在 2022/3/3 上午2:23, Eugenio Perez Martin 写道:
+
+static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
+ VirtQueueElement *elem,
+ unsigned *head)
+{
+ unsigned avail_idx;
+ vring_avail_t *avail = svq->vring.avail;
+
+ *head = svq->free_head;
+
+ /* We need some descriptors here */
+ if (unlikely(!elem->out_num && !elem->in_num)) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "Guest provided element with no descriptors");
+ return false;
+ }
+
+ vhost_vring_write_descs(svq, elem->out_sg, elem->out_num,
+ elem->in_num > 0, false);
+ vhost_vring_write_descs(svq, elem->in_sg, elem->in_num, false, true);
I wonder instead of passing in/out separately and using the hint like
more_descs, is it better to simply pass the elem to
vhost_vrign_write_descs() then we know which one is the last that
doesn't depend on more_descs.
I'm not sure I follow this.
The purpose of vhost_vring_write_descs is to abstract the writing of a
batch of descriptors, its chaining, etc. It accepts the write
parameter just for the write flag. If we make elem as a parameter, we
would need to duplicate that for loop for read and for write
descriptors, isn't it?
To duplicate the for loop is the way it is done in the kernel, but I
actually think the kernel could benefit from abstracting both in the
same function too. Please let me know if you think otherwise or I've
missed your point.
Ok, so it's just a suggestion and we can do optimization on top for sure.
Thanks
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