On Thu, Jun 02, 2011 at 02:42:51PM +0300, Avi Kivity wrote: > On 06/02/2011 01:42 PM, Michael S. Tsirkin wrote: > >On Wed, Jun 01, 2011 at 05:51:54PM +0300, Avi Kivity wrote: > >> 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)? > > > >Exactly the reverse :) > > They're both equally bad. > > >> 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. > > > >Right. If there are two buffers of variable length there > >should be two add_buf calls. > > No. The guest should be free to use one large continuous buffer of > size N, of N buffers of size 1.
That's exactly what I was saying. > -- > error compiling committee.c: too many arguments to function
