path: root/Documentation/x86
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authorBorislav Petkov <bp@suse.de>2013-10-31 16:25:08 (GMT)
committerMatt Fleming <matt.fleming@intel.com>2013-11-02 11:09:36 (GMT)
commitd2f7cbe7b26a74dbbbf8f325b2a6fd01bc34032c (patch)
tree69d2c1f92120fa532c77cf8634418b7622d55692 /Documentation/x86
parent82f0712ca0f947170e785300b5c39d9c25e2f6ff (diff)
x86/efi: Runtime services virtual mapping
We map the EFI regions needed for runtime services non-contiguously, with preserved alignment on virtual addresses starting from -4G down for a total max space of 64G. This way, we provide for stable runtime services addresses across kernels so that a kexec'd kernel can still use them. Thus, they're mapped in a separate pagetable so that we don't pollute the kernel namespace. Add an efi= kernel command line parameter for passing miscellaneous options and chicken bits from the command line. While at it, add a chicken bit called "efi=old_map" which can be used as a fallback to the old runtime services mapping method in case there's some b0rkage with a particular EFI implementation (haha, it is hard to hold up the sarcasm here...). Also, add the UEFI RT VA space to Documentation/x86/x86_64/mm.txt. Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Diffstat (limited to 'Documentation/x86')
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
index 881582f..c584a51 100644
--- a/Documentation/x86/x86_64/mm.txt
+++ b/Documentation/x86/x86_64/mm.txt
@@ -28,4 +28,11 @@ 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
-Andi Kleen, Jul 2004

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