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Commit 770b31a8 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Rusty Russell
Browse files

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: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent a1b38387

include/linux/virtio_ring.h

+14 −1
Original line number Diff line number Diff line
@@ -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__