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Re: [Xen-devel] Updating built-in GDT

On 24 Jan 2006, at 14:48, Ivan Kelly wrote:

You can't update the built-in GDT. Instead, create your own and pass
the list of MFNs that comprise your GDT to the set_gdt() hypercall. You
must ensure you have only read-only mappings of those MFNs before
passing them to that hypercall! If you wish to update your GDT, use the
update_descriptor() hypercall.
does set_gdt add the default descriptors(at 819, 820, 821 etc) or will i have
to insert these into my new gdt manually?

The default selectors are 0xe000 and above. They are always available, even if you install your own GDT. To achieve this trick, guest GDTs are limited to 14 pages (7168 entries) rather than 16 pages (8192 entries).

 -- Keir

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