[Xen-devel] question about xen virtual base address

["Agarwal, Lomesh" <lomesh.agarwal@xxxxxxxxx>]

I have two questions regarding x86_64 xen boot code -
1. It looks like Xen base virtual address is 0xFFFF830000000000. That's
why Page table needs to have mirror mapping for lower and higher virtual
address. If the base virtual address would have been 0 (__PAGE_OFFSET),
code in file x86_64.S would have been much easy to understand and
maintain. So, is there a specific reason to choose this high virtual
address?
2. Why do we need to subtract FIRST_RESERVED_GDT_BYTE (14 pages) from
address of gdt_table when calculating the base address for GDT table?
How does this subtraction give the right address for GDT table?

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