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The following commit:
d5052a7130a6 ("x86/efi: Unmap EFI boot services code/data regions from efi_pgd")
forgets to take two EFI modes into consideration, namely EFI_OLD_MEMMAP and
EFI_MIXED_MODE:
- EFI_OLD_MEMMAP is a legacy way of mapping EFI regions into swapper_pg_dir
using ioremap() and init_memory_mapping(). This feature can be enabled by
passing "efi=old_map" as kernel command line argument. But,
efi_unmap_pages() unmaps EFI boot services code/data regions *only* from
efi_pgd and hence cannot be used for unmapping EFI boot services code/data
regions from swapper_pg_dir.
Introduce a temporary fix to not unmap EFI boot services code/data regions
when EFI_OLD_MEMMAP is enabled while working on a real fix.
- EFI_MIXED_MODE is another feature where a 64-bit kernel runs on a
64-bit platform crippled by a 32-bit firmware. To support EFI_MIXED_MODE,
all RAM (i.e. namely EFI regions like EFI_CONVENTIONAL_MEMORY,
EFI_LOADER_<CODE/DATA>, EFI_BOOT_SERVICES_<CODE/DATA> and
EFI_RUNTIME_CODE/DATA regions) is mapped into efi_pgd all the time to
facilitate EFI runtime calls access it's arguments in 1:1 mode.
Hence, don't unmap EFI boot services code/data regions when booted in mixed mode.
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20181222022234.7573-1-sai.praneeth.prakhya@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.