __xenbus_map_ring(dev, gnt_refs, nr_grefs, handles,
+				 phys_addrs, GNTMAP_host_map, leaked);
 }
 EXPORT_SYMBOL_GPL(xenbus_map_ring);
 
@@ -579,14 +723,15 @@ EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
 static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
 {
 	struct xenbus_map_node *node;
-	struct gnttab_unmap_grant_ref op = {
-		.host_addr = (unsigned long)vaddr,
-	};
+	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_PAGES];
 	unsigned int level;
+	int i;
+	bool leaked = false;
+	int err;
 
 	spin_lock(&xenbus_valloc_lock);
 	list_for_each_entry(node, &xenbus_valloc_pages, next) {
-		if (node->area->addr == vaddr) {
+		if (node->pv.area->addr == vaddr) {
 			list_del(&node->next);
 			goto found;
 		}
@@ -601,22 +746,41 @@ static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
 		return GNTST_bad_virt_addr;
 	}
 
-	op.handle = node->handle;
-	op.host_addr = arbitrary_virt_to_machine(
-		lookup_address((unsigned long)vaddr, &level)).maddr;
+	for (i = 0; i < node->nr_handles; i++) {
+		unsigned long addr;
+
+		memset(&unmap[i], 0, sizeof(unmap[i]));
+		addr = (unsigned long)vaddr + (PAGE_SIZE * i);
+		unmap[i].host_addr = arbitrary_virt_to_machine(
+			lookup_address(addr, &level)).maddr;
+		unmap[i].dev_bus_addr = 0;
+		unmap[i].handle = node->handles[i];
+	}
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
+	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
 		BUG();
 
-	if (op.status == GNTST_okay)
-		free_vm_area(node->area);
+	err = GNTST_okay;
+	leaked = false;
+	for (i = 0; i < node->nr_handles; i++) {
+		if (unmap[i].status != GNTST_okay) {
+			leaked = true;
+			xenbus_dev_error(dev, unmap[i].status,
+					 "unmapping page at handle %d error %d",
+					 node->handles[i], unmap[i].status);
+			err = unmap[i].status;
+			break;
+		}
+	}
+
+	if (!leaked)
+		free_vm_area(node->pv.area);
 	else
-		xenbus_dev_error(dev, op.status,
-				 "unmapping page at handle %d error %d",
-				 node->handle, op.status);
+		pr_alert("leaking VM area %p size %u page(s)",
+			 node->pv.area, node->nr_handles);
 
 	kfree(node);
-	return op.status;
+	return err;
 }
 
 static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
@@ -624,10 +788,12 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
 	int rv;
 	struct xenbus_map_node *node;
 	void *addr;
+	unsigned long addrs[XENBUS_MAX_RING_PAGES];
+	int i;
 
 	spin_lock(&xenbus_valloc_lock);
 	list_for_each_entry(node, &xenbus_valloc_pages, next) {
-		addr = pfn_to_kaddr(page_to_pfn(node->page));
+		addr = node->hvm.addr;
 		if (addr == vaddr) {
 			list_del(&node->next);
 			goto found;
@@ -643,12 +809,16 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
 		return GNTST_bad_virt_addr;
 	}
 
-	rv = xenbus_unmap_ring(dev, node->handle, addr);
+	for (i = 0; i < node->nr_handles; i++)
+		addrs[i] = (unsigned long)pfn_to_kaddr(page_to_pfn(node->hvm.pages[i]));
 
+	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
+			       addrs);
 	if (!rv)
-		free_xenballooned_pages(1, &node->page);
+		vunmap(vaddr);
 	else
-		WARN(1, "Leaking %p\n", vaddr);
+		WARN(1, "Leaking %p, size %u page(s)\n", vaddr,
+		     node->nr_handles);
 
 	kfree(node);
 	return rv;
@@ -657,29 +827,44 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
 /**
  * xenbus_unmap_ring
  * @dev: xenbus device
- * @handle: grant handle
- * @vaddr: addr to unmap
+ * @handles: grant handle array
+ * @nr_handles: number of handles in the array
+ * @vaddrs: addresses to unmap
  *
- * Unmap a page of memory in this domain that was imported from another domain.
+ * Unmap memory in this domain that was imported from another domain.
  * Returns 0 on success and returns GNTST_* on error
  * (see xen/include/interface/grant_table.h).
  */
 int xenbus_unmap_ring(struct xenbus_device *dev,
-		      grant_handle_t handle, void *vaddr)
+		      grant_handle_t *handles, unsigned int nr_handles,
+		      unsigned long *vaddrs)
 {
-	struct gnttab_unmap_grant_ref op;
+	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_PAGES];
+	int i;
+	int err;
 
-	gnttab_set_unmap_op(&op, (unsigned long)vaddr, GNTMAP_host_map, handle);
+	if (nr_handles > XENBUS_MAX_RING_PAGES)
+		return -EINVAL;
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
+	for (i = 0; i < nr_handles; i++)
+		gnttab_set_unmap_op(&unmap[i], vaddrs[i],
+				    GNTMAP_host_map, handles[i]);
+
+	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
 		BUG();
 
-	if (op.status != GNTST_okay)
-		xenbus_dev_error(dev, op.status,
-				 "unmapping page at handle %d error %d",
-				 handle, op.status);
+	err = GNTST_okay;
+	for (i = 0; i < nr_handles; i++) {
+		if (unmap[i].status != GNTST_okay) {
+			xenbus_dev_error(dev, unmap[i].status,
+					 "unmapping page at handle %d error %d",
+					 handles[i], unmap[i].status);
+			err = unmap[i].status;
+			break;
+		}
+	}
 
-	return op.status;
+	return err;
 }
 EXPORT_SYMBOL_GPL(xenbus_unmap_ring);
 
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index b0f1c9e..289c0b5 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -46,6 +46,10 @@
 #include <xen/interface/io/xenbus.h>
 #include <xen/interface/io/xs_wire.h>
 
+#define XENBUS_MAX_RING_PAGE_ORDER 4
+#define XENBUS_MAX_RING_PAGES      (1U << XENBUS_MAX_RING_PAGE_ORDER)
+#define INVALID_GRANT_HANDLE       (~0U)
+
 /* Register callback to watch this node. */
 struct xenbus_watch
 {
@@ -199,15 +203,19 @@ int xenbus_watch_pathfmt(struct xenbus_device *dev, struct xenbus_watch *watch,
 			 const char *pathfmt, ...);
 
 int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state new_state);
-int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn);
-int xenbus_map_ring_valloc(struct xenbus_device *dev,
-			   int gnt_ref, void **vaddr);
-int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
-			   grant_handle_t *handle, void *vaddr);
+int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
+		      unsigned int nr_pages, grant_ref_t *grefs);
+int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
+			   unsigned int nr_grefs, void **vaddr);
+int xenbus_map_ring(struct xenbus_device *dev,
+		    grant_ref_t *gnt_refs, unsigned int nr_grefs,
+		    grant_handle_t *handles, unsigned long *vaddrs,
+		    bool *leaked);
 
 int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr);
 int xenbus_unmap_ring(struct xenbus_device *dev,
-		      grant_handle_t handle, void *vaddr);
+		      grant_handle_t *handles, unsigned int nr_handles,
+		      unsigned long *vaddrs);
 
 int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port);
 int xenbus_free_evtchn(struct xenbus_device *dev, int port);
-- 
1.7.10.4

[PATCH 2/3] blkif: enable multi-page ring supporting

[Bob Liu]

Remove the 'DEPRECATED' and next patch will follow the protocol defined here to
support multi-page ring.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 xen/include/public/io/blkif.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
index 6baf7fb..d8b6b75 100644
--- a/xen/include/public/io/blkif.h
+++ b/xen/include/public/io/blkif.h
@@ -303,7 +303,7 @@
  *      Values:         <uint32_t>
  *      Default Value:  1
  *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
- *      Notes:          DEPRECATED, 2, 3
+ *      Notes:          2, 3
  *
  *      The size of the frontend allocated request ring buffer in units of
  *      machine pages.  The value must be a power of 2.
-- 
1.7.10.4

[PATCH v3 3/3] xen/block: add multi-page ring support

[Bob Liu]

Extend xen/block to support multi-page ring, so that more requests can be issued
by using more than one pages as the request ring between blkfront and backend.
As a result, the performance can get improved significantly.

We got some impressive improvements on our highend iscsi storage cluster backend.
If using 64 pages as the ring, the IOPS increased about 15 times for the
throughput testing and above doubled for the latency testing.

The reason was the limit on outstanding requests is 32 if use only one-page
ring, but in our case the iscsi lun was spread across about 100 physical drives,
32 was really not enough to keep them busy.

Change in V2:
* Rebased to 4.0-rc6
* Add description on how this protocol works into io/blkif.h

Change in V3:
* Follow the protocol defined in io/blkif.h on XEN tree

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 drivers/block/xen-blkback/blkback.c |    2 +-
 drivers/block/xen-blkback/common.h  |    3 +-
 drivers/block/xen-blkback/xenbus.c  |   84 +++++++++++++++++++-------
 drivers/block/xen-blkfront.c        |  112 ++++++++++++++++++++++++-----------
 4 files changed, 145 insertions(+), 56 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index a49c500..eaaafca 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -628,7 +628,7 @@ purge_gnt_list:
 		}
 
 		/* Shrink if we have more than xen_blkif_max_buffer_pages */
-		shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
+		shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages * blkif->nr_ring_pages);
 
 		if (log_stats && time_after(jiffies, blkif->st_print))
 			print_stats(blkif);
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 375d288..320ca35 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -254,7 +254,7 @@ struct backend_info;
 #define PERSISTENT_GNT_WAS_ACTIVE	1
 
 /* Number of requests that we can fit in a ring */
-#define XEN_BLKIF_REQS			32
+#define XEN_BLKIF_REQS			(32 * XENBUS_MAX_RING_PAGES)
 
 struct persistent_gnt {
 	struct page *page;
@@ -326,6 +326,7 @@ struct xen_blkif {
 	struct work_struct	free_work;
 	/* Thread shutdown wait queue. */
 	wait_queue_head_t	shutdown_wq;
+	int nr_ring_pages;
 };
 
 struct seg_buf {
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index ff30259..744f429 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -193,8 +193,8 @@ fail:
 	return ERR_PTR(-ENOMEM);
 }
 
-static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
-			 unsigned int evtchn)
+static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t *gref,
+			 unsigned int nr_grefs, unsigned int evtchn)
 {
 	int err;
 
@@ -202,7 +202,7 @@ static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
 	if (blkif->irq)
 		return 0;
 
-	err = xenbus_map_ring_valloc(blkif->be->dev, &gref, 1,
+	err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
 				     &blkif->blk_ring);
 	if (err < 0)
 		return err;
@@ -212,21 +212,21 @@ static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
 	{
 		struct blkif_sring *sring;
 		sring = (struct blkif_sring *)blkif->blk_ring;
-		BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
+		BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE * nr_grefs);
 		break;
 	}
 	case BLKIF_PROTOCOL_X86_32:
 	{
 		struct blkif_x86_32_sring *sring_x86_32;
 		sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
-		BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
+		BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE * nr_grefs);
 		break;
 	}
 	case BLKIF_PROTOCOL_X86_64:
 	{
 		struct blkif_x86_64_sring *sring_x86_64;
 		sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
-		BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
+		BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE * nr_grefs);
 		break;
 	}
 	default:
@@ -588,6 +588,11 @@ static int xen_blkbk_probe(struct xenbus_device *dev,
 	if (err)
 		goto fail;
 
+	err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-pages", "%u",
+			    XENBUS_MAX_RING_PAGES);
+	if (err)
+		goto fail;
+
 	err = xenbus_switch_state(dev, XenbusStateInitWait);
 	if (err)
 		goto fail;
@@ -852,22 +857,61 @@ again:
 static int connect_ring(struct backend_info *be)
 {
 	struct xenbus_device *dev = be->dev;
-	unsigned long ring_ref;
-	unsigned int evtchn;
+	unsigned int ring_ref[XENBUS_MAX_RING_PAGES];
+	unsigned int evtchn, nr_grefs;
 	unsigned int pers_grants;
 	char protocol[64] = "";
 	int err;
 
 	DPRINTK("%s", dev->otherend);
-
-	err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
-			    &ring_ref, "event-channel", "%u", &evtchn, NULL);
-	if (err) {
-		xenbus_dev_fatal(dev, err,
-				 "reading %s/ring-ref and event-channel",
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "event-channel", "%u",
+			  &evtchn);
+	if (err != 1) {
+		err = -EINVAL;
+		xenbus_dev_fatal(dev, err, "reading %s/event-channel",
 				 dev->otherend);
 		return err;
 	}
+	pr_info(DRV_PFX "event-channel %u\n", evtchn);
+
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "num-ring-pages", "%u",
+			  &nr_grefs);
+	if (err != 1) {
+		err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-ref",
+				  "%u", &ring_ref[0]);
+		if (err != 1) {
+			err = -EINVAL;
+			xenbus_dev_fatal(dev, err, "reading %s/ring-ref",
+					 dev->otherend);
+			return err;
+		}
+		nr_grefs = 1;
+		pr_info(DRV_PFX "%s:using single page: ring-ref %d\n",
+				 dev->otherend, ring_ref[0]);
+	} else {
+		unsigned int i;
+
+		if (nr_grefs > XENBUS_MAX_RING_PAGES) {
+			err = -EINVAL;
+			xenbus_dev_fatal(dev, err, "%s/request %d ring pages exceed max",
+					 dev->otherend, nr_grefs);
+			return err;
+		}
+		for (i = 0; i < nr_grefs; i++) {
+			char ring_ref_name[15];
+
+			snprintf(ring_ref_name, sizeof(ring_ref_name), "ring-ref%u", i);
+			err = xenbus_scanf(XBT_NIL, dev->otherend,
+					   ring_ref_name, "%d", &ring_ref[i]);
+			if (err != 1) {
+				err = -EINVAL;
+				xenbus_dev_fatal(dev, err, "reading %s/%s",
+						 dev->otherend, ring_ref_name);
+				return err;
+			}
+			pr_info(DRV_PFX "ring-ref%u: %d\n", i, ring_ref[i]);
+		}
+	}
 
 	be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
 	err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
@@ -892,16 +936,16 @@ static int connect_ring(struct backend_info *be)
 
 	be->blkif->vbd.feature_gnt_persistent = pers_grants;
 	be->blkif->vbd.overflow_max_grants = 0;
+	be->blkif->nr_ring_pages = nr_grefs;
 
-	pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
-		ring_ref, evtchn, be->blkif->blk_protocol, protocol,
-		pers_grants ? "persistent grants" : "");
+	pr_info(DRV_PFX "ring-pages:%d, event-channel %d, protocol %d (%s) %s\n",
+			nr_grefs, evtchn, be->blkif->blk_protocol, protocol,
+			pers_grants ? "persistent grants" : "");
 
 	/* Map the shared frame, irq etc. */
-	err = xen_blkif_map(be->blkif, ring_ref, evtchn);
+	err = xen_blkif_map(be->blkif, ring_ref, nr_grefs, evtchn);
 	if (err) {
-		xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
-				 ring_ref, evtchn);
+		xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
 		return err;
 	}
 
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 2c61cf8..b590b24 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -98,7 +98,12 @@ static unsigned int xen_blkif_max_segments = 32;
 module_param_named(max, xen_blkif_max_segments, int, S_IRUGO);
 MODULE_PARM_DESC(max, "Maximum amount of segments in indirect requests (default is 32)");
 
-#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
+static unsigned int xen_blkif_max_ring_pages = 1;
+module_param_named(max_ring_pages, xen_blkif_max_ring_pages, int, 0644);
+MODULE_PARM_DESC(max_ring_pages, "Maximum amount of pages to be used as the ring");
+
+#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE * info->nr_ring_pages)
+#define BLK_MAX_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE * XENBUS_MAX_RING_PAGES)
 
 /*
  * We have one of these per vbd, whether ide, scsi or 'other'.  They
@@ -114,13 +119,14 @@ struct blkfront_info
 	int vdevice;
 	blkif_vdev_t handle;
 	enum blkif_state connected;
-	int ring_ref;
+	int ring_ref[XENBUS_MAX_RING_PAGES];
+	unsigned int nr_ring_pages;
 	struct blkif_front_ring ring;
 	unsigned int evtchn, irq;
 	struct request_queue *rq;
 	struct work_struct work;
 	struct gnttab_free_callback callback;
-	struct blk_shadow shadow[BLK_RING_SIZE];
+	struct blk_shadow shadow[BLK_MAX_RING_SIZE];
 	struct list_head grants;
 	struct list_head indirect_pages;
 	unsigned int persistent_gnts_c;
@@ -139,8 +145,6 @@ static unsigned int nr_minors;
 static unsigned long *minors;
 static DEFINE_SPINLOCK(minor_lock);
 
-#define MAXIMUM_OUTSTANDING_BLOCK_REQS \
-	(BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
 #define GRANT_INVALID_REF	0
 
 #define PARTS_PER_DISK		16
@@ -1033,12 +1037,15 @@ free_shadow:
 	flush_work(&info->work);
 
 	/* Free resources associated with old device channel. */
-	if (info->ring_ref != GRANT_INVALID_REF) {
-		gnttab_end_foreign_access(info->ring_ref, 0,
-					  (unsigned long)info->ring.sring);
-		info->ring_ref = GRANT_INVALID_REF;
-		info->ring.sring = NULL;
+	for (i = 0; i < info->nr_ring_pages; i++) {
+		if (info->ring_ref[i] != GRANT_INVALID_REF) {
+			gnttab_end_foreign_access(info->ring_ref[i], 0, 0);
+			info->ring_ref[i] = GRANT_INVALID_REF;
+		}
 	}
+	free_pages((unsigned long)info->ring.sring, get_order(info->nr_ring_pages * PAGE_SIZE));
+	info->ring.sring = NULL;
+
 	if (info->irq)
 		unbind_from_irqhandler(info->irq, info);
 	info->evtchn = info->irq = 0;
@@ -1245,26 +1252,30 @@ static int setup_blkring(struct xenbus_device *dev,
 			 struct blkfront_info *info)
 {
 	struct blkif_sring *sring;
-	grant_ref_t gref;
-	int err;
+	int err, i;
+	unsigned long ring_size = info->nr_ring_pages * PAGE_SIZE;
+	grant_ref_t gref[XENBUS_MAX_RING_PAGES];
 
-	info->ring_ref = GRANT_INVALID_REF;
+	for (i = 0; i < XENBUS_MAX_RING_PAGES; i++)
+		info->ring_ref[i] = GRANT_INVALID_REF;
 
-	sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
+	sring = (struct blkif_sring *)__get_free_pages(GFP_NOIO | __GFP_HIGH,
+						       get_order(ring_size));
 	if (!sring) {
 		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
 		return -ENOMEM;
 	}
 	SHARED_RING_INIT(sring);
-	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+	FRONT_RING_INIT(&info->ring, sring, ring_size);
 
-	err = xenbus_grant_ring(dev, info->ring.sring, 1, &gref);
+	err = xenbus_grant_ring(dev, info->ring.sring, info->nr_ring_pages, gref);
 	if (err < 0) {
 		free_page((unsigned long)sring);
 		info->ring.sring = NULL;
 		goto fail;
 	}
-	info->ring_ref = gref;
+	for (i = 0; i < info->nr_ring_pages; i++)
+		info->ring_ref[i] = gref[i];
 
 	err = xenbus_alloc_evtchn(dev, &info->evtchn);
 	if (err)
@@ -1292,7 +1303,15 @@ static int talk_to_blkback(struct xenbus_device *dev,
 {
 	const char *message = NULL;
 	struct xenbus_transaction xbt;
-	int err;
+	int err, i;
+	unsigned int max_pages = 0;
+
+	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+			   "max-ring-pages", "%u", &max_pages);
+	if (err != 1)
+		info->nr_ring_pages = 1;
+	else
+		info->nr_ring_pages = min(xen_blkif_max_ring_pages, max_pages);
 
 	/* Create shared ring, alloc event channel. */
 	err = setup_blkring(dev, info);
@@ -1306,11 +1325,31 @@ again:
 		goto destroy_blkring;
 	}
 
-	err = xenbus_printf(xbt, dev->nodename,
-			    "ring-ref", "%u", info->ring_ref);
-	if (err) {
-		message = "writing ring-ref";
-		goto abort_transaction;
+	if (info->nr_ring_pages == 1) {
+		err = xenbus_printf(xbt, dev->nodename,
+				    "ring-ref", "%u", info->ring_ref[0]);
+		if (err) {
+			message = "writing ring-ref";
+			goto abort_transaction;
+		}
+	} else {
+		err = xenbus_printf(xbt, dev->nodename,
+				    "num-ring-pages", "%u", info->nr_ring_pages);
+		if (err) {
+			message = "writing num-ring-pages";
+			goto abort_transaction;
+		}
+
+		for (i = 0; i < info->nr_ring_pages; i++) {
+			char ring_ref_name[15];
+			sprintf(ring_ref_name, "ring-ref%d", i);
+			err = xenbus_printf(xbt, dev->nodename,
+					ring_ref_name, "%d", info->ring_ref[i]);
+			if (err) {
+				message = "writing ring-ref";
+				goto abort_transaction;
+			}
+		}
 	}
 	err = xenbus_printf(xbt, dev->nodename,
 			    "event-channel", "%u", info->evtchn);
@@ -1338,6 +1377,7 @@ again:
 		goto destroy_blkring;
 	}
 
+	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
 	xenbus_switch_state(dev, XenbusStateInitialised);
 
 	return 0;
@@ -1422,21 +1462,13 @@ static int blkfront_probe(struct xenbus_device *dev,
 	info->connected = BLKIF_STATE_DISCONNECTED;
 	INIT_WORK(&info->work, blkif_restart_queue);
 
-	for (i = 0; i < BLK_RING_SIZE; i++)
+	for (i = 0; i < BLK_MAX_RING_SIZE; i++)
 		info->shadow[i].req.u.rw.id = i+1;
-	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
 
 	/* Front end dir is a number, which is used as the id. */
 	info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
 	dev_set_drvdata(&dev->dev, info);
 
-	err = talk_to_blkback(dev, info);
-	if (err) {
-		kfree(info);
-		dev_set_drvdata(&dev->dev, NULL);
-		return err;
-	}
-
 	return 0;
 }
 
@@ -1476,7 +1508,7 @@ static int blkif_recover(struct blkfront_info *info)
 
 	/* Stage 2: Set up free list. */
 	memset(&info->shadow, 0, sizeof(info->shadow));
-	for (i = 0; i < BLK_RING_SIZE; i++)
+	for (i = 0; i < BLK_MAX_RING_SIZE; i++)
 		info->shadow[i].req.u.rw.id = i+1;
 	info->shadow_free = info->ring.req_prod_pvt;
 	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
@@ -1906,8 +1938,17 @@ static void blkback_changed(struct xenbus_device *dev,
 	dev_dbg(&dev->dev, "blkfront:blkback_changed to state %d.\n", backend_state);
 
 	switch (backend_state) {
-	case XenbusStateInitialising:
 	case XenbusStateInitWait:
+		/*
+		 * Talk to blkback after backend enter InitWait so we can know
+		 * the 'max-ring-pages' of backend.
+		 */
+		if (talk_to_blkback(dev, info)) {
+			kfree(info);
+			dev_set_drvdata(&dev->dev, NULL);
+		}
+		break;
+	case XenbusStateInitialising:
 	case XenbusStateInitialised:
 	case XenbusStateReconfiguring:
 	case XenbusStateReconfigured:
@@ -2088,6 +2129,9 @@ static int __init xlblk_init(void)
 {
 	int ret;
 
+	if (xen_blkif_max_ring_pages > XENBUS_MAX_RING_PAGES)
+		return -EINVAL;
+
 	if (!xen_domain())
 		return -ENODEV;
 
-- 
1.7.10.4

Re: [PATCH v6 1/3] xenbus_client: Extend interface to support multi-page ring

[Juergen Gross]

On 04/03/2015 08:44 AM, Bob Liu wrote:
> From: Wei Liu <wei.liu2@citrix.com>
>
> Originally Xen PV drivers only use single-page ring to pass along
> information. This might limit the throughput between frontend and
> backend.
>
> The patch extends Xenbus driver to support multi-page ring, which in
> general should improve throughput if ring is the bottleneck. Changes to
> various frontend / backend to adapt to the new interface are also
> included.
>
> Affected Xen drivers:
> * blkfront/back
> * netfront/back
> * pcifront/back
> * scsifront/back
>
> The interface is documented, as before, in xenbus_client.c.
>
> Change in V2:
> * allow ring has arbitrary number of pages <= XENBUS_MAX_RING_PAGES
>
> Change in V3:
> * update function prototypes
> * carefully deal with types of different sizes
>
> Change in V4:
> * use PAGE_KERNEL instead of PAGE_KERNEL_IO to avoid breakage on Arm
>
> Change in V5:
> * fix off-by-one error and other minor glitches spotted by Mathew Daley
>
> Change in V6:
> * add pvscsi driver support by Bob Liu
>
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> Signed-off-by: Bob Liu <bob.liu@oracle.com>
> Cc: Konrad Wilk <konrad.wilk@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Acked-by: Juergen Gross <jgross@suse.com>


Juergen

> ---
>   drivers/block/xen-blkback/xenbus.c |    5 +-
>   drivers/block/xen-blkfront.c       |    5 +-
>   drivers/net/xen-netback/netback.c  |    4 +-
>   drivers/net/xen-netfront.c         |    9 +-
>   drivers/pci/xen-pcifront.c         |    5 +-
>   drivers/scsi/xen-scsifront.c       |    5 +-
>   drivers/xen/xen-pciback/xenbus.c   |    2 +-
>   drivers/xen/xen-scsiback.c         |    2 +-
>   drivers/xen/xenbus/xenbus_client.c |  387 ++++++++++++++++++++++++++----------
>   include/xen/xenbus.h               |   20 +-
>   10 files changed, 321 insertions(+), 123 deletions(-)
>
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index e3afe97..ff30259 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -193,7 +193,7 @@ fail:
>   	return ERR_PTR(-ENOMEM);
>   }
>
> -static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
> +static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
>   			 unsigned int evtchn)
>   {
>   	int err;
> @@ -202,7 +202,8 @@ static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
>   	if (blkif->irq)
>   		return 0;
>
> -	err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
> +	err = xenbus_map_ring_valloc(blkif->be->dev, &gref, 1,
> +				     &blkif->blk_ring);
>   	if (err < 0)
>   		return err;
>
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 37779e4..2c61cf8 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -1245,6 +1245,7 @@ static int setup_blkring(struct xenbus_device *dev,
>   			 struct blkfront_info *info)
>   {
>   	struct blkif_sring *sring;
> +	grant_ref_t gref;
>   	int err;
>
>   	info->ring_ref = GRANT_INVALID_REF;
> @@ -1257,13 +1258,13 @@ static int setup_blkring(struct xenbus_device *dev,
>   	SHARED_RING_INIT(sring);
>   	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
>
> -	err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
> +	err = xenbus_grant_ring(dev, info->ring.sring, 1, &gref);
>   	if (err < 0) {
>   		free_page((unsigned long)sring);
>   		info->ring.sring = NULL;
>   		goto fail;
>   	}
> -	info->ring_ref = err;
> +	info->ring_ref = gref;
>
>   	err = xenbus_alloc_evtchn(dev, &info->evtchn);
>   	if (err)
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 997cf09..865203f 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1782,7 +1782,7 @@ int xenvif_map_frontend_rings(struct xenvif_queue *queue,
>   	int err = -ENOMEM;
>
>   	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
> -				     tx_ring_ref, &addr);
> +				     &tx_ring_ref, 1, &addr);
>   	if (err)
>   		goto err;
>
> @@ -1790,7 +1790,7 @@ int xenvif_map_frontend_rings(struct xenvif_queue *queue,
>   	BACK_RING_INIT(&queue->tx, txs, PAGE_SIZE);
>
>   	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
> -				     rx_ring_ref, &addr);
> +				     &rx_ring_ref, 1, &addr);
>   	if (err)
>   		goto err;
>
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index e9b960f..13f5e7f 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -1486,6 +1486,7 @@ static int setup_netfront(struct xenbus_device *dev,
>   {
>   	struct xen_netif_tx_sring *txs;
>   	struct xen_netif_rx_sring *rxs;
> +	grant_ref_t gref;
>   	int err;
>
>   	queue->tx_ring_ref = GRANT_INVALID_REF;
> @@ -1502,10 +1503,10 @@ static int setup_netfront(struct xenbus_device *dev,
>   	SHARED_RING_INIT(txs);
>   	FRONT_RING_INIT(&queue->tx, txs, PAGE_SIZE);
>
> -	err = xenbus_grant_ring(dev, virt_to_mfn(txs));
> +	err = xenbus_grant_ring(dev, txs, 1, &gref);
>   	if (err < 0)
>   		goto grant_tx_ring_fail;
> -	queue->tx_ring_ref = err;
> +	queue->tx_ring_ref = gref;
>
>   	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
>   	if (!rxs) {
> @@ -1516,10 +1517,10 @@ static int setup_netfront(struct xenbus_device *dev,
>   	SHARED_RING_INIT(rxs);
>   	FRONT_RING_INIT(&queue->rx, rxs, PAGE_SIZE);
>
> -	err = xenbus_grant_ring(dev, virt_to_mfn(rxs));
> +	err = xenbus_grant_ring(dev, rxs, 1, &gref);
>   	if (err < 0)
>   		goto grant_rx_ring_fail;
> -	queue->rx_ring_ref = err;
> +	queue->rx_ring_ref = gref;
>
>   	if (feature_split_evtchn)
>   		err = setup_netfront_split(queue);
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index b1ffebe..7cfd2db 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -777,12 +777,13 @@ static int pcifront_publish_info(struct pcifront_device *pdev)
>   {
>   	int err = 0;
>   	struct xenbus_transaction trans;
> +	grant_ref_t gref;
>
> -	err = xenbus_grant_ring(pdev->xdev, virt_to_mfn(pdev->sh_info));
> +	err = xenbus_grant_ring(pdev->xdev, pdev->sh_info, 1, &gref);
>   	if (err < 0)
>   		goto out;
>
> -	pdev->gnt_ref = err;
> +	pdev->gnt_ref = gref;
>
>   	err = xenbus_alloc_evtchn(pdev->xdev, &pdev->evtchn);
>   	if (err)
> diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
> index 34199d2..2e9de74 100644
> --- a/drivers/scsi/xen-scsifront.c
> +++ b/drivers/scsi/xen-scsifront.c
> @@ -644,6 +644,7 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
>   {
>   	struct xenbus_device *dev = info->dev;
>   	struct vscsiif_sring *sring;
> +	grant_ref_t gref;
>   	int err = -ENOMEM;
>
>   	/***** Frontend to Backend ring start *****/
> @@ -656,14 +657,14 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
>   	SHARED_RING_INIT(sring);
>   	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
>
> -	err = xenbus_grant_ring(dev, virt_to_mfn(sring));
> +	err = xenbus_grant_ring(dev, sring, 1, &gref);
>   	if (err < 0) {
>   		free_page((unsigned long)sring);
>   		xenbus_dev_fatal(dev, err,
>   			"fail to grant shared ring (Front to Back)");
>   		return err;
>   	}
> -	info->ring_ref = err;
> +	info->ring_ref = gref;
>
>   	err = xenbus_alloc_evtchn(dev, &info->evtchn);
>   	if (err) {
> diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
> index fe17c80..98bc345 100644
> --- a/drivers/xen/xen-pciback/xenbus.c
> +++ b/drivers/xen/xen-pciback/xenbus.c
> @@ -113,7 +113,7 @@ static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref,
>   		"Attaching to frontend resources - gnt_ref=%d evtchn=%d\n",
>   		gnt_ref, remote_evtchn);
>
> -	err = xenbus_map_ring_valloc(pdev->xdev, gnt_ref, &vaddr);
> +	err = xenbus_map_ring_valloc(pdev->xdev, &gnt_ref, 1, &vaddr);
>   	if (err < 0) {
>   		xenbus_dev_fatal(pdev->xdev, err,
>   				"Error mapping other domain page in ours.");
> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
> index 42bd55a..6cc753d 100644
> --- a/drivers/xen/xen-scsiback.c
> +++ b/drivers/xen/xen-scsiback.c
> @@ -810,7 +810,7 @@ static int scsiback_init_sring(struct vscsibk_info *info, grant_ref_t ring_ref,
>   	if (info->irq)
>   		return -1;
>
> -	err = xenbus_map_ring_valloc(info->dev, ring_ref, &area);
> +	err = xenbus_map_ring_valloc(info->dev, &ring_ref, 1, &area);
>   	if (err)
>   		return err;
>
> diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
> index ca74410..96b2011 100644
> --- a/drivers/xen/xenbus/xenbus_client.c
> +++ b/drivers/xen/xenbus/xenbus_client.c
> @@ -52,17 +52,25 @@
>   struct xenbus_map_node {
>   	struct list_head next;
>   	union {
> -		struct vm_struct *area; /* PV */
> -		struct page *page;     /* HVM */
> +		struct {
> +			struct vm_struct *area;
> +		} pv;
> +		struct {
> +			struct page *pages[XENBUS_MAX_RING_PAGES];
> +			void *addr;
> +		} hvm;
>   	};
> -	grant_handle_t handle;
> +	grant_handle_t handles[XENBUS_MAX_RING_PAGES];
> +	unsigned int   nr_handles;
>   };
>
>   static DEFINE_SPINLOCK(xenbus_valloc_lock);
>   static LIST_HEAD(xenbus_valloc_pages);
>
>   struct xenbus_ring_ops {
> -	int (*map)(struct xenbus_device *dev, int gnt, void **vaddr);
> +	int (*map)(struct xenbus_device *dev,
> +		   grant_ref_t *gnt_refs, unsigned int nr_grefs,
> +		   void **vaddr);
>   	int (*unmap)(struct xenbus_device *dev, void *vaddr);
>   };
>
> @@ -355,17 +363,39 @@ static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
>   /**
>    * xenbus_grant_ring
>    * @dev: xenbus device
> - * @ring_mfn: mfn of ring to grant
> -
> - * Grant access to the given @ring_mfn to the peer of the given device.  Return
> - * a grant reference on success, or -errno on error. On error, the device will
> - * switch to XenbusStateClosing, and the error will be saved in the store.
> + * @vaddr: starting virtual address of the ring
> + * @nr_pages: number of pages to be granted
> + * @grefs: grant reference array to be filled in
> + *
> + * Grant access to the given @vaddr to the peer of the given device.
> + * Then fill in @grefs with grant references.  Return 0 on success, or
> + * -errno on error.  On error, the device will switch to
> + * XenbusStateClosing, and the error will be saved in the store.
>    */
> -int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn)
> +int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
> +		      unsigned int nr_pages, grant_ref_t *grefs)
>   {
> -	int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0);
> -	if (err < 0)
> -		xenbus_dev_fatal(dev, err, "granting access to ring page");
> +	int err;
> +	int i, j;
> +
> +	for (i = 0; i < nr_pages; i++) {
> +		unsigned long addr = (unsigned long)vaddr +
> +			(PAGE_SIZE * i);
> +		err = gnttab_grant_foreign_access(dev->otherend_id,
> +						  virt_to_mfn(addr), 0);
> +		if (err < 0) {
> +			xenbus_dev_fatal(dev, err,
> +					 "granting access to ring page");
> +			goto fail;
> +		}
> +		grefs[i] = err;
> +	}
> +
> +	return 0;
> +
> +fail:
> +	for (j = 0; j < i; j++)
> +		gnttab_end_foreign_access_ref(grefs[j], 0);
>   	return err;
>   }
>   EXPORT_SYMBOL_GPL(xenbus_grant_ring);
> @@ -419,62 +449,130 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
>   /**
>    * xenbus_map_ring_valloc
>    * @dev: xenbus device
> - * @gnt_ref: grant reference
> + * @gnt_refs: grant reference array
> + * @nr_grefs: number of grant references
>    * @vaddr: pointer to address to be filled out by mapping
>    *
> - * Based on Rusty Russell's skeleton driver's map_page.
> - * Map a page of memory into this domain from another domain's grant table.
> - * xenbus_map_ring_valloc allocates a page of virtual address space, maps the
> - * page to that address, and sets *vaddr to that address.
> - * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
> - * or -ENOMEM on error. If an error is returned, device will switch to
> + * Map @nr_grefs pages of memory into this domain from another
> + * domain's grant table.  xenbus_map_ring_valloc allocates @nr_grefs
> + * pages of virtual address space, maps the pages to that address, and
> + * sets *vaddr to that address.  Returns 0 on success, and GNTST_*
> + * (see xen/include/interface/grant_table.h) or -ENOMEM / -EINVAL on
> + * error. If an error is returned, device will switch to
>    * XenbusStateClosing and the error message will be saved in XenStore.
>    */
> -int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
> +int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
> +			   unsigned int nr_grefs, void **vaddr)
>   {
> -	return ring_ops->map(dev, gnt_ref, vaddr);
> +	return ring_ops->map(dev, gnt_refs, nr_grefs, vaddr);
>   }
>   EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
>
> +/* N.B. sizeof(phys_addr_t) doesn't always equal to sizeof(unsigned
> + * long), e.g. 32-on-64.  Caller is responsible for preparing the
> + * right array to feed into this function */
> +static int __xenbus_map_ring(struct xenbus_device *dev,
> +			     grant_ref_t *gnt_refs,
> +			     unsigned int nr_grefs,
> +			     grant_handle_t *handles,
> +			     phys_addr_t *addrs,
> +			     unsigned int flags,
> +			     bool *leaked)
> +{
> +	struct gnttab_map_grant_ref map[XENBUS_MAX_RING_PAGES];
> +	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_PAGES];
> +	int i, j;
> +	int err = GNTST_okay;
> +
> +	if (nr_grefs > XENBUS_MAX_RING_PAGES)
> +		return -EINVAL;
> +
> +	for (i = 0; i < nr_grefs; i++) {
> +		memset(&map[i], 0, sizeof(map[i]));
> +		gnttab_set_map_op(&map[i], addrs[i], flags, gnt_refs[i],
> +				  dev->otherend_id);
> +		handles[i] = INVALID_GRANT_HANDLE;
> +	}
> +
> +	gnttab_batch_map(map, i);
> +
> +	for (i = 0; i < nr_grefs; i++) {
> +		if (map[i].status != GNTST_okay) {
> +			err = map[i].status;
> +			xenbus_dev_fatal(dev, map[i].status,
> +					 "mapping in shared page %d from domain %d",
> +					 gnt_refs[i], dev->otherend_id);
> +			goto fail;
> +		} else
> +			handles[i] = map[i].handle;
> +	}
> +
> +	return GNTST_okay;
> +
> + fail:
> +	for (i = j = 0; i < nr_grefs; i++) {
> +		if (handles[i] != INVALID_GRANT_HANDLE) {
> +			memset(&unmap[j], 0, sizeof(unmap[j]));
> +			gnttab_set_unmap_op(&unmap[j], (phys_addr_t)addrs[i],
> +					    GNTMAP_host_map, handles[i]);
> +			j++;
> +		}
> +	}
> +
> +	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, j))
> +		BUG();
> +
> +	*leaked = false;
> +	for (i = 0; i < j; i++) {
> +		if (unmap[i].status != GNTST_okay) {
> +			*leaked = true;
> +			break;
> +		}
> +	}
> +
> +	return err;
> +}
> +
>   static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
> -				     int gnt_ref, void **vaddr)
> +				     grant_ref_t *gnt_refs,
> +				     unsigned int nr_grefs,
> +				     void **vaddr)
>   {
> -	struct gnttab_map_grant_ref op = {
> -		.flags = GNTMAP_host_map | GNTMAP_contains_pte,
> -		.ref   = gnt_ref,
> -		.dom   = dev->otherend_id,
> -	};
>   	struct xenbus_map_node *node;
>   	struct vm_struct *area;
> -	pte_t *pte;
> +	pte_t *ptes[XENBUS_MAX_RING_PAGES];
> +	phys_addr_t phys_addrs[XENBUS_MAX_RING_PAGES];
> +	int err = GNTST_okay;
> +	int i;
> +	bool leaked;
>
>   	*vaddr = NULL;
>
> +	if (nr_grefs > XENBUS_MAX_RING_PAGES)
> +		return -EINVAL;
> +
>   	node = kzalloc(sizeof(*node), GFP_KERNEL);
>   	if (!node)
>   		return -ENOMEM;
>
> -	area = alloc_vm_area(PAGE_SIZE, &pte);
> +	area = alloc_vm_area(PAGE_SIZE * nr_grefs, ptes);
>   	if (!area) {
>   		kfree(node);
>   		return -ENOMEM;
>   	}
>
> -	op.host_addr = arbitrary_virt_to_machine(pte).maddr;
> +	for (i = 0; i < nr_grefs; i++)
> +		phys_addrs[i] = arbitrary_virt_to_machine(ptes[i]).maddr;
>
> -	gnttab_batch_map(&op, 1);
> -
> -	if (op.status != GNTST_okay) {
> -		free_vm_area(area);
> -		kfree(node);
> -		xenbus_dev_fatal(dev, op.status,
> -				 "mapping in shared page %d from domain %d",
> -				 gnt_ref, dev->otherend_id);
> -		return op.status;
> -	}
> +	err = __xenbus_map_ring(dev, gnt_refs, nr_grefs, node->handles,
> +				phys_addrs,
> +				GNTMAP_host_map | GNTMAP_contains_pte,
> +				&leaked);
> +	if (err)
> +		goto failed;
>
> -	node->handle = op.handle;
> -	node->area = area;
> +	node->nr_handles = nr_grefs;
> +	node->pv.area = area;
>
>   	spin_lock(&xenbus_valloc_lock);
>   	list_add(&node->next, &xenbus_valloc_pages);
> @@ -482,14 +580,33 @@ static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
>
>   	*vaddr = area->addr;
>   	return 0;
> +
> +failed:
> +	if (!leaked)
> +		free_vm_area(area);
> +	else
> +		pr_alert("leaking VM area %p size %u page(s)", area, nr_grefs);
> +
> +	kfree(node);
> +	return err;
>   }
>
>   static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
> -				      int gnt_ref, void **vaddr)
> +				      grant_ref_t *gnt_ref,
> +				      unsigned int nr_grefs,
> +				      void **vaddr)
>   {
>   	struct xenbus_map_node *node;
> +	int i;
>   	int err;
>   	void *addr;
> +	bool leaked = false;
> +	/* Why do we need two arrays? See comment of __xenbus_map_ring */
> +	phys_addr_t phys_addrs[XENBUS_MAX_RING_PAGES];
> +	unsigned long addrs[XENBUS_MAX_RING_PAGES];
> +
> +	if (nr_grefs > XENBUS_MAX_RING_PAGES)
> +		return -EINVAL;
>
>   	*vaddr = NULL;
>
> @@ -497,15 +614,32 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
>   	if (!node)
>   		return -ENOMEM;
>
> -	err = alloc_xenballooned_pages(1, &node->page, false /* lowmem */);
> +	err = alloc_xenballooned_pages(nr_grefs, node->hvm.pages,
> +				       false /* lowmem */);
>   	if (err)
>   		goto out_err;
>
> -	addr = pfn_to_kaddr(page_to_pfn(node->page));
> +	for (i = 0; i < nr_grefs; i++) {
> +		unsigned long pfn = page_to_pfn(node->hvm.pages[i]);
> +		phys_addrs[i] = (unsigned long)pfn_to_kaddr(pfn);
> +		addrs[i] = (unsigned long)pfn_to_kaddr(pfn);
> +	}
> +
> +	err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
> +				phys_addrs, GNTMAP_host_map, &leaked);
> +	node->nr_handles = nr_grefs;
>
> -	err = xenbus_map_ring(dev, gnt_ref, &node->handle, addr);
>   	if (err)
> -		goto out_err_free_ballooned_pages;
> +		goto out_free_ballooned_pages;
> +
> +	addr = vmap(node->hvm.pages, nr_grefs, VM_MAP | VM_IOREMAP,
> +		    PAGE_KERNEL);
> +	if (!addr) {
> +		err = -ENOMEM;
> +		goto out_xenbus_unmap_ring;
> +	}
> +
> +	node->hvm.addr = addr;
>
>   	spin_lock(&xenbus_valloc_lock);
>   	list_add(&node->next, &xenbus_valloc_pages);
> @@ -514,8 +648,16 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
>   	*vaddr = addr;
>   	return 0;
>
> - out_err_free_ballooned_pages:
> -	free_xenballooned_pages(1, &node->page);
> + out_xenbus_unmap_ring:
> +	if (!leaked)
> +		xenbus_unmap_ring(dev, node->handles, node->nr_handles,
> +				  addrs);
> +	else
> +		pr_alert("leaking %p size %u page(s)",
> +			 addr, nr_grefs);
> + out_free_ballooned_pages:
> +	if (!leaked)
> +		free_xenballooned_pages(nr_grefs, node->hvm.pages);
>    out_err:
>   	kfree(node);
>   	return err;
> @@ -525,35 +667,37 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
>   /**
>    * xenbus_map_ring
>    * @dev: xenbus device
> - * @gnt_ref: grant reference
> - * @handle: pointer to grant handle to be filled
> - * @vaddr: address to be mapped to
> + * @gnt_refs: grant reference array
> + * @nr_grefs: number of grant reference
> + * @handles: pointer to grant handle to be filled
> + * @vaddrs: addresses to be mapped to
> + * @leaked: fail to clean up a failed map, caller should not free vaddr
>    *
> - * Map a page of memory into this domain from another domain's grant table.
> + * Map pages of memory into this domain from another domain's grant table.
>    * xenbus_map_ring does not allocate the virtual address space (you must do
> - * this yourself!). It only maps in the page to the specified address.
> + * this yourself!). It only maps in the pages to the specified address.
>    * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
> - * or -ENOMEM on error. If an error is returned, device will switch to
> - * XenbusStateClosing and the error message will be saved in XenStore.
> + * or -ENOMEM / -EINVAL on error. If an error is returned, device will switch to
> + * XenbusStateClosing and the first error message will be saved in XenStore.
> + * Further more if we fail to map the ring, caller should check @leaked.
> + * If @leaked is not zero it means xenbus_map_ring fails to clean up, caller
> + * should not free the address space of @vaddr.
>    */
> -int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
> -		    grant_handle_t *handle, void *vaddr)
> +int xenbus_map_ring(struct xenbus_device *dev, grant_ref_t *gnt_refs,
> +		    unsigned int nr_grefs, grant_handle_t *handles,
> +		    unsigned long *vaddrs, bool *leaked)
>   {
> -	struct gnttab_map_grant_ref op;
> -
> -	gnttab_set_map_op(&op, (unsigned long)vaddr, GNTMAP_host_map, gnt_ref,
> -			  dev->otherend_id);
> +	phys_addr_t phys_addrs[XENBUS_MAX_RING_PAGES];
> +	int i;
>
> -	gnttab_batch_map(&op, 1);
> +	if (nr_grefs > XENBUS_MAX_RING_PAGES)
> +		return -EINVAL;
>
> -	if (op.status != GNTST_okay) {
> -		xenbus_dev_fatal(dev, op.status,
> -				 "mapping in shared page %d from domain %d",
> -				 gnt_ref, dev->otherend_id);
> -	} else
> -		*handle = op.handle;
> +	for (i = 0; i < nr_grefs; i++)
> +		phys_addrs[i] = (unsigned long)vaddrs[i];
>
> -	return op.status;
> +	return __xenbus_map_ring(dev, gnt_refs, nr_grefs, handles,
> +				 phys_addrs, GNTMAP_host_map, leaked);
>   }
>   EXPORT_SYMBOL_GPL(xenbus_map_ring);
>
> @@ -579,14 +723,15 @@ EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
>   static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
>   {
>   	struct xenbus_map_node *node;
> -	struct gnttab_unmap_grant_ref op = {
> -		.host_addr = (unsigned long)vaddr,
> -	};
> +	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_PAGES];
>   	unsigned int level;
> +	int i;
> +	bool leaked = false;
> +	int err;
>
>   	spin_lock(&xenbus_valloc_lock);
>   	list_for_each_entry(node, &xenbus_valloc_pages, next) {
> -		if (node->area->addr == vaddr) {
> +		if (node->pv.area->addr == vaddr) {
>   			list_del(&node->next);
>   			goto found;
>   		}
> @@ -601,22 +746,41 @@ static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
>   		return GNTST_bad_virt_addr;
>   	}
>
> -	op.handle = node->handle;
> -	op.host_addr = arbitrary_virt_to_machine(
> -		lookup_address((unsigned long)vaddr, &level)).maddr;
> +	for (i = 0; i < node->nr_handles; i++) {
> +		unsigned long addr;
> +
> +		memset(&unmap[i], 0, sizeof(unmap[i]));
> +		addr = (unsigned long)vaddr + (PAGE_SIZE * i);
> +		unmap[i].host_addr = arbitrary_virt_to_machine(
> +			lookup_address(addr, &level)).maddr;
> +		unmap[i].dev_bus_addr = 0;
> +		unmap[i].handle = node->handles[i];
> +	}
>
> -	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
> +	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
>   		BUG();
>
> -	if (op.status == GNTST_okay)
> -		free_vm_area(node->area);
> +	err = GNTST_okay;
> +	leaked = false;
> +	for (i = 0; i < node->nr_handles; i++) {
> +		if (unmap[i].status != GNTST_okay) {
> +			leaked = true;
> +			xenbus_dev_error(dev, unmap[i].status,
> +					 "unmapping page at handle %d error %d",
> +					 node->handles[i], unmap[i].status);
> +			err = unmap[i].status;
> +			break;
> +		}
> +	}
> +
> +	if (!leaked)
> +		free_vm_area(node->pv.area);
>   	else
> -		xenbus_dev_error(dev, op.status,
> -				 "unmapping page at handle %d error %d",
> -				 node->handle, op.status);
> +		pr_alert("leaking VM area %p size %u page(s)",
> +			 node->pv.area, node->nr_handles);
>
>   	kfree(node);
> -	return op.status;
> +	return err;
>   }
>
>   static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
> @@ -624,10 +788,12 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
>   	int rv;
>   	struct xenbus_map_node *node;
>   	void *addr;
> +	unsigned long addrs[XENBUS_MAX_RING_PAGES];
> +	int i;
>
>   	spin_lock(&xenbus_valloc_lock);
>   	list_for_each_entry(node, &xenbus_valloc_pages, next) {
> -		addr = pfn_to_kaddr(page_to_pfn(node->page));
> +		addr = node->hvm.addr;
>   		if (addr == vaddr) {
>   			list_del(&node->next);
>   			goto found;
> @@ -643,12 +809,16 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
>   		return GNTST_bad_virt_addr;
>   	}
>
> -	rv = xenbus_unmap_ring(dev, node->handle, addr);
> +	for (i = 0; i < node->nr_handles; i++)
> +		addrs[i] = (unsigned long)pfn_to_kaddr(page_to_pfn(node->hvm.pages[i]));
>
> +	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
> +			       addrs);
>   	if (!rv)
> -		free_xenballooned_pages(1, &node->page);
> +		vunmap(vaddr);
>   	else
> -		WARN(1, "Leaking %p\n", vaddr);
> +		WARN(1, "Leaking %p, size %u page(s)\n", vaddr,
> +		     node->nr_handles);
>
>   	kfree(node);
>   	return rv;
> @@ -657,29 +827,44 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
>   /**
>    * xenbus_unmap_ring
>    * @dev: xenbus device
> - * @handle: grant handle
> - * @vaddr: addr to unmap
> + * @handles: grant handle array
> + * @nr_handles: number of handles in the array
> + * @vaddrs: addresses to unmap
>    *
> - * Unmap a page of memory in this domain that was imported from another domain.
> + * Unmap memory in this domain that was imported from another domain.
>    * Returns 0 on success and returns GNTST_* on error
>    * (see xen/include/interface/grant_table.h).
>    */
>   int xenbus_unmap_ring(struct xenbus_device *dev,
> -		      grant_handle_t handle, void *vaddr)
> +		      grant_handle_t *handles, unsigned int nr_handles,
> +		      unsigned long *vaddrs)
>   {
> -	struct gnttab_unmap_grant_ref op;
> +	struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_PAGES];
> +	int i;
> +	int err;
>
> -	gnttab_set_unmap_op(&op, (unsigned long)vaddr, GNTMAP_host_map, handle);
> +	if (nr_handles > XENBUS_MAX_RING_PAGES)
> +		return -EINVAL;
>
> -	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
> +	for (i = 0; i < nr_handles; i++)
> +		gnttab_set_unmap_op(&unmap[i], vaddrs[i],
> +				    GNTMAP_host_map, handles[i]);
> +
> +	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
>   		BUG();
>
> -	if (op.status != GNTST_okay)
> -		xenbus_dev_error(dev, op.status,
> -				 "unmapping page at handle %d error %d",
> -				 handle, op.status);
> +	err = GNTST_okay;
> +	for (i = 0; i < nr_handles; i++) {
> +		if (unmap[i].status != GNTST_okay) {
> +			xenbus_dev_error(dev, unmap[i].status,
> +					 "unmapping page at handle %d error %d",
> +					 handles[i], unmap[i].status);
> +			err = unmap[i].status;
> +			break;
> +		}
> +	}
>
> -	return op.status;
> +	return err;
>   }
>   EXPORT_SYMBOL_GPL(xenbus_unmap_ring);
>
> diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
> index b0f1c9e..289c0b5 100644
> --- a/include/xen/xenbus.h
> +++ b/include/xen/xenbus.h
> @@ -46,6 +46,10 @@
>   #include <xen/interface/io/xenbus.h>
>   #include <xen/interface/io/xs_wire.h>
>
> +#define XENBUS_MAX_RING_PAGE_ORDER 4
> +#define XENBUS_MAX_RING_PAGES      (1U << XENBUS_MAX_RING_PAGE_ORDER)
> +#define INVALID_GRANT_HANDLE       (~0U)
> +
>   /* Register callback to watch this node. */
>   struct xenbus_watch
>   {
> @@ -199,15 +203,19 @@ int xenbus_watch_pathfmt(struct xenbus_device *dev, struct xenbus_watch *watch,
>   			 const char *pathfmt, ...);
>
>   int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state new_state);
> -int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn);
> -int xenbus_map_ring_valloc(struct xenbus_device *dev,
> -			   int gnt_ref, void **vaddr);
> -int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
> -			   grant_handle_t *handle, void *vaddr);
> +int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
> +		      unsigned int nr_pages, grant_ref_t *grefs);
> +int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
> +			   unsigned int nr_grefs, void **vaddr);
> +int xenbus_map_ring(struct xenbus_device *dev,
> +		    grant_ref_t *gnt_refs, unsigned int nr_grefs,
> +		    grant_handle_t *handles, unsigned long *vaddrs,
> +		    bool *leaked);
>
>   int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr);
>   int xenbus_unmap_ring(struct xenbus_device *dev,
> -		      grant_handle_t handle, void *vaddr);
> +		      grant_handle_t *handles, unsigned int nr_handles,
> +		      unsigned long *vaddrs);
>
>   int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port);
>   int xenbus_free_evtchn(struct xenbus_device *dev, int port);
>

Re: [PATCH 2/3] blkif: enable multi-page ring supporting

[David Vrabel]

On 03/04/15 07:45, Bob Liu wrote:
> Remove the 'DEPRECATED' and next patch will follow the protocol defined here to
> support multi-page ring.

Why are you un-deprecating this instead of using max-ring-page-order?
Are you allowing for non power of two counts? If so, the documentation
needs to be updated as well.

Also num-ring-pages is also tagged as deprecated.

Changes in blkif.h need to be made in Xen first.

David

> --- a/xen/include/public/io/blkif.h
> +++ b/xen/include/public/io/blkif.h
> @@ -303,7 +303,7 @@
>   *      Values:         <uint32_t>
>   *      Default Value:  1
>   *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
> - *      Notes:          DEPRECATED, 2, 3
> + *      Notes:          2, 3
>   *
>   *      The size of the frontend allocated request ring buffer in units of
>   *      machine pages.  The value must be a power of 2.
> 

Re: [PATCH v6 1/3] xenbus_client: Extend interface to support multi-page ring

[David Vrabel]

On 03/04/15 07:44, Bob Liu wrote:
> From: Wei Liu <wei.liu2@citrix.com>
> 
> Originally Xen PV drivers only use single-page ring to pass along
> information. This might limit the throughput between frontend and
> backend.
> 
> The patch extends Xenbus driver to support multi-page ring, which in
> general should improve throughput if ring is the bottleneck. Changes to
> various frontend / backend to adapt to the new interface are also
> included.
> 
> Affected Xen drivers:
> * blkfront/back
> * netfront/back
> * pcifront/back
> * scsifront/back
> 
> The interface is documented, as before, in xenbus_client.c.

Applied to devel/for-linus-4.1 in the expectation that a user of the new
API is be ready shortly.

> Change in V2:

Please but changes after a --- separator in future.

David

Re: [PATCH 2/3] blkif: enable multi-page ring supporting

[Konrad Rzeszutek Wilk]

On Wed, Apr 08, 2015 at 11:46:44AM +0100, David Vrabel wrote:
> On 03/04/15 07:45, Bob Liu wrote:
> > Remove the 'DEPRECATED' and next patch will follow the protocol defined here to
> > support multi-page ring.
> 
> Why are you un-deprecating this instead of using max-ring-page-order?
> Are you allowing for non power of two counts? If so, the documentation
> needs to be updated as well.
> 
> Also num-ring-pages is also tagged as deprecated.
> 
> Changes in blkif.h need to be made in Xen first.

Um, this patch is against Xen tree.

> 
> David
> 
> > --- a/xen/include/public/io/blkif.h
> > +++ b/xen/include/public/io/blkif.h
> > @@ -303,7 +303,7 @@
> >   *      Values:         <uint32_t>
> >   *      Default Value:  1
> >   *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
> > - *      Notes:          DEPRECATED, 2, 3
> > + *      Notes:          2, 3
> >   *
> >   *      The size of the frontend allocated request ring buffer in units of
> >   *      machine pages.  The value must be a power of 2.
> > 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [PATCH 2/3] blkif: enable multi-page ring supporting

[David Vrabel]

On 08/04/15 15:21, Konrad Rzeszutek Wilk wrote:
> On Wed, Apr 08, 2015 at 11:46:44AM +0100, David Vrabel wrote:
>> On 03/04/15 07:45, Bob Liu wrote:
>>> Remove the 'DEPRECATED' and next patch will follow the protocol defined here to
>>> support multi-page ring.
>>
>> Why are you un-deprecating this instead of using max-ring-page-order?
>> Are you allowing for non power of two counts? If so, the documentation
>> needs to be updated as well.
>>
>> Also num-ring-pages is also tagged as deprecated.
>>
>> Changes in blkif.h need to be made in Xen first.
> 
> Um, this patch is against Xen tree.

With this being patch #2 in a Linux series no one else is going to
notice this is Xen patch either.

David

>>> --- a/xen/include/public/io/blkif.h
>>> +++ b/xen/include/public/io/blkif.h
>>> @@ -303,7 +303,7 @@
>>>   *      Values:         <uint32_t>
>>>   *      Default Value:  1
>>>   *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
>>> - *      Notes:          DEPRECATED, 2, 3
>>> + *      Notes:          2, 3
>>>   *
>>>   *      The size of the frontend allocated request ring buffer in units of
>>>   *      machine pages.  The value must be a power of 2.
>>>
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org
>> http://lists.xen.org/xen-devel

Re: [PATCH 2/3] blkif: enable multi-page ring supporting

[Bob Liu]

On 04/08/2015 10:25 PM, David Vrabel wrote:
> On 08/04/15 15:21, Konrad Rzeszutek Wilk wrote:
>> On Wed, Apr 08, 2015 at 11:46:44AM +0100, David Vrabel wrote:
>>> On 03/04/15 07:45, Bob Liu wrote:
>>>> Remove the 'DEPRECATED' and next patch will follow the protocol defined here to
>>>> support multi-page ring.
>>>
>>> Why are you un-deprecating this instead of using max-ring-page-order?
>>> Are you allowing for non power of two counts? If so, the documentation
>>> needs to be updated as well.
>>>
>>> Also num-ring-pages is also tagged as deprecated.
>>>
>>> Changes in blkif.h need to be made in Xen first.
>>
>> Um, this patch is against Xen tree.
> 
> With this being patch #2 in a Linux series no one else is going to
> notice this is Xen patch either.
> 

Sorry, I'll separate this one.

Could you please also review the [PATCH v3 3/3] xen/block: add
multi-page ring support?

Thanks,
-Bob