[PATCH 5/5] Documentation/x86: Update EFI memory region description

From: Matt Fleming
Date: Sat Nov 14 2015 - 17:02:14 EST

Make it clear that the EFI page tables are only available during EFI
runtime calls since that subject has come up a fair numbers of times
in the past.

Additionally, add the EFI region start and end addresses to the table
so that it's possible to see at a glance where they fall in relation
to other regions.

Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>,
Cc: Stephen Smalley <sds@xxxxxxxxxxxxx>
Signed-off-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Documentation/x86/x86_64/mm.txt | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
index 05712ac83e38..a9885bb1ac22 100644
--- a/Documentation/x86/x86_64/mm.txt
+++ b/Documentation/x86/x86_64/mm.txt
@@ -16,6 +16,8 @@ ffffec0000000000 - fffffc0000000000 (=44 bits) kasan shadow memory (16TB)
... unused hole ...
ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
... unused hole ...
+ffffffef00000000 - ffffffff00000000 (=64 GB) EFI region mapping space
+... unused hole ...
ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0
ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space
ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
@@ -32,11 +34,9 @@ reference.
Current X86-64 implementations only support 40 bits of address space,
but we support up to 46 bits. This expands into MBZ space in the page tables.

-We map EFI runtime services in the aforementioned PGD in the virtual
-range of 64Gb (arbitrarily set, can be raised if needed)
-0xffffffef00000000 - 0xffffffff00000000
+We map EFI runtime services in the efi_pgd PGD in the virtual range of
+64Gb (arbitrarily set, can be raised if needed). The mappings are not
+part of any other kernel PGD and are only available during EFI runtime

-Andi Kleen, Jul 2004

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