xenbus_client: Extend interface to support multi-page ring

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
* vtpmfront

The interface is documented, as before, in xenbus_client.c.
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: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

drivers/block/xen-blkback/xenbus.c

@@ -193,7 +193,7 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 	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;
 

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)

drivers/char/tpm/xen-tpmfront.c

@@ -193,6 +193,7 @@ static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
 	struct xenbus_transaction xbt;
 	const char *message = NULL;
 	int rv;
+	grant_ref_t gref;
 
 	priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
 	if (!priv->shr) {
@@ -200,11 +201,11 @@ static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
 		return -ENOMEM;
 	}
 
-	rv = xenbus_grant_ring(dev, virt_to_mfn(priv->shr));
+	rv = xenbus_grant_ring(dev, &priv->shr, 1, &gref);
 	if (rv < 0)
 		return rv;
 
-	priv->ring_ref = rv;
+	priv->ring_ref = gref;
 
 	rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
 	if (rv)

drivers/net/xen-netback/netback.c

@@ -1781,7 +1781,7 @@ 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;
 
@@ -1789,7 +1789,7 @@ 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;
 

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);

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)

drivers/scsi/xen-scsifront.c

@@ -714,6 +714,7 @@ 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 *****/
@@ -726,14 +727,14 @@ 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) {

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.");

drivers/xen/xen-scsiback.c

@@ -809,7 +809,7 @@ 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;
 

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);