On Thu, Sep 12, 2013 at 05:59:11PM +0200, Stefan Hajnoczi wrote:
> On Wed, Sep 11, 2013 at 05:46:39PM +0300, Michael S. Tsirkin wrote:
> > diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
> > index fcd9fd7..9a40973 100644
> > --- a/virtio-v1.0-wd01-part1-specification.txt
> > +++ b/virtio-v1.0-wd01-part1-specification.txt
> > @@ -223,6 +223,45 @@ transmit and one for receive. Each queue has a 16-bit queue size
> > parameter, which sets the number of entries and implies the total size
> > of the queue.
> >
> > +Each virtqueue consists of three parts:
> > +
> > + Descriptor Table
> > + Available Ring
> > + Used Ring
> > +
> > +where each part is physically-contiguous in guest memory,
> > +and has different alignment requirements.
> > +
> > +The Queue Size field controls the total number of bytes
> > +required for each part of the virtqueue.
>
> I'm lost here because I don't know where the Queue Size field comes
> from. I think the table needs to be shown first, then the explanation
> can be given:
>
> ...table...
>
> The Size column gives the total number of bytes required for each part
> of the virtqueue.
No, Queue Size is qsz = number of buffers. It has nothing to do
with the number of bytes.
> > +
> > +The memory aligment and size requirements, in bytes, of each part of the
> > +virtqueue are summarized in the following table (qsz is the Queue Size field):
>
> Perhaps it's clearer to say:
>
> qsz is the maximum number of buffers. For example, if qsz is 4 then at
> most 4 buffers can be transferred at any given time.
Exactly. So I'll put this text where the Queue Size is used first
then it'll be clear.
> > @@ -814,9 +852,11 @@ This is done as follows, for each virtqueue a device has:
> > always a power of 2. This controls how big the virtqueue is
> > (see "2.1.4. Virtqueues"). If this field is 0, the virtqueue does not exist.
> >
> > -3. Allocate and zero virtqueue in contiguous physical memory, on
> > - a 4096 byte alignment. Write the physical address, divided by
> > - 4096 to the Queue Address field.[6]
> > +3. Optionally, select a smaller virtqueue size and write it in the Queue Size
> > + field.
>
> 3...
>
> > +3. Allocate and zero Descriptor Table, Available and Used rings for the
> > + virtqueue in contiguous physical memory.
>
> ...and 3. Should this list be renumbered?
Right :)
