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Re: [Xen-devel] x86-64's paging_init()

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] x86-64's paging_init()
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 01 Sep 2006 16:49:33 +0100
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On 1/9/06 4:38 pm, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> Correct. I suggest either a clean BUG_ON() in virt_to_xen_l2e(), or
>> allocate-and-map the new l2 in that same function (but raises question of
>> how to test the new code path).
> Why in virt_to_xen_l2e()? We likely wouldn't make it there on a system
> this big, due to earlier memory corruption.

Why? The memory is only discovered and mapped after the e820 map is parsed.
The mapping occurs via map_pages_to_xen(). That function discovers the l2e
by using virt_to_xen_l2e(). So I think it ought to work.

You can test it out by doing a map_pages_to_xen() call on an area of virtual
address space that currently has no l2e. Should crash now, and work with the
modified virt_to_xen_l2e().

 -- Keir

> But anyway, I'll try to change the code so the code path won't be entirely
> unused (similar to the dom0 page table setup in contruct_dom0()).

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