From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44538C49ED7 for ; Fri, 13 Sep 2019 08:42:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22F7E20CC7 for ; Fri, 13 Sep 2019 08:42:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387561AbfIMImq (ORCPT ); Fri, 13 Sep 2019 04:42:46 -0400 Received: from foss.arm.com ([217.140.110.172]:40170 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387499AbfIMImq (ORCPT ); Fri, 13 Sep 2019 04:42:46 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D181628; Fri, 13 Sep 2019 01:42:44 -0700 (PDT) Received: from [10.162.41.125] (p8cg001049571a15.blr.arm.com [10.162.41.125]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A21F43F59C; Fri, 13 Sep 2019 01:42:34 -0700 (PDT) Subject: Re: [PATCH] mm/pgtable/debug: Fix test validating architecture page table helpers To: Christophe Leroy , linux-mm@kvack.org Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Heiko Carstens , Michal Hocko , Dave Hansen , Paul Mackerras , sparclinux@vger.kernel.org, Dan Williams , linux-s390@vger.kernel.org, Jason Gunthorpe , x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Tetsuo Handa , Vlastimil Babka , linux-snps-arc@lists.infradead.org, Kees Cook , Mark Brown , "Kirill A . Shutemov" , Thomas Gleixner , Gerald Schaefer , linux-arm-kernel@lists.infradead.org, Sri Krishna chowdary , Masahiro Yamada , Greg Kroah-Hartman , Ard Biesheuvel , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Paul Burton , Mike Rapoport , Vineet Gupta , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" References: <1892b37d1fd9a4ed39e76c4b999b6556077201c0.1568355752.git.christophe.leroy@c-s.fr> <527dd29d-45fa-4d83-1899-6cbf268dd749@arm.com> From: Anshuman Khandual Message-ID: Date: Fri, 13 Sep 2019 14:12:45 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On 09/13/2019 12:41 PM, Christophe Leroy wrote: > > > Le 13/09/2019 à 09:03, Christophe Leroy a écrit : >> >> >> Le 13/09/2019 à 08:58, Anshuman Khandual a écrit : >>> On 09/13/2019 11:53 AM, Christophe Leroy wrote: >>>> Fix build failure on powerpc. >>>> >>>> Fix preemption imbalance. >>>> >>>> Signed-off-by: Christophe Leroy >>>> --- >>>>   mm/arch_pgtable_test.c | 3 +++ >>>>   1 file changed, 3 insertions(+) >>>> >>>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c >>>> index 8b4a92756ad8..f2b3c9ec35fa 100644 >>>> --- a/mm/arch_pgtable_test.c >>>> +++ b/mm/arch_pgtable_test.c >>>> @@ -24,6 +24,7 @@ >>>>   #include >>>>   #include >>>>   #include >>>> +#include >>> >>> This is okay. >>> >>>>   #include >>>>   #include >>>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void) >>>>       p4d_clear_tests(p4dp); >>>>       pgd_clear_tests(mm, pgdp); >>>> +    pte_unmap(ptep); >>>> + >>> >>> Now the preemption imbalance via pte_alloc_map() path i.e >>> >>> pte_alloc_map() -> pte_offset_map() -> kmap_atomic() >>> >>> Is not this very much powerpc 32 specific or this will be applicable >>> for all platform which uses kmap_XXX() to map high memory ? >>> >> >> See https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91 >> >> I think it applies at least to all arches using the generic implementation. >> >> Applies also to arm: >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52 >> >> Applies also to mips: >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47 >> >> Same on sparc: >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52 >> >> Same on x86: >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34 >> >> I have not checked others, but I guess it is like that for all. >> > > > Seems like I answered too quickly. All kmap_atomic() do preempt_disable(), but not all pte_alloc_map() call kmap_atomic(). > > However, for instance ARM does: > > https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/include/asm/pgtable.h#L200 > > And X86 as well: > > https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/include/asm/pgtable_32.h#L51 > > Microblaze also: > > https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/microblaze/include/asm/pgtable.h#L495 All the above platforms checks out to be using k[un]map_atomic(). I am wondering whether any of the intermediate levels will have similar problems on any these 32 bit platforms or any other platforms which might be using generic k[un]map_atomic(). There can be many permutations here. p4dp = p4d_alloc(mm, pgdp, vaddr); pudp = pud_alloc(mm, p4dp, vaddr); pmdp = pmd_alloc(mm, pudp, vaddr); Otherwise pte_alloc_map()/pte_unmap() looks good enough which will atleast take care of a known failure.