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[Qemu-devel] [RFC v2 3/8] virtio: empty check and desc read for packed r
From: |
wexu |
Subject: |
[Qemu-devel] [RFC v2 3/8] virtio: empty check and desc read for packed ring |
Date: |
Tue, 5 Jun 2018 15:07:58 -0400 |
From: Wei Xu <address@hidden>
helper for ring empty check and descriptor read.
Signed-off-by: Wei Xu <address@hidden>
---
hw/virtio/virtio.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 59 insertions(+), 3 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index f6c0689..bd669a2 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -24,6 +24,9 @@
#include "hw/virtio/virtio-access.h"
#include "sysemu/dma.h"
+#define AVAIL_DESC_PACKED(b) ((b) << 7)
+#define USED_DESC_PACKED(b) ((b) << 15)
+
/*
* The alignment to use between consumer and producer parts of vring.
* x86 pagesize again. This is the default, used by transports like PCI
@@ -357,10 +360,27 @@ int virtio_queue_ready(VirtQueue *vq)
return vq->vring.avail != 0;
}
+static void vring_packed_desc_read(VirtIODevice *vdev, VRingDescPacked *desc,
+ MemoryRegionCache *cache, int i)
+{
+ address_space_read_cached(cache, i * sizeof(VRingDescPacked),
+ desc, sizeof(VRingDescPacked));
+ virtio_tswap64s(vdev, &desc->addr);
+ virtio_tswap32s(vdev, &desc->len);
+ virtio_tswap16s(vdev, &desc->id);
+ virtio_tswap16s(vdev, &desc->flags);
+}
+
+static inline bool is_desc_avail(struct VRingDescPacked *desc)
+{
+ return !!(desc->flags & AVAIL_DESC_PACKED(1)) !=
+ !!(desc->flags & USED_DESC_PACKED(1));
+}
+
/* Fetch avail_idx from VQ memory only when we really need to know if
* guest has added some buffers.
* Called within rcu_read_lock(). */
-static int virtio_queue_empty_rcu(VirtQueue *vq)
+static int virtio_queue_split_empty_rcu(VirtQueue *vq)
{
if (unlikely(!vq->vring.avail)) {
return 1;
@@ -373,7 +393,7 @@ 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;
@@ -391,6 +411,42 @@ int virtio_queue_empty(VirtQueue *vq)
return empty;
}
+static int virtio_queue_packed_empty_rcu(VirtQueue *vq)
+{
+ struct VRingDescPacked desc;
+ VRingMemoryRegionCaches *cache;
+
+ if (unlikely(!vq->vring.desc)) {
+ return 1;
+ }
+
+ cache = vring_get_region_caches(vq);
+ vring_packed_desc_read(vq->vdev, &desc, &cache->desc, vq->last_avail_idx);
+
+ /* Make sure we see the updated flag */
+ smp_mb();
+ return !is_desc_avail(&desc);
+}
+
+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)
{
@@ -862,7 +918,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
return NULL;
}
rcu_read_lock();
- if (virtio_queue_empty_rcu(vq)) {
+ if (virtio_queue_split_empty_rcu(vq)) {
goto done;
}
/* Needed after virtio_queue_empty(), see comment in
--
1.8.3.1
- [Qemu-devel] [RFC v2 0/8] packed ring virtio-net userspace backend support, wexu, 2018/06/05
- [Qemu-devel] [RFC v2 1/8] virtio: feature bit, data structure, init for 1.1, wexu, 2018/06/05
- [Qemu-devel] [RFC v2 2/8] virtio: memory cache for packed ring, wexu, 2018/06/05
- [Qemu-devel] [RFC v2 3/8] virtio: empty check and desc read for packed ring,
wexu <=
- [Qemu-devel] [RFC v2 4/8] virtio: get avail bytes check for packed ring, wexu, 2018/06/05
- [Qemu-devel] [RFC v2 5/8] virtio: queue pop for packed ring, wexu, 2018/06/05
[Qemu-devel] [RFC v2 6/8] virtio: flush/push for packed ring, wexu, 2018/06/05