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=-13.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,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 5FBD6C4CEC7 for ; Mon, 16 Sep 2019 09:16:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AF37214AF for ; Mon, 16 Sep 2019 09:16:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="yNH4GN7L" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731805AbfIPJQ3 (ORCPT ); Mon, 16 Sep 2019 05:16:29 -0400 Received: from mail-ed1-f67.google.com ([209.85.208.67]:40281 "EHLO mail-ed1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731764AbfIPJQ2 (ORCPT ); Mon, 16 Sep 2019 05:16:28 -0400 Received: by mail-ed1-f67.google.com with SMTP id v38so32412060edm.7 for ; Mon, 16 Sep 2019 02:16:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=vBZCS9nU1fSH+kmSCYigm2Yq8YU/srN9xKPMLdxx9uA=; b=yNH4GN7LaJOP3yS9aV4fF11ma1PFEb7h83O4Jf9wGnCAwQ3sIB0HjqygkTPkLbIX4i fpzZFr9Ng8cKCy3x990mhweiHyLCASKWNlnkwpho9OSGlLFttD271s7WNCgaDENT5il7 6LScrSQDK35mJXcuHW16ivhg6hD9hRDBcPp0a4CIxMBbCnau5Ijn3LRBS7HJ5NxH96Xm T9cm3x8hG9/hCBdsRQ4+RiD1j1PDzIzWfU5wGcU0clDw5lAiWT+qS+6kBai15OK2tuXI j3Vc+mNUlZL8X1pfK/Pp4igTpzakDaZNk//o1k0AcgB8w0tKGOglAuPzSFVBsTeTCHRF CQaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=vBZCS9nU1fSH+kmSCYigm2Yq8YU/srN9xKPMLdxx9uA=; b=L2ClC2I+rCZK7jDuWAsk+T/hGQsCx5oIupw18G7uRMXSTMKUCtC8v1xipnrRS9gjO2 ney9+Gy7TCXsgkNkXYm+d0Em3RivAe3OxYmjzWs6R4J8JDArFfe5gxlxNiIXB5T10UAG NqQksQmCCKwfW04Uj7H8OxQpyzxCDr6a+12ygCA38uBGusXUtXPT7dtfOv8p74h+wk+x 8XjqBEMzXDCbMh8+1WIADtojEsJOI+T8VI2lVHwxp8dc5S5cutWurP5eSeyDf6P6Xzka /enby9n1qzutehYhID8HeRK6SnQuqrIAHaI/dpGHQ0pZma/VVjqi2oEE7fMZVX9PNaKV 1FQQ== X-Gm-Message-State: APjAAAVv+grURKirFuCX2QgjSyTPSQrnCQnyx86bo3CKc3MUVQHDOFEh fiNNSw8cD7O1l6vXtIMEWstnIA== X-Google-Smtp-Source: APXvYqyGScQN03qDrXuVbBMNDdbJlq+zqcHgLnsomhbDkQ6dQ4qNnJhT5ZwIkawoSd3+haiCNIOt4w== X-Received: by 2002:a50:87ca:: with SMTP id 10mr9263258edz.77.1568625387310; Mon, 16 Sep 2019 02:16:27 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id br15sm3577556ejb.2.2019.09.16.02.16.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Sep 2019 02:16:26 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id 85A0A104174; Mon, 16 Sep 2019 12:16:28 +0300 (+03) Date: Mon, 16 Sep 2019 12:16:28 +0300 From: "Kirill A. Shutemov" To: Jia He Cc: Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Punit Agrawal , Anshuman Khandual , Jun Yao , Alex Van Brunt , Robin Murphy , Thomas Gleixner , Andrew Morton , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Ralph Campbell , hejianet@gmail.com Subject: Re: [PATCH v3 2/2] mm: fix double page fault on arm64 if PTE_AF is cleared Message-ID: <20190916091628.bkuvd3g3ie3x6qav@box.shutemov.name> References: <20190913163239.125108-1-justin.he@arm.com> <20190913163239.125108-3-justin.he@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190913163239.125108-3-justin.he@arm.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 14, 2019 at 12:32:39AM +0800, Jia He wrote: > When we tested pmdk unit test [1] vmmalloc_fork TEST1 in arm64 guest, there > will be a double page fault in __copy_from_user_inatomic of cow_user_page. > > Below call trace is from arm64 do_page_fault for debugging purpose > [ 110.016195] Call trace: > [ 110.016826] do_page_fault+0x5a4/0x690 > [ 110.017812] do_mem_abort+0x50/0xb0 > [ 110.018726] el1_da+0x20/0xc4 > [ 110.019492] __arch_copy_from_user+0x180/0x280 > [ 110.020646] do_wp_page+0xb0/0x860 > [ 110.021517] __handle_mm_fault+0x994/0x1338 > [ 110.022606] handle_mm_fault+0xe8/0x180 > [ 110.023584] do_page_fault+0x240/0x690 > [ 110.024535] do_mem_abort+0x50/0xb0 > [ 110.025423] el0_da+0x20/0x24 > > The pte info before __copy_from_user_inatomic is (PTE_AF is cleared): > [ffff9b007000] pgd=000000023d4f8003, pud=000000023da9b003, pmd=000000023d4b3003, pte=360000298607bd3 > > As told by Catalin: "On arm64 without hardware Access Flag, copying from > user will fail because the pte is old and cannot be marked young. So we > always end up with zeroed page after fork() + CoW for pfn mappings. we > don't always have a hardware-managed access flag on arm64." > > This patch fix it by calling pte_mkyoung. Also, the parameter is > changed because vmf should be passed to cow_user_page() > > [1] https://github.com/pmem/pmdk/tree/master/src/test/vmmalloc_fork > > Reported-by: Yibo Cai > Signed-off-by: Jia He > --- > mm/memory.c | 30 +++++++++++++++++++++++++----- > 1 file changed, 25 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index e2bb51b6242e..a64af6495f71 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -118,6 +118,13 @@ int randomize_va_space __read_mostly = > 2; > #endif > > +#ifndef arch_faults_on_old_pte > +static inline bool arch_faults_on_old_pte(void) > +{ > + return false; > +} > +#endif > + > static int __init disable_randmaps(char *s) > { > randomize_va_space = 0; > @@ -2140,7 +2147,8 @@ static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, > return same; > } > > -static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma) > +static inline void cow_user_page(struct page *dst, struct page *src, > + struct vm_fault *vmf) > { > debug_dma_assert_idle(src); > > @@ -2152,20 +2160,32 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo > */ > if (unlikely(!src)) { > void *kaddr = kmap_atomic(dst); > - void __user *uaddr = (void __user *)(va & PAGE_MASK); > + void __user *uaddr = (void __user *)(vmf->address & PAGE_MASK); > + pte_t entry; > > /* > * This really shouldn't fail, because the page is there > * in the page tables. But it might just be unreadable, > * in which case we just give up and fill the result with > - * zeroes. > + * zeroes. If PTE_AF is cleared on arm64, it might > + * cause double page fault. So makes pte young here > */ > + if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) { > + spin_lock(vmf->ptl); > + entry = pte_mkyoung(vmf->orig_pte); Should't you re-validate that orig_pte after re-taking ptl? It can be stale by now. > + if (ptep_set_access_flags(vmf->vma, vmf->address, > + vmf->pte, entry, 0)) > + update_mmu_cache(vmf->vma, vmf->address, > + vmf->pte); > + spin_unlock(vmf->ptl); > + } > + > if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) > clear_page(kaddr); > kunmap_atomic(kaddr); > flush_dcache_page(dst); > } else > - copy_user_highpage(dst, src, va, vma); > + copy_user_highpage(dst, src, vmf->address, vmf->vma); > } > > static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma) > @@ -2318,7 +2338,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) > vmf->address); > if (!new_page) > goto oom; > - cow_user_page(new_page, old_page, vmf->address, vma); > + cow_user_page(new_page, old_page, vmf); > } > > if (mem_cgroup_try_charge_delay(new_page, mm, GFP_KERNEL, &memcg, false)) > -- > 2.17.1 > > -- Kirill A. Shutemov