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>
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@@ -714,6 +714,7 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
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{
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struct xenbus_device *dev = info->dev;
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struct vscsiif_sring *sring;
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grant_ref_t gref;
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int err = -ENOMEM;
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/***** Frontend to Backend ring start *****/
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@@ -726,14 +727,14 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
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SHARED_RING_INIT(sring);
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FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
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err = xenbus_grant_ring(dev, virt_to_mfn(sring));
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err = xenbus_grant_ring(dev, sring, 1, &gref);
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if (err < 0) {
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free_page((unsigned long)sring);
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xenbus_dev_fatal(dev, err,
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"fail to grant shared ring (Front to Back)");
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return err;
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}
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info->ring_ref = err;
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info->ring_ref = gref;
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err = xenbus_alloc_evtchn(dev, &info->evtchn);
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if (err) {
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