Re: [Qemu-devel] virtio scsi host draft specification, v2

[Avi Kivity]

On 06/01/2011 05:36 PM, Michael S. Tsirkin wrote:
> >
> >  So, if I am going to give this liberty with buffers to the driver, I
> >  _have_ to keep the size information.  Otherwise, I agree that it is
> >  redundant and I will remove it.  What poison do you prefer?
> >
>
> Ah, I think I understand now. Both sense and data have in
> fields that might only be used partially?
> In that case I think I agree: it's best to require the use of separate
> buffers for them, in this way used len will give you useful information
> and you won't need sense_len and data_len: just a flag to
> mark the fact that there *is* a sense buffer following.
> And the num field does that.


Do you mean to use the virtio iovec length to determine information 
about the message (like splitting it into buffers)?

I think that's a bad idea.  Splitting into buffers is a function of 
memory management.  For example, a driver in userspace (or a nested 
guest) will have additional fragmentation into 4K pages after it passes 
through the iommu.

Let's not mix layers here.

--
error compiling committee.c: too many arguments to function