Messages in this thread Patch in this message | | | From | Ingo Molnar <> | Subject | [PATCH 12/12] x86/mm: Simplify pgd_alloc() | Date | Thu, 11 Jun 2015 16:07:17 +0200 |
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Right now pgd_alloc() uses pgd_ctor(), which copies over the current swapper_pg_dir[] to a new task's PGD.
This is not necessary, it's enough if we clear it: the PGD will then be properly updated by arch_pgd_init_late().
Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Waiman Long <Waiman.Long@hp.com> Cc: linux-mm@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/mm/pgtable.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 0666f7796806..b1bd35f452ef 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -87,20 +87,6 @@ void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud) #define UNSHARED_PTRS_PER_PGD \ (SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD) -static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd) -{ - /* If the pgd points to a shared pagetable level (either the - ptes in non-PAE, or shared PMD in PAE), then just copy the - references from swapper_pg_dir. */ - if (CONFIG_PGTABLE_LEVELS == 2 || - (CONFIG_PGTABLE_LEVELS == 3 && SHARED_KERNEL_PMD) || - CONFIG_PGTABLE_LEVELS == 4) { - clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY, - swapper_pg_dir + KERNEL_PGD_BOUNDARY, - KERNEL_PGD_PTRS); - } -} - /* * List of all pgd's needed for non-PAE so it can invalidate entries * in both cached and uncached pgd's; not needed for PAE since the @@ -328,11 +314,16 @@ pgd_t *pgd_alloc(struct mm_struct *mm) goto out_free_pmds; /* - * No locking is needed here, as the PGD is still private, - * so no code walking the task list and looking at mm->pgd - * will be able to see it before it's fully constructed: + * Zero out the kernel portion here, we'll set them up in + * arch_pgd_init_late(), when the pgd is globally + * visible already per the task list, so that it cannot + * miss updates. + * + * We need to zero it here, to make sure arch_pgd_init_late() + * can initialize them without locking. */ - pgd_ctor(mm, pgd); + memset(pgd + KERNEL_PGD_BOUNDARY, 0, KERNEL_PGD_PTRS*sizeof(pgd_t)); + pgd_prepopulate_pmd(mm, pgd, pmds); return pgd; -- 2.1.4
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