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Re: [Xen-devel] pickle_domptr and unpickle_domptr issue with >4GB

To: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
Subject: Re: [Xen-devel] pickle_domptr and unpickle_domptr issue with >4GB
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 22 Jun 2005 18:36:53 +0100
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On 22 Jun 2005, at 16:56, Nakajima, Jun wrote:

__pa(domain) will be truncated (and be set to that pfn as the owner)
when we have physical pages >4GB, and unpickle_domptr will return a
wrong address. Then get_page(), for example, checks if the domain is the
ownwer for the page like (=>), and it fails...:

The Xen heap allocator (from which domain structs are taken) is limited to the bottom few megabytes of physmem. So you will never have a domain struct whose phys address overflows 32 bits.

Longer term I'd like to relax the restriction on Xen heap allocations on x86/64 so that most of physmem can be shared between Xen and domain heap allocators. At that point we'll just have to ensure that Xen allocations, or at least domain-struct allocations, only occur from bottom 4GB of memory map. Not very onerous I believe. :-)

 -- Keir

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