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virtio_ring: factor out core logic for updating last_used_idx

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Factor out the core logic for updating last_used_idx to be reused by
the packed in order implementation.

Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-17-jasowang@redhat.com>
This commit is contained in:
Jason Wang
2025-12-30 14:46:46 +08:00
committed by Michael S. Tsirkin
parent c623106c79
commit fa56d17b92
1 changed files with 25 additions and 18 deletions
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43
drivers/virtio/virtio_ring.c
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@@ -1754,6 +1754,30 @@ static bool more_used_packed(const struct vring_virtqueue *vq)
return virtqueue_poll_packed(vq, READ_ONCE(vq->last_used_idx));
}
static void update_last_used_idx_packed(struct vring_virtqueue *vq,
u16 id, u16 last_used,
u16 used_wrap_counter)
{
last_used += vq->packed.desc_state[id].num;
if (unlikely(last_used >= vq->packed.vring.num)) {
last_used -= vq->packed.vring.num;
used_wrap_counter ^= 1;
}
last_used = (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRAP_CTR));
WRITE_ONCE(vq->last_used_idx, last_used);
/*
* If we expect an interrupt for the next entry, tell host
* by writing event index and flush out the write before
* the read in the next get_buf call.
*/
if (vq->packed.event_flags_shadow == VRING_PACKED_EVENT_FLAG_DESC)
virtio_store_mb(vq->weak_barriers,
&vq->packed.vring.driver->off_wrap,
cpu_to_le16(vq->last_used_idx));
}
static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq,
unsigned int *len,
void **ctx)
@@ -1797,24 +1821,7 @@ static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq,
ret = vq->packed.desc_state[id].data;
detach_buf_packed(vq, id, ctx);
last_used += vq->packed.desc_state[id].num;
if (unlikely(last_used >= vq->packed.vring.num)) {
last_used -= vq->packed.vring.num;
used_wrap_counter ^= 1;
}
last_used = (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRAP_CTR));
WRITE_ONCE(vq->last_used_idx, last_used);
/*
* If we expect an interrupt for the next entry, tell host
* by writing event index and flush out the write before
* the read in the next get_buf call.
*/
if (vq->packed.event_flags_shadow == VRING_PACKED_EVENT_FLAG_DESC)
virtio_store_mb(vq->weak_barriers,
&vq->packed.vring.driver->off_wrap,
cpu_to_le16(vq->last_used_idx));
update_last_used_idx_packed(vq, id, last_used, used_wrap_counter);
LAST_ADD_TIME_INVALID(vq);