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[Qemu-devel] [PATCH v4 05/11] virtio: queue/descriptor check helpers for
From: |
wexu |
Subject: |
[Qemu-devel] [PATCH v4 05/11] virtio: queue/descriptor check helpers for packed ring |
Date: |
Wed, 13 Feb 2019 23:26:36 -0500 |
From: Wei Xu <address@hidden>
These are descriptor available and queue empty check helpers.
Signed-off-by: Wei Xu <address@hidden>
---
hw/virtio/virtio.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 55 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 54dc098..f2ff980 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -368,6 +368,25 @@ int virtio_queue_ready(VirtQueue *vq)
return vq->vring.avail != 0;
}
+static void vring_packed_desc_read_flags(VirtIODevice *vdev,
+ VRingPackedDesc *desc, MemoryRegionCache *cache, int i)
+{
+ address_space_read_cached(cache,
+ i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags),
+ &desc->flags, sizeof(desc->flags));
+ virtio_tswap16s(vdev, &desc->flags);
+}
+
+static inline bool is_desc_avail(struct VRingPackedDesc *desc,
+ bool wrap_counter)
+{
+ bool avail, used;
+
+ avail = !!(desc->flags & (1 << VRING_PACKED_DESC_F_AVAIL));
+ used = !!(desc->flags & (1 << VRING_PACKED_DESC_F_USED));
+ return (avail != used) && (avail == wrap_counter);
+}
+
/* Fetch avail_idx from VQ memory only when we really need to know if
* guest has added some buffers.
* Called within rcu_read_lock(). */
@@ -388,7 +407,7 @@ static int virtio_queue_empty_rcu(VirtQueue *vq)
return vring_avail_idx(vq) == vq->last_avail_idx;
}
-int virtio_queue_empty(VirtQueue *vq)
+static int virtio_queue_split_empty(VirtQueue *vq)
{
bool empty;
@@ -410,6 +429,41 @@ int virtio_queue_empty(VirtQueue *vq)
return empty;
}
+static int virtio_queue_packed_empty_rcu(VirtQueue *vq)
+{
+ struct VRingPackedDesc desc;
+ VRingMemoryRegionCaches *cache;
+
+ if (unlikely(!vq->vring.desc)) {
+ return 1;
+ }
+
+ cache = vring_get_region_caches(vq);
+ vring_packed_desc_read_flags(vq->vdev, &desc, &cache->desc,
+ vq->last_avail_idx);
+
+ return !is_desc_avail(&desc, vq->last_avail_wrap_counter);
+}
+
+static int virtio_queue_packed_empty(VirtQueue *vq)
+{
+ bool empty;
+
+ rcu_read_lock();
+ empty = virtio_queue_packed_empty_rcu(vq);
+ rcu_read_unlock();
+ return empty;
+}
+
+int virtio_queue_empty(VirtQueue *vq)
+{
+ if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
+ return virtio_queue_packed_empty(vq);
+ } else {
+ return virtio_queue_split_empty(vq);
+ }
+}
+
static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len)
{
--
1.8.3.1
- [Qemu-devel] [PATCH v4 00/11] packed ring virtio-net backends support, wexu, 2019/02/13
- [Qemu-devel] [PATCH v4 04/11] virtio: initialize wrap counter for packed ring, wexu, 2019/02/13
- [Qemu-devel] [PATCH v4 05/11] virtio: queue/descriptor check helpers for packed ring,
wexu <=
- [Qemu-devel] [PATCH v4 02/11] virtio: device/driver area size calculation helper for split ring, wexu, 2019/02/13
- [Qemu-devel] [PATCH v4 03/11] virtio: initialize packed ring region, wexu, 2019/02/13
- [Qemu-devel] [PATCH v4 01/11] virtio: rename structure for packed ring, wexu, 2019/02/13
- [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, wexu, 2019/02/13
- Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, Jason Wang, 2019/02/19
- Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, Wei Xu, 2019/02/19
- Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, Jason Wang, 2019/02/19
- Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, Wei Xu, 2019/02/19
- Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, Jason Wang, 2019/02/19
- Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly, Wei Xu, 2019/02/19