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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 EE739C04ABB for ; Thu, 13 Sep 2018 10:50:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 93B7A20C0A for ; Thu, 13 Sep 2018 10:50:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="NVpWcAaf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 93B7A20C0A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727798AbeIMP7Y (ORCPT ); Thu, 13 Sep 2018 11:59:24 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:46304 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727082AbeIMP7Y (ORCPT ); Thu, 13 Sep 2018 11:59:24 -0400 Received: by mail-pg1-f193.google.com with SMTP id b129-v6so2564009pga.13 for ; Thu, 13 Sep 2018 03:50:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to:user-agent; bh=2YLO81sB6elElavA6ZjRN/hgCZR8EwrO1WMxSY84tlg=; b=NVpWcAaflFk3AwIYy/C+SCILM4PgfkChF7V32uZEjNJv+kg4QkNYyFJVMgNdb4UpDL QZ9exLS/8cO4LS5T6Iw+Bx8Jt9Gr1zW3qOdFVPN6MHmWWD//wSGd/BV52R8XRTz6Llar sl45KlSvNMDsv0pDuU38tEVo3wpLAErNlaLcy8Llyn3+8Oc/QfAiR9IS+fKmxtbKA0dG XWmgE8fUXOUnBJ1S2lLbREc4FJKOeiy/pDsdH43ApLwHaPQR8kkuO2LRtOdDwUzqz61s wc4QM7ZAepJzYg+Wrb2huqDNkyYRIcR7zdWk0106epNjMR0c7yIVz6+YxSVZ8+y0gfv+ 2iMw== 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 :mail-followup-to:references:mime-version:content-disposition :in-reply-to:user-agent; bh=2YLO81sB6elElavA6ZjRN/hgCZR8EwrO1WMxSY84tlg=; b=CA7RebZABw0NrqtrdMp6sLnosI+NL0iVBCwOiG9Nh/6BoY8Ha6WDBE7ZuEvBrZpu0b KtaujL7gV4nz/IImwjjzdl7zZnr45YwdjNoDGOnSW+vNtY3V7HReDUwHzrHLg6KOtJxP dNiIh1SkvcR2qD+Mo99MZaXDTEYfX4eb9Kqx7RioCoF2nI2W6zCyg8TJ4IQ1wheYoXs7 Z9J5zwBobOYILCBc1pO5Fz14juOro/wJurGcaAz1RGJVvx+ddga9JnjtAM2fe1LXbY8V V0K03/aIpibSBb76miUfl4QeKs5liq47kWpaLTKBQflRfqwGTEFmbQkLbDxe8mlgDjWm +0rA== X-Gm-Message-State: APzg51COqX9F97rfsqTJRtox/xW832b5LXnjs83T9OMMxrlDtmJ6hOSh CvkVrLUVqMZYTc/6Is7rP3Q= X-Google-Smtp-Source: ANB0VdYAvZO3gxH85SkkvqUnTxYue+4lKtRcVSZ9ruYg1f23UbjnipXT/BLicK0mAd18YL4XFGadFQ== X-Received: by 2002:a63:2043:: with SMTP id r3-v6mr6580391pgm.105.1536835829857; Thu, 13 Sep 2018 03:50:29 -0700 (PDT) Received: from toy ([104.192.108.9]) by smtp.gmail.com with ESMTPSA id b73-v6sm6175441pfj.93.2018.09.13.03.50.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 13 Sep 2018 03:50:29 -0700 (PDT) Date: Thu, 13 Sep 2018 18:50:21 +0800 From: Jun Yao To: James Morse Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH v4 5/6] arm64/mm: Populate the swapper_pg_dir by fixmap. Message-ID: <20180913105021.GA25870@toy> Mail-Followup-To: James Morse , linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org References: <20180822095432.12125-1-yaojun8558363@gmail.com> <20180822095432.12125-6-yaojun8558363@gmail.com> <2bf9b9d1-271c-f85e-5a98-0eb74f2fedd9@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2bf9b9d1-271c-f85e-5a98-0eb74f2fedd9@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, On Fri, Sep 07, 2018 at 10:58:22AM +0100, James Morse wrote: > On 22/08/18 10:54, Jun Yao wrote: > > WRITE_ONCE(*pmdp, pmd); > > dsb(ishst); > > } > > @@ -480,6 +511,19 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd) > > > > static inline void set_pud(pud_t *pudp, pud_t pud) > > { > > +#ifdef __PAGETABLE_PUD_FOLDED > > + if (in_swapper_pgdir(pudp)) { > > + pud_t *fixmap_pudp; > > + > > + spin_lock(&swapper_pgdir_lock); > > + fixmap_pudp = (pud_t *)pgd_set_fixmap(__pa(pudp)); > > I see this called 68 times during boot on a 64K/42bit-VA, 65 of which appear to > be during paging_init(). What do you think to keeping paging_init()s use of the > pgd fixmap for swapper_pg_dir, deliberately to skip the in_swapper_pgdir() test > during paging_init()? I find that the __create_pgd_mapping() is used to set up the page table during paging_init(). And there are six functions calling it with different pgdps: update_mapping_prot() init_mm.pgd(swapper_pg_dir) create_mapping_noalloc() init_mm.pgd(swapper_pg_dir) __map_memblock() pgdp(swapper_pg_dir) map_kernel_segment() pgdp(swapper_pg_dir) create_pgd_mapping() !(init_mm.pgd) map_entry_trampoline() tramp_pg_dir In order to skip the in_swapper_pgdir() test during paging_init(), We need a way to determine if we are currently in paging_init(). The way I can think of is to create a function similar to __create_pgd_mapping(). And it is used to create the page table during paging_init(). It differs from the __create_pgd_mapping() only in that it calls p?d_populate_without_test(). However, in this way, I'm worried that I am reinventing the wheel. Thanks, Jun