There are a number of mostly older guests such as RHEL-7 which do not
support 5-level paging. This patch adds support for switching from
5-level paging mode back to 4-level paging mode. This is done in PEI,
after inspecting the address space needed (installed memory and
reservations configured via fw_cfg).
By default small guests (which need less than 1 TB) will use 4-level
paging mode. There is a fw_cfg override though, so it is possible to
force the one or the other this way:
qemu-system-x86_64 -fw_cfg name=opt/org.tianocode/PagingLevel,string=5
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Gerd Hoffmann