Re: Xen at scale

[Kip Macy <kmacy@fsmware.com>]

On Wed, 24 Mar 2004, Christian Limpach wrote:

> > > and where does the builder put the PTD?  and what's the physical memory
> > > layout?
> >
> > For BSD both are irrelevant - the PTD is passed in as an argument via a
> > register. Only Linux relies on physical contiguity for the PTOV trick.
> > BSD does a table lookup in the mapped page tables - it has no physical
> > contiguity requirements.
>
> The domain builder still has to put the PTD somewhere and your
> drawing/explanation doesn't say where.  Same goes for physical memory
> layout, you have to pick one, I'd be interested to know which you picked...

The PTD is an arbitrary physical address mapped in right after the pages
uses by the elf-loader. BSD's VM system is sufficiently general that it
doesn't care about physical layout. Nonetheless, the physical layout
ends up looking something like:

|ktext|KPTphys|IdlePTD|ptomptpa|tmpstk|startinfopa|ptompages| <inited by kernel>

I hadn't intended to commit the domain builder until the ports had been
committed to the BSDs CVS repositories - which is going to wait until
I've had time to write the block and bi-directional console drivers.
However, if it is still unclear I can post the domain builder source
itself.



			-Kip


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