virtio: Don't use PAGE_SIZE in virtio_pci.c
The virtio PCI devices don't depend on the guest page size. This matters
now PowerPC virtio is gaining ground (they like 64k pages).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/virtio_pci.h b/include/linux/virtio_pci.h
index cdef357..e13d7eb 100644
--- a/include/linux/virtio_pci.h
+++ b/include/linux/virtio_pci.h
@@ -53,4 +53,8 @@
/* Virtio ABI version, this must match exactly */
#define VIRTIO_PCI_ABI_VERSION 0
+
+/* 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
#endif