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>
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@ -52,6 +52,12 @@
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/* We support indirect buffer descriptors */
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#define VIRTIO_RING_F_INDIRECT_DESC 28
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/* The Guest publishes the used index for which it expects an interrupt
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* at the end of the avail ring. Host should ignore the avail->flags field. */
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/* The Host publishes the avail index for which it expects a kick
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* at the end of the used ring. Guest should ignore the used->flags field. */
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#define VIRTIO_RING_F_EVENT_IDX 29
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/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
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struct vring_desc {
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/* Address (guest-physical). */
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@ -106,6 +112,7 @@ struct vring {
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* __u16 avail_flags;
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* __u16 avail_idx;
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* __u16 available[num];
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* __u16 used_event_idx;
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*
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* // Padding to the next align boundary.
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* char pad[];
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@ -114,8 +121,14 @@ struct vring {
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* __u16 used_flags;
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* __u16 used_idx;
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* struct vring_used_elem used[num];
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* __u16 avail_event_idx;
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* };
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*/
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/* We publish the used event index at the end of the available ring, and vice
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* versa. They are at the end for backwards compatibility. */
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#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
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#define vring_avail_event(vr) (*(__u16 *)&(vr)->used->ring[(vr)->num])
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static inline void vring_init(struct vring *vr, unsigned int num, void *p,
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unsigned long align)
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{
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@ -130,7 +143,7 @@ static inline unsigned vring_size(unsigned int num, unsigned long align)
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{
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return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
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+ align - 1) & ~(align - 1))
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+ sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
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+ sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
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}
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#ifdef __KERNEL__
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