[Lguest] [kvm-devel] [PATCH 6/6] virtio ring helper

Rusty Russell rusty at rustcorp.com.au
Fri Sep 21 12:04:11 EST 2007


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.




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