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authorMichael S. Tsirkin <mst@redhat.com>2011-05-20 02:10:17 +0300
committerRusty Russell <rusty@rustcorp.com.au>2011-05-30 11:14:14 +0930
commit770b31a85e000b0194974922f238a30ade4246b6 (patch)
treeeed81e23f3116858b49af76bcc5831c38662de96
parenta1b383870a28cfbd1657d4922c0fafc634a62ebd (diff)
downloadop-kernel-dev-770b31a85e000b0194974922f238a30ade4246b6.zip
op-kernel-dev-770b31a85e000b0194974922f238a30ade4246b6.tar.gz
virtio: event index interface
Define a new feature bit for the guest and host to utilize an event index (like Xen) instead if a flag bit to enable/disable interrupts and kicks. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--include/linux/virtio_ring.h15
1 files changed, 14 insertions, 1 deletions
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index a813e5d..c4eef73d 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -52,6 +52,12 @@
/* We support indirect buffer descriptors */
#define VIRTIO_RING_F_INDIRECT_DESC 28
+/* The Guest publishes the used index for which it expects an interrupt
+ * at the end of the avail ring. Host should ignore the avail->flags field. */
+/* The Host publishes the avail index for which it expects a kick
+ * at the end of the used ring. Guest should ignore the used->flags field. */
+#define VIRTIO_RING_F_EVENT_IDX 29
+
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc {
/* Address (guest-physical). */
@@ -106,6 +112,7 @@ struct vring {
* __u16 avail_flags;
* __u16 avail_idx;
* __u16 available[num];
+ * __u16 used_event_idx;
*
* // Padding to the next align boundary.
* char pad[];
@@ -114,8 +121,14 @@ struct vring {
* __u16 used_flags;
* __u16 used_idx;
* struct vring_used_elem used[num];
+ * __u16 avail_event_idx;
* };
*/
+/* We publish the used event index at the end of the available ring, and vice
+ * versa. They are at the end for backwards compatibility. */
+#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
+#define vring_avail_event(vr) (*(__u16 *)&(vr)->used->ring[(vr)->num])
+
static inline void vring_init(struct vring *vr, unsigned int num, void *p,
unsigned long align)
{
@@ -130,7 +143,7 @@ static inline unsigned vring_size(unsigned int num, unsigned long align)
{
return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
+ align - 1) & ~(align - 1))
- + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
+ + sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
}
#ifdef __KERNEL__
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