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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 07960C3A5A2 for ; Sat, 21 Sep 2019 01:47:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A73692086A for ; Sat, 21 Sep 2019 01:47:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="tkkE5RjY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A73692086A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3B2486B0003; Fri, 20 Sep 2019 21:47:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3636C6B0006; Fri, 20 Sep 2019 21:47:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 279556B000A; Fri, 20 Sep 2019 21:47:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0073.hostedemail.com [216.40.44.73]) by kanga.kvack.org (Postfix) with ESMTP id 072ED6B0003 for ; Fri, 20 Sep 2019 21:47:54 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 9B27B52C0 for ; Sat, 21 Sep 2019 01:47:54 +0000 (UTC) X-FDA: 75957241668.02.wood54_45076c3cf3e11 X-HE-Tag: wood54_45076c3cf3e11 X-Filterd-Recvd-Size: 5513 Received: from mail-qk1-f196.google.com (mail-qk1-f196.google.com [209.85.222.196]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Sat, 21 Sep 2019 01:47:54 +0000 (UTC) Received: by mail-qk1-f196.google.com with SMTP id u184so9270570qkd.4 for ; Fri, 20 Sep 2019 18:47:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SfnM1kEHJB20PsJ9Y6PlF1EQF63o4NAR1hJNSU7CBGI=; b=tkkE5RjYXLE5liJly0UZ1C2zR1unTObtqkwLG9O2vtHUo/FxtTrXn/I/XedWNWr3O+ SYH65W5DXjgHt0rw9dbx0r5XQubscRGBGWQTrS5f0NJMv5cJiXzD7KcbmylftW4bmr0x CNnXmPQIUftqYie7SHHeOC8VjlJvNVI5BSUcLqYfRHCsnmuiBMh7MlbmCI7HNi908SdO vr8ricHxIS3N/1Vp1WnSIsNOkEHhXpic9JWWn4qG5Vq2H9QQMP3b0DJTXabldr05l4Z5 3OzXUubbzV/pWKlg59pjmH/s04beFA+DWFsnmr62b9Y66RCjRruLBWdY8o062Z9x44LY BHxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SfnM1kEHJB20PsJ9Y6PlF1EQF63o4NAR1hJNSU7CBGI=; b=AJeCyA6AiRxqvKiD9jQXMOH7FU1PAJof3/pCy/evvrFNPpTPxQ9ApsWEDuFiWn9XsD CqkCPjELeqzvkIA7aQiW43tdZOZkp7hhDBF7pq54kzZ5kvTkchcUL1Uo6UnWgEGXvhgy KTAr5j0LcHcasq+ymFxgBajN+KPOI+ZjhwPeW6Mh9w/2opmdEGOUz766cflniqQio12/ EpxRV2Wo4C1fWJ/JoQj3DJxypwkmlQ3vp04OhPItvxJvtycI2rRHCuPpj3rXoFp9llJ4 mB/w0hTO/4X3TXwoekU+imxI0ixcHXOYNgOdZhjYPk3TELlYK/QXM9uRdktNfoJFXlhf 1Nvw== X-Gm-Message-State: APjAAAU9ODJD93fsM9PrCAof50QoL1Z/lTfj3EcOA0qMPSHiz7H0zE+f Kj/nnTW5mZS6SbXuutA47JdK25QmQHjv9ANZLtA= X-Google-Smtp-Source: APXvYqxfrUkE2P8KhqREWnYt0e3UxiIb1UT3YF/aWByB8II0Vdjo+Cpoifzt08pkOeqd6kWySa/+M4j1cPEXI3fDK34= X-Received: by 2002:ae9:eb8c:: with SMTP id b134mr6500884qkg.377.1569030473789; Fri, 20 Sep 2019 18:47:53 -0700 (PDT) MIME-Version: 1.0 References: <1568994684-1425-1-git-send-email-hqjagain@gmail.com> <1a162778-41b9-4428-1058-82aaf82314b1@nvidia.com> In-Reply-To: From: Qiujun Huang Date: Sat, 21 Sep 2019 09:47:42 +0800 Message-ID: Subject: Re: [PATCH 3/3] mm:fix gup_pud_range To: John Hubbard Cc: akpm@linux-foundation.org, ira.weiny@intel.com, jgg@ziepe.ca, dan.j.williams@intel.com, rppt@linux.ibm.com, "Aneesh Kumar K.V" , keith.busch@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" 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 Sat, Sep 21, 2019 at 9:19 AM John Hubbard wrote: > > On 9/20/19 5:33 PM, Qiujun Huang wrote: > >> On 9/20/19 8:51 AM, Qiujun Huang wrote: > ... > >> It would be nice if this spelled out a little more clearly what's > >> wrong. I think you and Aneesh are saying that the entry is really > >> a swap entry, created by the MCE response to a bad page? > > do_machine_check-> > > do_memory_failure-> > > memory_failure-> > > hwpoison_user_mappings > > will updated PUD level PTE entry as a swap entry. > > > > static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > > unsigned long address, void *arg) > > { > > ... > > if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { > > pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); > > OK, that helps. Let's add something approximately like this to the > commit description: > > do_machine_check() > do_memory_failure() > memory_failure() > hw_poison_user_mappings() > try_to_unmap() > pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); > > ...and now we have a swap entry that indicates that the page entry > refers to a bad (and poisoned) page of memory, but gup_fast() at this > level of the page table was ignoring swap entries, and incorrectly > assuming that "!pxd_none() == valid and present". > > And this was not just a poisoned page problem, but a generaly swap entry > problem. So, any swap entry type (device memory migration, numa migration, > or just regular swapping) could lead to the same problem. > > Fix this by checking for pxd_present(), instead of pxd_none(). > > > > ... > >> > >>> > >>> Signed-off-by: Qiujun Huang > >>> --- > >>> mm/gup.c | 2 ++ > >>> 1 file changed, 2 insertions(+) > >>> > >>> diff --git a/mm/gup.c b/mm/gup.c > >>> index 98f13ab..6157ed9 100644 > >>> --- a/mm/gup.c > >>> +++ b/mm/gup.c > >>> @@ -2230,6 +2230,8 @@ static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end, > >>> next = pud_addr_end(addr, end); > >>> if (pud_none(pud)) > >>> return 0; > >>> + if (unlikely(!pud_present(pud))) > >>> + return 0; > >> > >> If the MCE hwpoison behavior puts in swap entries, then it seems like all > >> page table walkers would need to check for p*d_present(), and maybe at all > >> levels too, right? > > I think so > >> > > Should those changes be part of this fix, do you think? Yes, please.Thanks > > thanks, > -- > John Hubbard > NVIDIA