From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755202AbdEDPzW (ORCPT ); Thu, 4 May 2017 11:55:22 -0400 Received: from foss.arm.com ([217.140.101.70]:42530 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751214AbdEDPzF (ORCPT ); Thu, 4 May 2017 11:55:05 -0400 From: Punit Agrawal To: Catalin Marinas Cc: will.deacon@arm.com, David Woods , steve.capper@arm.com, tbaicar@codeaurora.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries References: <20170412140459.21824-1-punit.agrawal@arm.com> <20170412140459.21824-2-punit.agrawal@arm.com> <20170503124906.GA5622@e104818-lin.cambridge.arm.com> Date: Thu, 04 May 2017 16:55:03 +0100 In-Reply-To: <20170503124906.GA5622@e104818-lin.cambridge.arm.com> (Catalin Marinas's message of "Wed, 3 May 2017 13:49:06 +0100") Message-ID: <87lgqcy5uw.fsf@e105922-lin.cambridge.arm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Catalin Marinas writes: > On Wed, Apr 12, 2017 at 03:04:57PM +0100, Punit Agrawal wrote: >> When memory failure is enabled, a poisoned hugepage pte is marked as a >> swap entry. huge_pte_offset() does not return the poisoned page table >> entries when it encounters PUD/PMD hugepages. >> >> This behaviour of huge_pte_offset() leads to error such as below when >> munmap is called on poisoned hugepages. >> >> [ 344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074. >> >> Fix huge_pte_offset() to return the poisoned pte which is then >> appropriately handled by the generic layer code. >> >> Signed-off-by: Punit Agrawal >> Cc: Catalin Marinas >> Cc: Steve Capper >> Cc: David Woods >> --- >> arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++----- >> 1 file changed, 15 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c >> index 7514a000e361..5f1832165d69 100644 >> --- a/arch/arm64/mm/hugetlbpage.c >> +++ b/arch/arm64/mm/hugetlbpage.c >> @@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr) >> pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd); >> if (!pgd_present(*pgd)) >> return NULL; >> - pud = pud_offset(pgd, addr); >> - if (!pud_present(*pud)) >> - return NULL; >> >> - if (pud_huge(*pud)) >> + pud = pud_offset(pgd, addr); >> + /* >> + * In case of HW Poisoning, a hugepage pud/pmd can contain >> + * poisoned entries. Poisoned entries are marked as swap >> + * entries. >> + * >> + * For puds/pmds that are not present, check to see if it >> + * could be a swap entry (!present and !none). >> + */ >> + if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud)) >> return (pte_t *)pud; > > Since we use puds as huge pages, can we just change pud_present() to > match the pmd_present()? I'd like to see similar checks for pud and pmd, > it would be easier to follow. Something like (unchecked): > > if (pud_none(*pud)) > return NULL; > /* swap or huge page */ > if (!pud_present(*pud) || pud_huge(*pud)) > return (pte_t *)pud; > /* table; check the next level */ > >> + >> pmd = pmd_offset(pud, addr); >> - if (!pmd_present(*pmd)) >> + if (pmd_none(*pmd)) >> return NULL; >> + if (!pmd_present(*pmd) && !pmd_none(*pmd)) >> + return (pte_t *)pmd; > > At this point, we already know that pmd_none(*pmd) is false, no ned to > check it again. Indeed - I was avoiding changing the function to drop contiguous hugepage support which follows this hunk. I've made changes locally based on your suggestion and will post a revised version after the merge window. Thanks, Punit