On Mon, Oct 15, 2018 at 11:18:05AM +0800, Jason Wang wrote:
>
>
> On 2018年10月11日 22:08, w...@redhat.com wrote:
> >From: Wei Xu <w...@redhat.com>
> >
> >Basic initialization and helpers for packed ring.
> >
> >Signed-off-by: Wei Xu <w...@redhat.com>
> >---
> > hw/virtio/virtio.c | 57
> > +++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 56 insertions(+), 1 deletion(-)
> >
> >diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >index 9185efb..86f88da 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
> >@@ -372,6 +375,23 @@ 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));
> >+}
> >+
> >+static inline bool is_desc_avail(struct VRingPackedDesc *desc, bool wc)
> >+{
>
> I think it's better use wrap_counter instead of wc here (unless you want to
> use wc everywhere which is a even worse idea).
It was to avoid a new line for a parameter since this is a mini function,
I will take it back.
Wei
>
> Thanks
>
> >+ bool avail, used;
> >+
> >+ avail = !!(desc->flags & AVAIL_DESC_PACKED(1));
> >+ used = !!(desc->flags & USED_DESC_PACKED(1));
> >+ return (avail != used) && (avail == wc);
> >+}
> >+
> > /* Fetch avail_idx from VQ memory only when we really need to know if
> > * guest has added some buffers.
> > * Called within rcu_read_lock(). */
> >@@ -392,7 +412,7 @@ 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;
> >@@ -414,6 +434,41 @@ 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->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)
> > {
>
