x86-64: finish cleanup_highmaps()'s job wrt. _brk_end (49834396) · Commits · 戴 / test

With the introduction of the .brk section, special care must be taken that no unused page table entries remain if _brk_end and _end are separated by a 2M page boundary. cleanup_highmap() runs very early and hence cannot take care of that, hence potential entries needing to be removed past _brk_end must be cleared once the brk allocator has done its job. [ Impact: avoids undesirable TLB aliases ] Signed-off-by:

Jan Beulich <jbeulich@novell.com> Signed-off-by:

H. Peter Anvin <hpa@zytor.com>

arch/x86/mm/init.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -7,6 +7,7 @@
		#include <asm/page.h>
		#include <asm/page_types.h>
		#include <asm/sections.h>
		#include <asm/setup.h>
		#include <asm/system.h>
		#include <asm/tlbflush.h>

		@@ -304,8 +305,23 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
		#endif

		#ifdef CONFIG_X86_64
		if (!after_bootmem)
		if (!after_bootmem && !start) {
		pud_t *pud;
		pmd_t *pmd;

		mmu_cr4_features = read_cr4();

		/*
		* _brk_end cannot change anymore, but it and _end may be
		* located on different 2M pages. cleanup_highmap(), however,
		* can only consider _end when it runs, so destroy any
		* mappings beyond _brk_end here.
		*/
		pud = pud_offset(pgd_offset_k(_brk_end), _brk_end);
		pmd = pmd_offset(pud, _brk_end - 1);
		while (++pmd <= pmd_offset(pud, (unsigned long)_end - 1))
		pmd_clear(pmd);
		}
		#endif
		__flush_tlb_all();

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