x86: Add 64-bit entries to the GDT

At present it is not possible to execution 64-bit code without
installing an entire new Global Descriptor Table. This is inconvenient
since kvm does not seem to like switching into long mode with a new
table.

It isn't actually necessary, since we can just extend the existing
table. Add some new entries to this effect.

Signed-off-by: Simon Glass <sjg@chromium.org>
2 files changed