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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DEC7C433FE for ; Mon, 4 Oct 2021 14:32:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F15C361373 for ; Mon, 4 Oct 2021 14:32:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234379AbhJDOe2 (ORCPT ); Mon, 4 Oct 2021 10:34:28 -0400 Received: from out2.migadu.com ([188.165.223.204]:61281 "EHLO out2.migadu.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234021AbhJDOe1 (ORCPT ); Mon, 4 Oct 2021 10:34:27 -0400 Date: Mon, 4 Oct 2021 23:32:28 +0900 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1633357957; 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: in-reply-to:in-reply-to:references:references; bh=sqfgVz/9I9K4KamPvNycNExje+swH63ObdWWIwX9lL0=; b=ab9jun9Daj2WzTS+9xxyU1duapIjcVsi7r15EhDxVhJlyYsph6hq5CgjfP2mcN/6r8vXhh JMzR+JMq7ofPAFz/Y39rIlxlZUH96f4qs4g9xizVi3KtC/4AuKxmBKIGiqBs0pZkDW6ACL JgtcZqPUxwwVZOrPYEHfSp227Xv38U8= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Naoya Horiguchi To: David Hildenbrand Cc: linux-mm@kvack.org, Andrew Morton , Alistair Popple , Peter Xu , Mike Kravetz , Konstantin Khlebnikov , Bin Wang , Yang Shi , Naoya Horiguchi , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm, pagemap: expose hwpoison entry Message-ID: <20211004143228.GA1545442@u2004> References: <20211004115001.1544259-1-naoya.horiguchi@linux.dev> <258d0ddb-6c82-0c95-a15e-b085b59d2142@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <258d0ddb-6c82-0c95-a15e-b085b59d2142@redhat.com> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: naoya.horiguchi@linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 04, 2021 at 01:55:30PM +0200, David Hildenbrand wrote: > On 04.10.21 13:50, Naoya Horiguchi wrote: > > From: Naoya Horiguchi > > > > A hwpoison entry is a non-present page table entry to report > > memory error events to userspace. If we have an easy way to know > > which processes have hwpoison entries, that might be useful for > > user processes to take proper actions. But we don't have it now. > > So make pagemap interface expose hwpoison entries to userspace. > > Noting that this is only a way to inspect hwpoison set for private anonymous > memory. You cannot really identify anything related to shared memory. > > Do you also handle private hugetlb pages? I think yes. As long as hugepages are mmap()ed, we should be able to identify them with hwpoison entry (even if used via private/shared mapping). > > > > > Hwpoison entry for hugepage is also exposed by this patch. The below > > example shows how pagemap is visible in the case where a memory error > > hit a hugepage mapped to a process. > > > > $ ./page-types --no-summary --pid $PID --raw --list --addr 0x700000000+0x400 > > voffset offset len flags > > 700000000 12fa00 1 ___U_______Ma__H_G_________________f_______1 > > 700000001 12fa01 1ff ___________Ma___TG_________________f_______1 > > 700000200 12f800 1 __________B________X_______________f______w_ > > 700000201 12f801 1 ___________________X_______________f______w_ // memory failure hit this page > > 700000202 12f802 1fe __________B________X_______________f______w_ > > > > The entries with both of "X" flag (hwpoison flag) and "w" flag (swap > > flag) are considered as hwpoison entries. So all pages in 2MB range > > are inaccessible from the process. We can get actual error location > > by page-types in physical address mode. > > > > $ ./page-types --no-summary --addr 0x12f800+0x200 --raw --list > > offset len flags > > 12f800 1 __________B_________________________________ > > 12f801 1 ___________________X________________________ > > 12f802 1fe __________B_________________________________ > > > > Signed-off-by: Naoya Horiguchi > > --- > > fs/proc/task_mmu.c | 41 ++++++++++++++++++++++++++++++++--------- > > include/linux/swapops.h | 13 +++++++++++++ > > tools/vm/page-types.c | 7 ++++++- > > 3 files changed, 51 insertions(+), 10 deletions(-) > > > Please also update the documentation located at > > Documentation/admin-guide/mm/pagemap.rst I will do this in the next post. Thanks, Naoya Horigcuhi