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Re: [Xen-devel] Is machine_to_phys_mapping a 4MB 'superpage'?

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Is machine_to_phys_mapping a 4MB 'superpage'?
From: Jacob Gorm Hansen <jacobg@xxxxxxx>
Date: Thu, 31 Mar 2005 00:47:52 -0800
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Keir Fraser wrote:

On 31 Mar 2005, at 04:25, Jacob Gorm Hansen wrote:

The machine_to_phys_mapping table is mapped permanently at 0xFC000000 (on x86-32). I would like to experiment with letting the domU map it at other locations in its virtual address space, but I suppose that for performance it is mapped as a 4MB 'super' page, and as such needs special treatment, is this correct?

It doesn't *have* to be mapped as a superpage -- control tools don't when doing suspend/resume, for example. Fixing the permission checking so that other than domain0 can remap the m2p table shouldn't be very hard, but I'm not sure what the cleanest method would be.

actually I would just like for domUs to be able to map it in different locations, in order to get a little more flexible memory layout.

I will probably just try and hack something up for my immediate needs.


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