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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F14DBC43334 for ; Tue, 12 Jul 2022 04:24:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229518AbiGLEYB (ORCPT ); Tue, 12 Jul 2022 00:24:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229572AbiGLEXx (ORCPT ); Tue, 12 Jul 2022 00:23:53 -0400 Received: from sender4-op-o14.zoho.com (sender4-op-o14.zoho.com [136.143.188.14]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D08B1A385; Mon, 11 Jul 2022 21:23:48 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1657599818; cv=none; d=zohomail.com; s=zohoarc; b=lYy2koBE8WQhh9HsLuGC8iyWBoYe4JjtACHNpzHZH99GbFxPjOIcaR4+kATOZVHTaT/RW42it+SRCDKNO7SqfnxQBf9Lj/vwWsHU3U4tzEM5RZGSk2zShNWfpNA9mINgA1Lmhu5fid3g9iEp7HsMNPgJC9TZ+daMGh1bMf1xKUQ= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1657599818; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:To; bh=AYZhl4Tgx5eXsw054d7yEPiQv66vkg0JPurDrzFEdv0=; b=Hdd/Ff0B9wGPEc5WEtB/YnzgqXvJFPIGnI4JP9rkFCd4T95isyhFcaOJjSqFkcNL6ywomEXaiOo1rFVaZuXe8OkwjgIwOB4G9PWOSMcToXV4ptjNuDGw/mMJELLqd/JxYig3dn1HXJULFgYa5JSv/EK744xmc+Tlo9HK72p2NbQ= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=linux.beauty; spf=pass smtp.mailfrom=me@linux.beauty; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1657599818; s=zmail; d=linux.beauty; i=me@linux.beauty; h=Date:Date:From:From:To:To:Cc:Cc:Message-ID:In-Reply-To:References:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=AYZhl4Tgx5eXsw054d7yEPiQv66vkg0JPurDrzFEdv0=; b=V5rJcwOxbzzZIC4sbkyYEN3bVl2QRlwZdwcw8n/JqG1DQE7qXaM9iEx4PRnRF5Rg jBhigsObcYHRzKwGoCtW9bFxFhuE+jbM+bv+RYhGpXYtiF5Xk45KmebxhDRoVOF1m1W 6KEa90MDYHaWYOyAjS1Tk2dCMOh0jcVeoYHUV6q8= Received: from mail.zoho.com by mx.zohomail.com with SMTP id 1657599816384969.9914766883284; Mon, 11 Jul 2022 21:23:36 -0700 (PDT) Date: Tue, 12 Jul 2022 12:23:36 +0800 From: Li Chen To: "David Hildenbrand" Cc: "Catalin Marinas" , "Will Deacon" , "Rob Herring" , "Frank Rowand" , "Andrew Morton" , "Li Chen" , "linux-arm-kernel" , "linux-kernel" , "devicetree" , "linux-mm" Message-ID: <181f0a5f2a5.cf94ce78513585.4158910057206462182@linux.beauty> In-Reply-To: References: <20220711122459.13773-1-me@linux.beauty> <20220711122459.13773-3-me@linux.beauty> Subject: Re: [PATCH 2/4] mm/sparse: skip no-map memblock check when fill_subsection_map MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Importance: Medium User-Agent: Zoho Mail X-Mailer: Zoho Mail Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi David, ---- On Mon, 11 Jul 2022 22:53:36 +0800 David Hildenbrand wrote --- > On 11.07.22 14:24, Li Chen wrote: > > From: Li Chen > > > > When mhp use sparse_add_section, don't check no-map region, > > so that to allow no-map reserved memory to get struct page > > support. > > > > Signed-off-by: Li Chen > > Change-Id: I0d2673cec1b66adf695251037a00c240976b226f > > --- > > mm/sparse.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/mm/sparse.c b/mm/sparse.c > > index 120bc8ea5293..a29cd1e7014f 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -690,7 +690,9 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages) > > > > if (bitmap_empty(map, SUBSECTIONS_PER_SECTION)) > > rc = -EINVAL; > > - else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION)) > > + else if (memblock_is_map_memory(PFN_PHYS(pfn)) && > > + bitmap_intersects(map, subsection_map, > > + SUBSECTIONS_PER_SECTION)) > > rc = -EEXIST; > > else > > bitmap_or(subsection_map, map, subsection_map, > > I'm not sure I follow completely what you are trying to achieve. But if > you have to add memblock hacks into mm/sparse.c you're most probably > doing something wrong. > > Please explain why that change is necessary, and why it is safe. In the current sparse memory model, free_area_init will insert all memblock.memory into subsection_map and no-map rmem is also a memblock.memory. So, without this change, fill_subsection_map will return -EEXIST. I would say it's not a good idea to insert no-map memblock into subsection_map, and I have no idea why sparse do this. So, I simply skip no-map region here. As for safety: 1. The caller of fill_subsection_map are mhp and *_memremap_pages functions, no-map regions are not related to them, so existing codes won't be broken. 2. This change doesn't change memblock and subsection_map. > > If the subsection map already spans memory (iow, subsection map is set) > you intend to add, then something already added memory in that range? No matter with or without this patch, fill_subsection_map will always return -EEXIST for mapped memory, so that's not a problem. The key point here is I allowed no-map region to pass the check and didn't change anything to the mapped region. Regards, Li