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=-8.2 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=unavailable 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 B3B86C76193 for ; Mon, 29 Jul 2019 12:30:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6B129214AE for ; Mon, 29 Jul 2019 12:30:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B129214AE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CCF688E0003; Mon, 29 Jul 2019 08:30:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C57D08E0002; Mon, 29 Jul 2019 08:30:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AF87E8E0003; Mon, 29 Jul 2019 08:30:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 5EAF98E0002 for ; Mon, 29 Jul 2019 08:30:10 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id l26so38187233eda.2 for ; Mon, 29 Jul 2019 05:30:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:subject:to:cc :references:from:message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=VhZ0weODvxVPuYMMMd5+/UN55Ksi6jDNOcYU1PMKVws=; b=BVb7tnTdY7NXpniQeCq2AYgeY5Y8/wXF7KYld4HjWSXuUAJcnIs9DAKKL1lvTBJWLH NnRAzqvfBgnwowsL88lEwAYK4shDzYW0/ZIMJw2Xy608f9M3Qcsdx3PS3O2f1Y+2/yM6 Wl9hlZ4ZDxbuJZ6dl3HF77gYY5NZKiHhBvFQv6oH+9DTHwOkCcapE25te5584lGPK0+t ZwMBv95hwQoUvuSVFvQsAUngLpOmNfGo2qvi5e7vNeZCIAcL/9UJ5BkOa2BtIYHp002c itL09i560rGPLwavhRNOLnPMOFBW70MTnjVwma54iq6OqGD3smFEA9Ga4hKl3Ao2C8QQ bgyw== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=steven.price@arm.com X-Gm-Message-State: APjAAAUMfysRrvaxIIEzYovZnXQqAjz8vIav4kselyBwO4xZa5bfBh5S k9qQoVDzvsAk++GYWlb3cMCjfx88FJFjuvlpgnkLyOo3nXIazomkJbyf+osztl0ucQnFD6FJQQx wLp0aYsbjosJrpKKsKz/eRQeST17vJ2IcSgrH1LW9h3nEKStyBeM+dDFMmM5dGyaXhA== X-Received: by 2002:a17:906:fac7:: with SMTP id lu7mr50258797ejb.109.1564403409925; Mon, 29 Jul 2019 05:30:09 -0700 (PDT) X-Google-Smtp-Source: APXvYqx4IwKit+3ulZLvXo9U6rEI1F5luUvPc73GUw8s9wbZyBEEEDfSpI2IJ5RZRrd6btkRMiwG X-Received: by 2002:a17:906:fac7:: with SMTP id lu7mr50258735ejb.109.1564403409058; Mon, 29 Jul 2019 05:30:09 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1564403409; cv=none; d=google.com; s=arc-20160816; b=BiMoOCnySZ9tjEVr+ch+YZl5gCp3hc1iWYmQx1LL0zITsdNczopcLoZ8VlR/m3C0my iT0SG9uoXnJ7tMEicWMQ4BFcqFvM3Rec4982h2U0XjrWoLRcP97Soh0tuMdrxL22JACb 6424o0Gj4prJ6o2xziSLsqpxJjY3BYH+3sNtJJHmnf/JmQBGj3G2fBys0NOm0h9rnLwk dFfUJmrmJowKGjlS2at0YRYej7CehT81pFQyktGi+hf3tt6Acick2ju2n9j7QgJemyX5 uKuqCv0RZDEV83msSoPJdHg/xhQr/E0d0lz3dbi3KaBEuhu8XLJWwzS2fevkMRdjKUT5 wyVQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject; bh=VhZ0weODvxVPuYMMMd5+/UN55Ksi6jDNOcYU1PMKVws=; b=ZOMsMa3J/M+zeVxDjJkqEf+Hf9/LzDXRj1Z0uGE/sEhxAXXa3Dy825Ht9259WKgX2e DO/jan1DreKaHOrfKWCd0VMxvrL3vnwksj3oYa1vRSoCd9sAkDMd6yi4Z0tHxab83ypl gEBtEv3av5rTl9AAuWcdzuYuwMHvapOHzaWtqGYXBgA4q9XpYHlw0SlK3Odfm/5q9W+V xhHNvgpeY3pt7t/HGPsm0/MGDCS48rMvg9tg1Z0c0dOWxU+vXvbiQc88bH4OBoiBKrB4 XM96wn3HKDD8IETxps/IKVGasTIhplmCGKRQldfZVkX4uoQBGoEjoo/Wv1f0TQNHh1oI E0Qg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=steven.price@arm.com Received: from foss.arm.com (foss.arm.com. [217.140.110.172]) by mx.google.com with ESMTP id ec8si14475126ejb.184.2019.07.29.05.30.07 for ; Mon, 29 Jul 2019 05:30:08 -0700 (PDT) Received-SPF: pass (google.com: domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=steven.price@arm.com 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 1D1DA28; Mon, 29 Jul 2019 05:30:07 -0700 (PDT) Received: from [10.1.196.133] (e112269-lin.cambridge.arm.com [10.1.196.133]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 75AB43F575; Mon, 29 Jul 2019 05:29:59 -0700 (PDT) Subject: Re: [PATCH v9 12/21] mm: pagewalk: Allow walking without vma To: Anshuman Khandual , linux-mm@kvack.org Cc: Mark Rutland , x86@kernel.org, Arnd Bergmann , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Dave Hansen , linux-kernel@vger.kernel.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, "Liang, Kan" References: <20190722154210.42799-1-steven.price@arm.com> <20190722154210.42799-13-steven.price@arm.com> <7fc50563-7d5d-7270-5a6a-63769e9c335a@arm.com> From: Steven Price Message-ID: <5aff70f7-67a5-c7e8-5fec-8182dea0da0c@arm.com> Date: Mon, 29 Jul 2019 13:29:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <7fc50563-7d5d-7270-5a6a-63769e9c335a@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 28/07/2019 15:20, Anshuman Khandual wrote: > > > On 07/22/2019 09:12 PM, Steven Price wrote: >> Since 48684a65b4e3: "mm: pagewalk: fix misbehavior of walk_page_range >> for vma(VM_PFNMAP)", page_table_walk() will report any kernel area as >> a hole, because it lacks a vma. >> >> This means each arch has re-implemented page table walking when needed, >> for example in the per-arch ptdump walker. >> >> Remove the requirement to have a vma except when trying to split huge >> pages. >> >> Signed-off-by: Steven Price >> --- >> mm/pagewalk.c | 25 +++++++++++++++++-------- >> 1 file changed, 17 insertions(+), 8 deletions(-) >> >> diff --git a/mm/pagewalk.c b/mm/pagewalk.c >> index 98373a9f88b8..1cbef99e9258 100644 >> --- a/mm/pagewalk.c >> +++ b/mm/pagewalk.c >> @@ -36,7 +36,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, >> do { >> again: >> next = pmd_addr_end(addr, end); >> - if (pmd_none(*pmd) || !walk->vma) { >> + if (pmd_none(*pmd)) { >> if (walk->pte_hole) >> err = walk->pte_hole(addr, next, walk); >> if (err) >> @@ -59,9 +59,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, >> if (!walk->pte_entry) >> continue; >> >> - split_huge_pmd(walk->vma, pmd, addr); >> - if (pmd_trans_unstable(pmd)) >> - goto again; >> + if (walk->vma) { >> + split_huge_pmd(walk->vma, pmd, addr); > > Check for a PMD THP entry before attempting to split it ? split_huge_pmd does the check for us: > #define split_huge_pmd(__vma, __pmd, __address) \ > do { \ > pmd_t *____pmd = (__pmd); \ > if (is_swap_pmd(*____pmd) || pmd_trans_huge(*____pmd) \ > || pmd_devmap(*____pmd)) \ > __split_huge_pmd(__vma, __pmd, __address, \ > false, NULL); \ > } while (0) And this isn't a change from the previous code - only that the entry is no longer split when walk->vma==NULL. >> + if (pmd_trans_unstable(pmd)) >> + goto again; >> + } else if (pmd_leaf(*pmd)) { >> + continue; >> + } >> + >> err = walk_pte_range(pmd, addr, next, walk); >> if (err) >> break; >> @@ -81,7 +86,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, >> do { >> again: >> next = pud_addr_end(addr, end); >> - if (pud_none(*pud) || !walk->vma) { >> + if (pud_none(*pud)) { >> if (walk->pte_hole) >> err = walk->pte_hole(addr, next, walk); >> if (err) >> @@ -95,9 +100,13 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, >> break; >> } >> >> - split_huge_pud(walk->vma, pud, addr); >> - if (pud_none(*pud)) >> - goto again; >> + if (walk->vma) { >> + split_huge_pud(walk->vma, pud, addr); > > Check for a PUD THP entry before attempting to split it ? Same as above. >> + if (pud_none(*pud)) >> + goto again; >> + } else if (pud_leaf(*pud)) { >> + continue; >> + } > > This is bit cryptic. walk->vma check should be inside a helper is_user_page_table() > or similar to make things clear. p4d_leaf() check missing in walk_p4d_range() for > kernel page table walk ? Wondering if p?d_leaf() test should be moved earlier while > calling p?d_entry() for kernel page table walk. I wasn't sure if it was worth putting p4d_leaf() and pgd_leaf() checks in (yet). No architecture that I know of uses such large pages. I'm not sure what you mean by moving the p?d_leaf() test earlier? Can you explain with an example? Thanks, Steve