Re: [PATCH/RFC] Implement the memory_map hypercall

[Glauber de Oliveira Costa <gcosta@redhat.com>]

On Fri, Nov 24, 2006 at 11:36:36PM +0900, Jun Koi wrote:
> Glauber, what is this hypercall for? To map hypervisor memory from Dom0?

This hypercall (already declared, but currently always returning ENOSYS)
is meant to give a guest (any guest) the idea on how should this
physical memory mapping look like.

Currently, linux guest kernels checks for the result of such a call, and
stabilish a memory mapping on their own if it returns ENOSYS. However,
such mapping is not proving itself to be the most suitable one,
specially in a long term.

That said, when you boot a 300mb guest, instead of:

BIOS-provided physical RAM map:
 Xen: 0000000000000000 - 0000000013400000 (usable)

You'd see your RAM mapping being extended to whatever value 
is set in  d->memory_map_limit ( or even for some reason, in the future,
a differently organized map)


-- 
Glauber de Oliveira Costa
Red Hat Inc.
"Free as in Freedom"