On 2018年10月11日 22:08, w...@redhat.com wrote:
From: Wei Xu <w...@redhat.com>
Same thought as 1.0 except a bit confused when trying to reuse
'shadow_avail_idx', so the interrelated new event_idx and the wrap
counter for notifications has been introduced in previous patch.
Signed-off-by: Wei Xu <w...@redhat.com>
---
hw/virtio/virtio.c | 176 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 173 insertions(+), 3 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 86f88da..13c6c98 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -375,6 +375,17 @@ int virtio_queue_ready(VirtQueue *vq)
return vq->vring.avail != 0;
}
+static void vring_packed_desc_read(VirtIODevice *vdev, VRingPackedDesc *desc,
+ MemoryRegionCache *cache, int i)
+{
+ address_space_read_cached(cache, i * sizeof(VRingPackedDesc),
+ desc, sizeof(VRingPackedDesc));
+ virtio_tswap16s(vdev, &desc->flags);
+ virtio_tswap64s(vdev, &desc->addr);
+ virtio_tswap32s(vdev, &desc->len);
+ virtio_tswap16s(vdev, &desc->id);
+}
+
static void vring_packed_desc_read_flags(VirtIODevice *vdev,
VRingPackedDesc *desc, MemoryRegionCache *cache, int i)
{
@@ -672,9 +683,9 @@ static int virtqueue_read_next_desc(VirtIODevice *vdev,
VRingDesc *desc,
return VIRTQUEUE_READ_DESC_MORE;
}
-void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
- unsigned int *out_bytes,
- unsigned max_in_bytes, unsigned max_out_bytes)
+static void virtqueue_split_get_avail_bytes(VirtQueue *vq,
+ unsigned int *in_bytes, unsigned int *out_bytes,
+ unsigned max_in_bytes, unsigned max_out_bytes)
{
VirtIODevice *vdev = vq->vdev;
unsigned int max, idx;
@@ -797,6 +808,165 @@ err:
goto done;
}
+static void virtqueue_packed_get_avail_bytes(VirtQueue *vq,
+ unsigned int *in_bytes, unsigned int *out_bytes,
+ unsigned max_in_bytes, unsigned max_out_bytes)
+{
+ VirtIODevice *vdev = vq->vdev;
+ unsigned int max, idx;
+ unsigned int total_bufs, in_total, out_total;
+ MemoryRegionCache *desc_cache;
+ VRingMemoryRegionCaches *caches;
+ MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
+ int64_t len = 0;
+ VRingPackedDesc desc;
+ bool wrap_counter;
+
+ if (unlikely(!vq->vring.desc)) {
+ if (in_bytes) {
+ *in_bytes = 0;
+ }
+ if (out_bytes) {
+ *out_bytes = 0;
+ }
+ return;
+ }
+
+ rcu_read_lock();
+ idx = vq->last_avail_idx;
+ wrap_counter = vq->avail_wrap_counter;
+ total_bufs = in_total = out_total = 0;
+
+ max = vq->vring.num;
+ caches = vring_get_region_caches(vq);
+ if (caches->desc.len < max * sizeof(VRingPackedDesc)) {
+ virtio_error(vdev, "Cannot map descriptor ring");
+ goto err;
+ }
The above is mostly duplicated with split version. Can we unify them and
start the different version here?
+
+ desc_cache = &caches->desc;
+ vring_packed_desc_read(vdev, &desc, desc_cache, idx);
+ /* Make sure we see all the fields*/
+ smp_rmb();
This looks strange. Do you want to make sure the flags were read before
other fields of descriptor?
You probably need a helper which did:
vring_packed_desc_read_flags(&desc)
if (is_desc_avail(&desc) {
smp_rmb();
return true;
}
return false;
+ while (is_desc_avail(&desc, wrap_counter)) {
+ unsigned int num_bufs;
+ unsigned int i = 0;
+
+ num_bufs = total_bufs;
+
+ if (desc.flags & VRING_DESC_F_INDIRECT) {
+ if (desc.len % sizeof(VRingPackedDesc)) {
+ virtio_error(vdev, "Invalid size for indirect buffer table");
+ goto err;
+ }
+
+ /* If we've got too many, that implies a descriptor loop. */
+ if (num_bufs >= max) {
+ virtio_error(vdev, "Looped descriptor");
+ goto err;
+ }
+
+ /* loop over the indirect descriptor table */
+ len = address_space_cache_init(&indirect_desc_cache,
+ vdev->dma_as,
+ desc.addr, desc.len, false);
+ desc_cache = &indirect_desc_cache;
+ if (len < desc.len) {
+ virtio_error(vdev, "Cannot map indirect buffer");
+ goto err;
Do we need to destroy desc cache here?
+ }
+
+ max = desc.len / sizeof(VRingPackedDesc);
+ num_bufs = i = 0;
+ vring_packed_desc_read(vdev, &desc, desc_cache, i);
+ /* Make sure we see all the fields*/
+ smp_rmb();
All fields have already been read by us, why need this barrier?
+ }
+
+ do {
+ /* If we've got too many, that implies a descriptor loop. */
+ if (++num_bufs > max) {
+ virtio_error(vdev, "Looped descriptor");
+ goto err;
+ }
+
+ if (desc.flags & VRING_DESC_F_WRITE) {
+ in_total += desc.len;
+ } else {
+ out_total += desc.len;
+ }
+ if (in_total >= max_in_bytes && out_total >= max_out_bytes) {
+ goto done;
+ }
+
+ if (desc_cache == &indirect_desc_cache) {
+ if (++i > vq->vring.num) {
+ virtio_error(vdev, "Looped descriptor");
+ goto err;
+ }
This duplicates with the above num_bufs check I think? And it's better
to check them before the avail bytes calculation.
+ vring_packed_desc_read(vdev, &desc, desc_cache, i);
+ } else {
+ if (++idx >= vq->vring.num) {
+ idx -= vq->vring.num;
+ wrap_counter = !wrap_counter;
+ }
+ vring_packed_desc_read(vdev, &desc, desc_cache, idx);
+ }
+ /* Make sure we see the flags */
+ smp_rmb();
This is also suspicious. For commenting, we usually mention the order we
want like
"make sure XXX is read/write before YYY."
+ } while (desc.flags & VRING_DESC_F_NEXT);
Why not implement a split version of virtqueue_read_next_desc() and hide
all e.g wrap counter & barrier stuffs there?
+
+ if (desc_cache == &indirect_desc_cache) {
+ address_space_cache_destroy(&indirect_desc_cache);
+ total_bufs++;
+ /* We missed one step on for indirect desc */
+ idx++;
+ if (++idx >= vq->vring.num) {
+ idx -= vq->vring.num;
+ wrap_counter = !wrap_counter;
+ }
+ } else {
+ total_bufs = num_bufs;
+ }
+
+ desc_cache = &caches->desc;
+ vring_packed_desc_read(vdev, &desc, desc_cache, idx);
+ /* Make sure we see all the fields */
+ smp_rmb();
Need to better comment for explaining this barrier as well.
+ }
+
+ /* Set up index and wrap counter for an interrupt when no enough desc */
I don't get what did this mean?
Thanks
+ vq->event_idx = idx;
+ vq->event_wrap_counter = wrap_counter;
+done:
+ address_space_cache_destroy(&indirect_desc_cache);
+ if (in_bytes) {
+ *in_bytes = in_total;
+ }
+ if (out_bytes) {
+ *out_bytes = out_total;
+ }
+ rcu_read_unlock();
+ return;
+
+err:
+ in_total = out_total = 0;
+ goto done;
+}
+
+void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
+ unsigned int *out_bytes,
+ unsigned max_in_bytes, unsigned max_out_bytes)
+{
+ if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
+ virtqueue_packed_get_avail_bytes(vq, in_bytes, out_bytes,
+ max_in_bytes, max_out_bytes);
+ } else {
+ virtqueue_split_get_avail_bytes(vq, in_bytes, out_bytes,
+ max_in_bytes, max_out_bytes);
+ }
+}
+
int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,
unsigned int out_bytes)
{
