• Kirill A. Shutemov's avatar
    x86/boot/compressed: Enable 5-level paging during decompression stage · 34bbb000
    Kirill A. Shutemov authored
    We need to cover two basic cases: when bootloader left us in 32-bit mode
    and when bootloader enabled long mode.
    
    The patch implements unified codepath to enabled 5-level paging for both
    cases. It means case when we start in 32-bit mode, we first enable long
    mode with 4-level and then switch over to 5-level paging.
    
    Switching from 4-level to 5-level paging is not trivial. We cannot do it
    directly. Setting LA57 in long mode would trigger #GP. So we need to
    switch off long mode first and the then re-enable with 5-level paging.
    
    NOTE: The need of switching off long mode means we are in trouble if
    bootloader put us above 4G boundary. If bootloader wants to boot 5-level
    paging kernel, it has to put kernel below 4G or enable 5-level paging on
    it's own, so we could avoid the step.
    Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-arch@vger.kernel.org
    Cc: linux-mm@kvack.org
    Link: http://lkml.kernel.org/r/20170606113133.22974-7-kirill.shutemov@linux.intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    34bbb000
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