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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 D90EDC43381 for ; Mon, 11 Mar 2019 12:57:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5A362075C for ; Mon, 11 Mar 2019 12:57:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727334AbfCKM5b (ORCPT ); Mon, 11 Mar 2019 08:57:31 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:53848 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726605AbfCKM5a (ORCPT ); Mon, 11 Mar 2019 08:57:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F178FA78; Mon, 11 Mar 2019 05:57:29 -0700 (PDT) Received: from [10.163.1.86] (unknown [10.163.1.86]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 058B03F703; Mon, 11 Mar 2019 05:57:22 -0700 (PDT) Subject: Re: [PATCH v3 3/3] arm64: mm: enable per pmd page table lock To: Mark Rutland , Yu Zhao Cc: Catalin Marinas , Will Deacon , "Aneesh Kumar K . V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Joel Fernandes , "Kirill A . Shutemov" , Ard Biesheuvel , Chintan Pandya , Jun Yao , Laura Abbott , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org References: <20190218231319.178224-1-yuzhao@google.com> <20190310011906.254635-1-yuzhao@google.com> <20190310011906.254635-3-yuzhao@google.com> <20190311121147.GA23361@lakrids.cambridge.arm.com> From: Anshuman Khandual Message-ID: Date: Mon, 11 Mar 2019 18:27:19 +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: <20190311121147.GA23361@lakrids.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/11/2019 05:42 PM, Mark Rutland wrote: > Hi, > > On Sat, Mar 09, 2019 at 06:19:06PM -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. >> >> We only do so when pmd is not folded, so we don't mistakenly call >> pgtable_pmd_page_ctor() on pud or p4d in pgd_pgtable_alloc(). (We >> check shift against PMD_SHIFT, which is same as PUD_SHIFT when pmd >> is folded). > > Just to check, I take it pgtable_pmd_page_ctor() is now a NOP when the > PMD is folded, and this last paragraph is stale? > >> 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 cfbf307d6dc4..a3b1b789f766 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 if PGTABLE_LEVELS > 2 >> + >> 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); >> } >> >> static inline void pmd_free(struct mm_struct *mm, pmd_t *pmdp) >> { >> BUG_ON((unsigned long)pmdp & (PAGE_SIZE-1)); >> + pgtable_pmd_page_dtor(virt_to_page(pmdp)); >> free_page((unsigned long)pmdp); >> } > > It looks like arm64's existing stage-2 code is inconsistent across > alloc/free, and IIUC this change might turn that into a real problem. > Currently we allocate all levels of stage-2 table with > __get_free_page(), but free them with p?d_free(). We always miss the > ctor and always use the dtor. > > Other than that, this patch looks fine to me, but I'd feel more > comfortable if we could first fix the stage-2 code to free those stage-2 > tables without invoking the dtor. Thats right. I have already highlighted this problem. > > Anshuman, IIRC you had a patch to fix the stage-2 code to not invoke the > dtors. If so, could you please post that so that we could take it as a > preparatory patch for this series? Sure I can after fixing PTE level pte_free_kernel/__free_page which I had missed in V2. https://www.spinics.net/lists/arm-kernel/msg710118.html 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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS 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 CC11AC43381 for ; Mon, 11 Mar 2019 12:57:38 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8C7062084F for ; Mon, 11 Mar 2019 12:57:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="SINfK4Lc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C7062084F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=eokQqaogV9ZJnuMclMWvD71dXHrjZ4Ehg4lZB8ut//E=; b=SINfK4Lc0Ni5tr MEz/TYoOcimbxiKQGtbCzgXVI/zsC2u5+dJWW4H6SSBG8OdD7lKTLjMkEMXIrgrwF/Yx9K0Jj8CR9 xI5CF5ko38S8//Xq/Ge2/CuzG4eTcZZwvAL9/JNg90lt/m0kUqZDIYUNFbByZYYHvZH4xKZDTINpf v/1eirc7PwGY/IHw1n7vzDqrv0slZst0PX6ttZQTO3/la+afv9VPKnPh/eW8HTwwEI7W0xuTWjgQ2 G4LTRVTW4lGY5UbnjNLfn8SMfHLjUmTn6XVq4cXjygQ656C2ecJ7zMqCh9b0cSgHlkDuKnTgWJMjQ OmXQuPutYM9aJZrVyDVQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3KUn-00064z-RM; Mon, 11 Mar 2019 12:57:33 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3KUk-00064W-S9 for linux-arm-kernel@lists.infradead.org; Mon, 11 Mar 2019 12:57:32 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F178FA78; Mon, 11 Mar 2019 05:57:29 -0700 (PDT) Received: from [10.163.1.86] (unknown [10.163.1.86]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 058B03F703; Mon, 11 Mar 2019 05:57:22 -0700 (PDT) Subject: Re: [PATCH v3 3/3] arm64: mm: enable per pmd page table lock To: Mark Rutland , Yu Zhao References: <20190218231319.178224-1-yuzhao@google.com> <20190310011906.254635-1-yuzhao@google.com> <20190310011906.254635-3-yuzhao@google.com> <20190311121147.GA23361@lakrids.cambridge.arm.com> From: Anshuman Khandual Message-ID: Date: Mon, 11 Mar 2019 18:27:19 +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: <20190311121147.GA23361@lakrids.cambridge.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190311_055730_921514_3677444B X-CRM114-Status: GOOD ( 29.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Nick Piggin , Jun Yao , linux-mm@kvack.org, "Aneesh Kumar K . V" , Chintan Pandya , Joel Fernandes , "Kirill A . Shutemov" , Andrew Morton , Laura Abbott , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 03/11/2019 05:42 PM, Mark Rutland wrote: > Hi, > > On Sat, Mar 09, 2019 at 06:19:06PM -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. >> >> We only do so when pmd is not folded, so we don't mistakenly call >> pgtable_pmd_page_ctor() on pud or p4d in pgd_pgtable_alloc(). (We >> check shift against PMD_SHIFT, which is same as PUD_SHIFT when pmd >> is folded). > > Just to check, I take it pgtable_pmd_page_ctor() is now a NOP when the > PMD is folded, and this last paragraph is stale? > >> 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 cfbf307d6dc4..a3b1b789f766 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 if PGTABLE_LEVELS > 2 >> + >> 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); >> } >> >> static inline void pmd_free(struct mm_struct *mm, pmd_t *pmdp) >> { >> BUG_ON((unsigned long)pmdp & (PAGE_SIZE-1)); >> + pgtable_pmd_page_dtor(virt_to_page(pmdp)); >> free_page((unsigned long)pmdp); >> } > > It looks like arm64's existing stage-2 code is inconsistent across > alloc/free, and IIUC this change might turn that into a real problem. > Currently we allocate all levels of stage-2 table with > __get_free_page(), but free them with p?d_free(). We always miss the > ctor and always use the dtor. > > Other than that, this patch looks fine to me, but I'd feel more > comfortable if we could first fix the stage-2 code to free those stage-2 > tables without invoking the dtor. Thats right. I have already highlighted this problem. > > Anshuman, IIRC you had a patch to fix the stage-2 code to not invoke the > dtors. If so, could you please post that so that we could take it as a > preparatory patch for this series? Sure I can after fixing PTE level pte_free_kernel/__free_page which I had missed in V2. https://www.spinics.net/lists/arm-kernel/msg710118.html _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel