From: Wei Xu <w...@redhat.com> helper for ring empty check.
Signed-off-by: Wei Xu <w...@redhat.com> --- 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 73a35a4..478df3d 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 @@ -446,10 +449,27 @@ int virtio_queue_ready(VirtQueue *vq) return vq->vring.avail != 0; } +static void vring_desc_read_packed(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_empty_split_rcu(VirtQueue *vq) { if (unlikely(!vq->vring.avail)) { return 1; @@ -462,7 +482,7 @@ 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_empty_split(VirtQueue *vq) { bool empty; @@ -480,6 +500,42 @@ int virtio_queue_empty(VirtQueue *vq) return empty; } +static int virtio_queue_empty_packed_rcu(VirtQueue *vq) +{ + struct VRingDescPacked desc; + VRingMemoryRegionCaches *cache; + + if (unlikely(!vq->packed.desc)) { + return 1; + } + + cache = vring_get_region_caches(vq); + vring_desc_read_packed(vq->vdev, &desc, &cache->desc_packed, vq->last_avail_idx); + + /* Make sure we see the updated flag */ + smp_mb(); + return !is_desc_avail(&desc); +} + +static int virtio_queue_empty_packed(VirtQueue *vq) +{ + bool empty; + + rcu_read_lock(); + empty = virtio_queue_empty_packed_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_empty_packed(vq); + } else { + return virtio_queue_empty_split(vq); + } +} + static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len) { @@ -951,7 +1007,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) return NULL; } rcu_read_lock(); - if (virtio_queue_empty_rcu(vq)) { + if (virtio_queue_empty_split_rcu(vq)) { goto done; } /* Needed after virtio_queue_empty(), see comment in -- 2.7.4