From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f181.google.com (mail-wi0-f181.google.com [209.85.212.181]) by kanga.kvack.org (Postfix) with ESMTP id 905B0280003 for ; Sat, 13 Jun 2015 05:49:55 -0400 (EDT) Received: by wigg3 with SMTP id g3so34744517wig.1 for ; Sat, 13 Jun 2015 02:49:55 -0700 (PDT) Received: from mail-wi0-x231.google.com (mail-wi0-x231.google.com. [2a00:1450:400c:c05::231]) by mx.google.com with ESMTPS id en9si7882911wib.46.2015.06.13.02.49.52 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 13 Jun 2015 02:49:53 -0700 (PDT) Received: by wifx6 with SMTP id x6so34980907wif.0 for ; Sat, 13 Jun 2015 02:49:52 -0700 (PDT) From: Ingo Molnar Subject: [PATCH 12/12] x86/mm: Simplify pgd_alloc() Date: Sat, 13 Jun 2015 11:49:15 +0200 Message-Id: <1434188955-31397-13-git-send-email-mingo@kernel.org> In-Reply-To: <1434188955-31397-1-git-send-email-mingo@kernel.org> References: <1434188955-31397-1-git-send-email-mingo@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Waiman Long 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 Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Waiman Long Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar --- 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 7cca42c01677..d7d341e57e33 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org