Currently x86-64 efi_call_phys_prolog() saves into a global variable (save_pgd),
and efi_call_phys_epilog() restores the kernel pagetables from that global
variable.
Change this to a cleaner save/restore pattern where the saving function returns
the saved object and the restore function restores that.
Apply the same concept to the 32-bit code as well.
Plus this approach, as an added bonus, allows us to express the
!efi_enabled(EFI_OLD_MEMMAP) situation in a clean fashion as well,
via a 'NULL' return value.
Cc: Tapasweni Pathak <tapaswenipathak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
744937b0b1