Re: Xen3 physical memory map/location for dom0

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Nov 09, 2006 at 02:55:48PM +1100, Daniel Carosone wrote:
> My laptop has a bce(4) onboard NIC, which annoyingly is only usable
> with DMA to physical addresses <1G.
> 
> I had hoped that, when running Xen, limiting dom0 to less than this
> quantity would be enough - but it seems that the dom0 builder
> allocates the domain's physical pages from the top down.
> 
> I haven't found any clues in xen documentation about way to alter this
> (like a flag on the xen grub commmand line).  I *can* make bce0 work
> by limiting xen to 1g of memory, but that's not really the desired
> solution longer term.
> 
> Is it something that can be influenced by the ELF headers of the dom0
> kernel?  I know there were some changes recently (as part of the 3.0.3
> support) to load addresses and other possibly promising parameters..

Actually putting a limit on dom0 memory may not be enough; a network buffer
from a domU can end up in the DMA descriptor of the network adapter

> 
> Any other clues?

How does the driver deal with this limitation ? Does it work with a plain
i386 kernel ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--