Re: [Xen-devel] doubt on domU segment mappings

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>]

Sandesh, le Mon 21 Jul 2008 23:06:31 +0530, a écrit :
> On Mon, 2008-07-21 at 18:08 +0100, Samuel Thibault wrote:
> > > or at least the pt_base mapping.
> > 
> > Well the problem is that the domU most probably has destroyed it
> > completely already.
> can't i preserve them, at least the base pointers??? :)
> can u just point to me where these segment mappings are recreated in
> domU(linux 2.6.18.1).

Linux domU starts in head-xen.S's startup_32, which calls start_kernel,
which itself becomes the idle thread, so I guess it actually preserves
it.  As for the pt_base address, you can get it from linux itself from
the xen_start_info structure.  There is no way to get that from other
domains.

> > > > Again, dom0 doesn't map them any more, it doesn't need them any
> > more.
> > > then how will the domU kernel memory is accessed? are they mapped to
> > the
> > > domU pg_tables?
> so even pt_base becomes invalid once domU has booted?? 

DomU is free to do so, yes.

Samuel

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