From fa56d17b9241394aaa77ee622b72a1b765a48d6e Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Tue, 30 Dec 2025 14:46:46 +0800 Subject: [PATCH] virtio_ring: factor out core logic for updating last_used_idx MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Factor out the core logic for updating last_used_idx to be reused by the packed in order implementation. Acked-by: Eugenio Pérez Reviewed-by: Xuan Zhuo Signed-off-by: Jason Wang Tested-by: Lei Yang Reviewed-by: Eugenio Pérez Signed-off-by: Michael S. Tsirkin Message-Id: <20251230064649.55597-17-jasowang@redhat.com> --- drivers/virtio/virtio_ring.c | 43 +++++++++++++++++++++--------------- 1 file changed, 25 insertions(+), 18 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 27f69859ccf37..3389aad6f5a87 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -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); -- 2.47.3