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=-12.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT, USER_IN_DEF_DKIM_WL 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 1B3A8C43381 for ; Mon, 18 Feb 2019 20:48:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DFDEB2146E for ; Mon, 18 Feb 2019 20:48:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="NUQUzfw8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729707AbfBRUsu (ORCPT ); Mon, 18 Feb 2019 15:48:50 -0500 Received: from mail-it1-f195.google.com ([209.85.166.195]:34611 "EHLO mail-it1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727513AbfBRUsr (ORCPT ); Mon, 18 Feb 2019 15:48:47 -0500 Received: by mail-it1-f195.google.com with SMTP id d125so857481ith.1 for ; Mon, 18 Feb 2019 12:48:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=/NLpiy+j/zrpP+sVhQdIcgCVfL0HwEex4aRdsJ4vY8Q=; b=NUQUzfw8/x7dr0Q70sqUQawAGRy1k43ldVFkm4ZbYxr1A3YdpzcGBs+YvYXIOhmZr+ 45UfT9cky6fpnR0KZOUXAxs90kZDwfEffomg1cwN/PpVg0WEPS6aW5GpHLtuct5JMUJq K213WVXJIDZ0l/iI9bu25oOyzAcMIFxP79Nzr9hkj/tZezv0NOLTYFZ9AnOC59poJK9q 21/h5HJxE20vXVmiNlzp3I8scZNb5ELd+yb3+OnbaSox94ydiQ/+kUattnzPon/0+iDL dldi9AiGX42H8k9DyNw8FdUIZITG8BoFgW4sWn7w7K/aJ6rwcJ5lSHZ1Wj1Iso7Z53Ba dSvA== 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=/NLpiy+j/zrpP+sVhQdIcgCVfL0HwEex4aRdsJ4vY8Q=; b=kzbTIWpbZvGrcEnFUzpg9K9d4mBggSCtHZMmgQWGMyS7ru0v0VMiXJUY+LEOYuPFIJ LuWyPRcExmaS0wMgItCsvY7PZw7Qt9zUQVdjTCBiprYYP+l1BOrGmHO8dPuJzCOIwitB s9cYnz/YH59Cr71fuHdAQM64yEW445Whv54jL8rgKiXlkyYmCwNaTIFwREv13cyCdqhD t/OTuqASiQba/PDs4UB75w1OCbaKAVXyQvJPAipEPgbwGCce6iLW4Gdd1mGiI/rAVBd5 kIPo805wJh+jNk+RVuhGv95GwU3Dmh3f+Wa1vho5GFG7fO3fbSm0QT6ifg+N7uT0iPWH zowQ== X-Gm-Message-State: AHQUAuZEhpBKKwiyGyFZV8CecWogpIoZAKhgTIi6yj9Rw3wY8oPoG3bA UfSyd+iJ3Y9UQbo0ozWnIl9pYQ== X-Google-Smtp-Source: AHgI3IYoW571J1Mbargry0dSLvhBvQdK5/NeOan6qv4n/bRuaI5i5jinvq0JPQkH5R/r3DLUERBiXg== X-Received: by 2002:a24:4648:: with SMTP id j69mr470647itb.56.1550522925849; Mon, 18 Feb 2019 12:48:45 -0800 (PST) Received: from google.com ([2620:15c:183:0:a0c3:519e:9276:fc96]) by smtp.gmail.com with ESMTPSA id d6sm5943432ioc.44.2019.02.18.12.48.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 18 Feb 2019 12:48:44 -0800 (PST) Date: Mon, 18 Feb 2019 13:48:42 -0700 From: Yu Zhao To: Will Deacon Cc: Catalin Marinas , "Aneesh Kumar K . V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Joel Fernandes , "Kirill A . Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, mark.rutland@arm.com Subject: Re: [PATCH] arm64: mm: enable per pmd page table lock Message-ID: <20190218204842.GA203083@google.com> References: <20190214211642.2200-1-yuzhao@google.com> <20190218151223.GB16091@fuggles.cambridge.arm.com> <20190218194938.GA184109@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190218194938.GA184109@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 18, 2019 at 12:49:38PM -0700, Yu Zhao wrote: > On Mon, Feb 18, 2019 at 03:12:23PM +0000, Will Deacon wrote: > > [+Mark] > > > > On Thu, Feb 14, 2019 at 02:16:42PM -0700, Yu Zhao wrote: > > > Switch from per mm_struct to per pmd page table lock by enabling > > > ARCH_ENABLE_SPLIT_PMD_PTLOCK. This provides better granularity for > > > large system. > > > > > > I'm not sure if there is contention on mm->page_table_lock. Given > > > the option comes at no cost (apart from initializing more spin > > > locks), why not enable it now. > > > > > > Signed-off-by: Yu Zhao > > > --- > > > arch/arm64/Kconfig | 3 +++ > > > arch/arm64/include/asm/pgalloc.h | 12 +++++++++++- > > > arch/arm64/include/asm/tlb.h | 5 ++++- > > > 3 files changed, 18 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > index a4168d366127..104325a1ffc3 100644 > > > --- a/arch/arm64/Kconfig > > > +++ b/arch/arm64/Kconfig > > > @@ -872,6 +872,9 @@ config ARCH_WANT_HUGE_PMD_SHARE > > > config ARCH_HAS_CACHE_LINE_SIZE > > > def_bool y > > > > > > +config ARCH_ENABLE_SPLIT_PMD_PTLOCK > > > + def_bool y > > > + > > > config SECCOMP > > > bool "Enable seccomp to safely compute untrusted bytecode" > > > ---help--- > > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h > > > index 52fa47c73bf0..dabba4b2c61f 100644 > > > --- a/arch/arm64/include/asm/pgalloc.h > > > +++ b/arch/arm64/include/asm/pgalloc.h > > > @@ -33,12 +33,22 @@ > > > > > > static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr) > > > { > > > - return (pmd_t *)__get_free_page(PGALLOC_GFP); > > > + struct page *page; > > > + > > > + page = alloc_page(PGALLOC_GFP); > > > + if (!page) > > > + return NULL; > > > + if (!pgtable_pmd_page_ctor(page)) { > > > + __free_page(page); > > > + return NULL; > > > + } > > > + return page_address(page); > > > > I'm a bit worried as to how this interacts with the page-table code in > > arch/arm64/mm/mmu.c when pgd_pgtable_alloc is used as the allocator. It > > looks like that currently always calls pgtable_page_ctor(), regardless of > > level. Do we now need a separate allocator function for the PMD level? > > Thanks for reminding me, I never noticed this. The short answer is > no. > > I guess pgtable_page_ctor() is used on all pud/pmd/pte entries > there because it's also compatible with pud, and pmd too without > this patch. So your concern is valid. Thanks again. > > Why my answer is no? Because I don't think the ctor matters for > pgd_pgtable_alloc(). The ctor is only required for userspace page > tables, and that's why we don't have it in pte_alloc_one_kernel(). > AFAICT, none of the pgds (efi_mm.pgd, tramp_pg_dir and init_mm.pgd) > pre-populated by pgd_pgtable_alloc() is. (I doubt we pre-populate > userspace page tables in any other arch). > > So to avoid future confusion, we might just remove the ctor from > pgd_pgtable_alloc(). I'm sorry. I've missed that we call apply_to_page_range() on efi_mm. The function does require the ctor. So we actually can't remove it. Though pgtable_page_ctor() also does the work adequately for pmd in terms of giving apply_to_page_range() what it requires, it would be more appropriate to use pgtable_pmd_page_ctor() instead (and not calling the ctor at all on pud). I could add this change prior to this patch, if it makes sense to you. Thanks.