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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 98FFEECE58E for ; Tue, 15 Oct 2019 08:35:56 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6894C2089C for ; Tue, 15 Oct 2019 08:35:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6894C2089C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37410 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iKIJ9-00070f-BF for qemu-devel@archiver.kernel.org; Tue, 15 Oct 2019 04:35:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58442) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iKIIM-0006JH-6E for qemu-devel@nongnu.org; Tue, 15 Oct 2019 04:35:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iKIIK-0004AN-Tn for qemu-devel@nongnu.org; Tue, 15 Oct 2019 04:35:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52016) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iKIIK-00049l-OS for qemu-devel@nongnu.org; Tue, 15 Oct 2019 04:35:04 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E0CA98E1CE7 for ; Tue, 15 Oct 2019 08:35:02 +0000 (UTC) Received: from redhat.com (unknown [10.36.118.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 59921608A5; Tue, 15 Oct 2019 08:34:59 +0000 (UTC) From: Juan Quintela To: Peter Xu Subject: Re: [PATCH 1/2] migration: Boost SaveStateEntry.instance_id to 64 bits In-Reply-To: <20191015075444.10955-2-peterx@redhat.com> (Peter Xu's message of "Tue, 15 Oct 2019 15:54:43 +0800") References: <20191015075444.10955-1-peterx@redhat.com> <20191015075444.10955-2-peterx@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) Date: Tue, 15 Oct 2019 10:34:57 +0200 Message-ID: <87tv8aqudq.fsf@trasno.org> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.69]); Tue, 15 Oct 2019 08:35:02 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: quintela@redhat.com Cc: Paolo Bonzini , "Dr . David Alan Gilbert" , qemu-devel@nongnu.org, Eduardo Habkost , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Peter Xu wrote: > It was "int" and used as 32bits fields (see save_section_header()). > It's unsafe already because sizeof(int) could be 2 on i386, i386 is 32bits, so int is 32bits O:-) I really hope that we would never, ever, need a 64bits instance id. It would mean that we have more than 2.000.000.000 objects of the same type, no? I am pretty sure than in 16bits platforms we have other problems than insntance_id (namely that we don't have enough memory). >I think. > So at least uint32_t would suite more. While it also uses "-1" as a > placeholder of "we want to generate the instance ID automatically". > Hence a more proper value should be int64_t. > > This will start to be useful after next patch in which we can start to > convert a real uint32_t value as instance ID. Later, Juan.