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,URIBL_BLOCKED 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 B7FC3C43441 for ; Wed, 21 Nov 2018 01:59:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AA882146D for ; Wed, 21 Nov 2018 01:59:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8AA882146D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S1726792AbeKUMcL (ORCPT ); Wed, 21 Nov 2018 07:32:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55610 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725913AbeKUMcK (ORCPT ); Wed, 21 Nov 2018 07:32:10 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B931FC059B6F; Wed, 21 Nov 2018 01:59:55 +0000 (UTC) Received: from redhat.com (ovpn-120-136.rdu2.redhat.com [10.10.120.136]) by smtp.corp.redhat.com (Postfix) with SMTP id BB6825D75D; Wed, 21 Nov 2018 01:59:44 +0000 (UTC) Date: Tue, 20 Nov 2018 20:59:43 -0500 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, devel@linuxdriverproject.org, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org, xen-devel@lists.xenproject.org, kexec-ml , pv-drivers@vmware.com, Andrew Morton , Dave Young , "Kirill A. Shutemov" , Baoquan He , Omar Sandoval , Arnd Bergmann , Matthew Wilcox , Michal Hocko , Lianbo Jiang , Borislav Petkov , Kazuhito Hagio Subject: Re: [PATCH v1 3/8] kexec: export PG_offline to VMCOREINFO Message-ID: <20181120205822-mutt-send-email-mst@kernel.org> References: <20181119101616.8901-1-david@redhat.com> <20181119101616.8901-4-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181119101616.8901-4-david@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 21 Nov 2018 01:59:56 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 19, 2018 at 11:16:11AM +0100, David Hildenbrand wrote: > Right now, pages inflated as part of a balloon driver will be dumped > by dump tools like makedumpfile. While XEN is able to check in the > crash kernel whether a certain pfn is actuall backed by memory in the > hypervisor (see xen_oldmem_pfn_is_ram) and optimize this case, dumps of > other balloon inflated memory will essentially result in zero pages getting > allocated by the hypervisor and the dump getting filled with this data. > > The allocation and reading of zero pages can directly be avoided if a > dumping tool could know which pages only contain stale information not to > be dumped. > > We now have PG_offline which can be (and already is by virtio-balloon) > used for marking pages as logically offline. Follow up patches will > make use of this flag also in other balloon implementations. > > Let's export PG_offline via PAGE_OFFLINE_MAPCOUNT_VALUE, so > makedumpfile can directly skip pages that are logically offline and the > content therefore stale. > > Please note that this is also helpful for a problem we were seeing under > Hyper-V: Dumping logically offline memory (pages kept fake offline while > onlining a section via online_page_callback) would under some condicions > result in a kernel panic when dumping them. > > Cc: Andrew Morton > Cc: Dave Young > Cc: "Kirill A. Shutemov" > Cc: Baoquan He > Cc: Omar Sandoval > Cc: Arnd Bergmann > Cc: Matthew Wilcox > Cc: Michal Hocko > Cc: "Michael S. Tsirkin" > Cc: Lianbo Jiang > Cc: Borislav Petkov > Cc: Kazuhito Hagio > Signed-off-by: David Hildenbrand Acked-by: Michael S. Tsirkin > --- > kernel/crash_core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 933cb3e45b98..093c9f917ed0 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -464,6 +464,8 @@ static int __init crash_save_vmcoreinfo_init(void) > VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE); > #ifdef CONFIG_HUGETLB_PAGE > VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR); > +#define PAGE_OFFLINE_MAPCOUNT_VALUE (~PG_offline) > + VMCOREINFO_NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE); > #endif > > arch_crash_save_vmcoreinfo(); > -- > 2.17.2