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Re: [Xen-devel] xen and cr0,cr3,cr4

To: Adam Sulmicki <adam@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] xen and cr0,cr3,cr4
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 29 Nov 2004 23:35:57 +0000
Cc: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx
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> > > All dandy and nice. now the weird part is that if I try to list Page Table
> > > entries referenced by by Page Directory in either setup I get an ooops
> > > saying that the referneced Page Table is not in memory.
> > >
> > > No such problems in linux classic... weird.
> >
> > How are you converting the address in the PDE into something you can
> > dereference? You should be using machine_to_virt() (*not*
> > phys_to_virt()).
> yeah, that definitely helps, in so far that I was able to list low
> memory, ie 0-(4gb-64), but it still seems to get confused once it gets
> into xen space...

Your Linux instance has no valid virtual address for the Xen-private
page tables (machine_to_virt() is only usable for pages of memory that
are permanently mapped into Linux's address space). In fact, Xen won't
allow any domain to map any of it's private memory, so there is no way
for you to print the PT contents from Linux, unless you hack the
mapping-checking code in Xen.

 -- Keir

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