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

On 23 Jan 2006, at 18:02, Ivan Kelly wrote:

When porting a new OS to xen (using 2.0.7) is it possible to use the builtin GDT for all your purposes, or do you have to create a new one if you want to work with anything but the descriptors that are already in the xen provided
If you can use the builtin one, how do you access the GDT? Is it in the 64M
reserved address space?

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.

We could emulate write accesses to the guest GDT, but that hasn't so far been implemented.

 -- Keir

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