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>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index e9b960f0ff32..13f5e7ff4bb5 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);