Comment 7 for bug 1301590

Ok, I've cloned the ubuntu-trusty repo, used git bisect and found the culprit:

dc9c3ed611922e769b1fd595f8f99a93d69c026d is the first bad commit
commit dc9c3ed611922e769b1fd595f8f99a93d69c026d
Author: Borislav Petkov <email address hidden>
Date: Thu Oct 31 17:25:08 2013 +0100

    x86/efi: Runtime services virtual mapping

    BugLink: http://bugs.launchpad.net/bugs/1297658

    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 <email address hidden>
    Signed-off-by: Matt Fleming <email address hidden>
    (cherry picked from commit d2f7cbe7b26a74dbbbf8f325b2a6fd01bc34032c)
    Signed-off-by: Tim Gardner <email address hidden>

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:040000 040000 21376a74b6a2dc5dbe5b581677830b90bec72e49 95678fbb2d7178afb7866daf706dd7706d8da7e6 M arch
:040000 040000 bf1515bb7d32745424abf75d8ce58340f482e88c 59013df8e2ea1c112d96b982105b469917864c8f M include