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 9B4CCCD37B0 for ; Mon, 18 Sep 2023 12:12:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241853AbjIRMM3 (ORCPT ); Mon, 18 Sep 2023 08:12:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242045AbjIRMMR (ORCPT ); Mon, 18 Sep 2023 08:12:17 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 685EDFF for ; Mon, 18 Sep 2023 05:10:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695039041; h=from:from:reply-to: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=Di1DbymDlRuVr74aSXrGgFG7BrXnrGaVV92M3e3e9qg=; b=b9DZMAbgLkOfMF43YcBmdmkPFczxMu8nQf7lxaGKvMyl+qKZ5bedJiaUhGM35iynxoE7vC hXYBd3dwqXg46wO8W2TftYYHKMRIBUCtykmv2whNLoS8GCCVxuUitwl5KSF4xZpUhk2y+g HiqgikVBfYhEdu3Me4Sj7+CPgMyea8c= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-563--Q7N5OjAMgWciZst-nBeig-1; Mon, 18 Sep 2023 08:10:36 -0400 X-MC-Unique: -Q7N5OjAMgWciZst-nBeig-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5B05229AA3B0; Mon, 18 Sep 2023 12:10:35 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.114]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7A1D110D14C7; Mon, 18 Sep 2023 12:10:34 +0000 (UTC) Date: Mon, 18 Sep 2023 13:10:31 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Stephen Brennan Cc: qemu-devel@nongnu.org, linux-debuggers@vger.kernel.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Omar Sandoval , Thomas Huth Subject: Re: [PATCH v2 qemu 0/3] Allow dump-guest-memory to output standard kdump format Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20230914010315.945705-1-stephen.s.brennan@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230914010315.945705-1-stephen.s.brennan@oracle.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-debuggers@vger.kernel.org On Wed, Sep 13, 2023 at 06:03:12PM -0700, Stephen Brennan wrote: > Hello all, > > This is the second version of my patch series about the kdump format, > you can see the first version here [1]. > > The current output format for dump-guest-memory's kdump compressed > format is actually the "makedumpfile flattened" format. It was done > intentionally to allow the flexibility to write to non-seekable file > descriptors, like pipes [2], without using temporary files. Currently > libvirt uses this ability when VIR_DUMP_BYPASS_CACHE flag is set, to > avoid the dump process using page cache. The standard kdump output > format needs the page cache so that it can seek back and forth as part > of writing the dump file. > > So the default kdump dump format cannot be changed to the standard > format. This patch series adds the ability to use the standard format, > and adds a QMP / HMP argument to enable it. > > An open question for Daniel et al.: > > Would it be possible to make flattened the default only for libvirt? I > totally agree that this would be a bad backward incompatible change > there. But for QMP / HMP commands, I think using the standard, broadly > compatible format as the default is important for user friendliness. If > a user needs to know the difference between flavors of kdump formats > like the flattened format, in order to set the correct option, then > we've already lost. The default is 'elf' - any use of kdump formats is already an opt-in, and with the new kdump variants represented as enums, the user can just specify which they want explicitly. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|