Re: [PATCH 6/6] virtio ring helper

Rusty Russell
2007-09-21T02:04:11Z

On Thu, 2007-09-20 at 14:43 +0200, Avi Kivity wrote:
> Rusty Russell wrote:
> > These helper routines supply most of the virtqueue_ops for hypervisors
> > which want to use a ring for virtio. Unlike the previous lguest
> > implementation:
> >
> > 3) The page numbers are always 64 bit (PAE anyone?)
> >
>
> 32 bits of page numbers give 44 bits of physical address on x86. That's
> 16TB per guest. Admittedly it's smaller on a VAX.

I like to feel that I make these mistakes to ensure others are paying
attention. However, it does mean that I can just put an address in
there and increase the length field to 32 bits. Much rejoicing.

Will fix and resend tomorrow (Friday is in-office-away-from-test-machine
day).

> I don't like the chaining and would prefer the descriptor to refer to an
> array of page descriptors. However I can't complain since this isn't
> common code.

The intent is for kvm to use it. I'll certainly consider your patches,
although I suspect that managing descriptor pages will make things ugly
enough to cause you to reconsider.

Thanks!
Rusty.