virtio: Don't use PAGE_SIZE for vring alignment in virtio_pci.

That doesn't work for non-4k guests which are now appearing.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 drivers/virtio/virtio_pci.c |    5 +++--
 include/linux/virtio_pci.h  |    4 ++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff -r c6f6a3ab173b drivers/virtio/virtio_pci.c
--- a/drivers/virtio/virtio_pci.c	Wed Nov 12 21:51:09 2008 +1030
+++ b/drivers/virtio/virtio_pci.c	Wed Nov 12 21:57:25 2008 +1030
@@ -216,7 +216,7 @@
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	struct virtio_pci_vq_info *info;
 	struct virtqueue *vq;
-	unsigned long flags;
+	unsigned long flags, size;
 	u16 num;
 	int err;
 
@@ -237,7 +237,8 @@
 	info->queue_index = index;
 	info->num = num;
 
-	info->queue = kzalloc(PAGE_ALIGN(vring_size(num,PAGE_SIZE)), GFP_KERNEL);
+	size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
+	info->queue = kzalloc(size, GFP_KERNEL);
 	if (info->queue == NULL) {
 		err = -ENOMEM;
 		goto out_info;
diff -r c6f6a3ab173b include/linux/virtio_pci.h
--- a/include/linux/virtio_pci.h	Wed Nov 12 21:51:09 2008 +1030
+++ b/include/linux/virtio_pci.h	Wed Nov 12 21:57:25 2008 +1030
@@ -57,4 +57,8 @@
 /* How many bits to shift physical queue address written to QUEUE_PFN.
  * 12 is historical, and due to x86 page size. */
 #define VIRTIO_PCI_QUEUE_ADDR_SHIFT	12
+
+/* The alignment to use between consumer and producer parts of vring.
+ * x86 pagesize again. */
+#define VIRTIO_PCI_VRING_ALIGN		4096
 #endif