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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 3D553C433DB for ; Tue, 2 Feb 2021 13:22:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0209764F4A for ; Tue, 2 Feb 2021 13:22:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232321AbhBBNWS (ORCPT ); Tue, 2 Feb 2021 08:22:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:36556 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231670AbhBBNWM (ORCPT ); Tue, 2 Feb 2021 08:22:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612272046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=o/60teeEdPgl7qYScyFSquW5ice+PAw0Sozx+qSY1fA=; b=LnLqifO/BW3hu/esX4liPTQwI+zyfWm9506ROU0OQ+3iuwwRBt8r8OmDjTPJtzskEpWV0F VSUgRqnjc5aytUH0qbw93ObotFrziy2tePizgeCLP4OL+g43MqFKPSGG5nB07pmc4CsYdf N4OijV80TLtUndV5LXG/woA6LrAIEyA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-536-Rw45LFaRNMiiDaV9Q4vU3w-1; Tue, 02 Feb 2021 08:20:42 -0500 X-MC-Unique: Rw45LFaRNMiiDaV9Q4vU3w-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ABBFC801817; Tue, 2 Feb 2021 13:20:40 +0000 (UTC) Received: from [10.36.114.148] (ovpn-114-148.ams2.redhat.com [10.36.114.148]) by smtp.corp.redhat.com (Postfix) with ESMTP id 313465C1CF; Tue, 2 Feb 2021 13:20:37 +0000 (UTC) To: Oscar Salvador , Andrew Morton Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210202112450.11932-1-osalvador@suse.de> <20210202112450.11932-2-osalvador@suse.de> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH 1/2] x86/vmemmap: Remove !PAGE_ALIGNED case in remove_pte_table Message-ID: <1d8ca669-6c92-4692-b2c7-1bfaa6f9707e@redhat.com> Date: Tue, 2 Feb 2021 14:20:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20210202112450.11932-2-osalvador@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > @@ -962,7 +962,6 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, > { > unsigned long next, pages = 0; > pte_t *pte; > - void *page_addr; > phys_addr_t phys_addr; > > pte = pte_start + pte_index(addr); > @@ -983,42 +982,19 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, > if (phys_addr < (phys_addr_t)0x40000000) > return; > > - if (PAGE_ALIGNED(addr) && PAGE_ALIGNED(next)) { > - /* > - * Do not free direct mapping pages since they were > - * freed when offlining, or simplely not in use. > - */ > - if (!direct) > - free_pagetable(pte_page(*pte), 0); > - > - spin_lock(&init_mm.page_table_lock); > - pte_clear(&init_mm, addr, pte); > - spin_unlock(&init_mm.page_table_lock); > - > - /* For non-direct mapping, pages means nothing. */ > - pages++; > - } else { > - /* > - * If we are here, we are freeing vmemmap pages since > - * direct mapped memory ranges to be freed are aligned. > - * > - * If we are not removing the whole page, it means > - * other page structs in this page are being used and > - * we canot remove them. So fill the unused page_structs > - * with 0xFD, and remove the page when it is wholly > - * filled with 0xFD. > - */ > - memset((void *)addr, PAGE_INUSE, next - addr); > + /* > + * Do not free direct mapping pages since they were > + * freed when offlining, or simplely not in use. > + */ s/simplely/simply/ (I know, not your fault :) ) However, that comment is highly confusing. There is nothing to free in case of the a direct mapping; we never allocated anything. That's how a direct map works. I'd just get rid of the comment completely - we also don't have one at the other "if (!direct)" places. (side note: all this freeing before unmapping looks very weird, but at least we should have valid accesses anymore) > + if (!direct) > + free_pagetable(pte_page(*pte), 0); [...] > { > + /* > + * See comment in vmemmap_populate(). > + */ I'd drop this comment ... > + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); > + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); > + > remove_pagetable(start, end, false, altmap); > } > > @@ -1556,6 +1538,15 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, > { > int err; > > + /* > + * __populate_section_memmap enforces the range to be added to be > + * PMD aligned. Therefore we can be sure that, as long as the > + * struct page size is multiple of 8, the vmemmap range will be > + * PAGE aligned. > + */ ... and this comment, moving the details into the patch description. The commit should be easy to detect using git blame in case anybody wonders why. > + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); > + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); > + > if (end - start < PAGES_PER_SECTION * sizeof(struct page)) > err = vmemmap_populate_basepages(start, end, node, NULL); > else if (boot_cpu_has(X86_FEATURE_PSE)) > Apart from that looks good, thanks! -- Thanks, David / dhildenb