x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable
For boot-time switching between 4- and 5-level paging we need to be able to fold p4d page table level at runtime. It requires variable PGDIR_SHIFT and PTRS_PER_P4D. The change doesn't affect the kernel image size much: text data bss dec hex filename 8628091 4734304 1368064 14730459 e0c4db vmlinux.before 8628393 4734340 1368064 14730797 e0c62d vmlinux.after Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180214111656.88514-7-kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Ingo Molnar

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@@ -19,7 +19,7 @@
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extern struct range pfn_mapped[E820_MAX_ENTRIES];
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static p4d_t tmp_p4d_table[PTRS_PER_P4D] __initdata __aligned(PAGE_SIZE);
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static p4d_t tmp_p4d_table[MAX_PTRS_PER_P4D] __initdata __aligned(PAGE_SIZE);
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static __init void *early_alloc(size_t size, int nid, bool panic)
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{
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