Here' my first attempt to bring boot-time between 4- and 5-level paging. It looks not too terrible to me. I've expected it to be worse. The basic idea is to implement the same logic as pgtable-nop4d.h provides, but at runtime. Runtime folding is only implemented for CONFIG_X86_5LEVEL=y case. With the option disabled, we do compile-time folding. Initially, I tried to fold pgd instread. I've got to shell, but it required a lot of hacks as kernel threats pgd in a special way. Few things are broken (see patch 7/8) and many things are not yet tested. So more work is required. I also haven't evaluated performance impact. We can look into some form of boot-time code patching later if required. Please review. Any feedback is welcome. Kirill A. Shutemov (8): x86/boot/compressed/64: Detect and handle 5-level paging at boot-time x86/mm: Make virtual memory layout movable for CONFIG_X86_5LEVEL x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable x86/mm: Handle boot-time paging mode switching at early boot x86/mm: Fold p4d page table layer at runtime x86/mm: Replace compile-time checks for 5-level with runtime-time x86/mm: Hacks for boot-time switching between 4- and 5-level paging x86/mm: Allow to boot without la57 if CONFIG_X86_5LEVEL=y arch/x86/Kconfig | 4 +- arch/x86/boot/compressed/head_64.S | 37 ++++++++++++++++++ arch/x86/entry/entry_64.S | 5 +++ arch/x86/include/asm/kaslr.h | 4 -- arch/x86/include/asm/page_64.h | 4 ++ arch/x86/include/asm/page_64_types.h | 15 +++----- arch/x86/include/asm/paravirt.h | 3 +- arch/x86/include/asm/pgalloc.h | 5 ++- arch/x86/include/asm/pgtable.h | 10 ++++- arch/x86/include/asm/pgtable_32.h | 2 + arch/x86/include/asm/pgtable_64_types.h | 46 ++++++++++++++-------- arch/x86/include/asm/processor.h | 2 +- arch/x86/include/asm/required-features.h | 8 +--- arch/x86/kernel/head64.c | 66 ++++++++++++++++++++++++++++---- arch/x86/kernel/head_64.S | 22 +++++++---- arch/x86/mm/dump_pagetables.c | 11 ++---- arch/x86/mm/ident_map.c | 2 +- arch/x86/mm/init_64.c | 30 +++++++++------ arch/x86/mm/kaslr.c | 16 ++------ arch/x86/platform/efi/efi_64.c | 4 +- arch/x86/power/hibernate_64.c | 4 +- arch/x86/xen/Kconfig | 2 +- arch/x86/xen/mmu_pv.c | 2 +- 23 files changed, 208 insertions(+), 96 deletions(-) -- 2.11.0
