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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A273AC4345F for ; Thu, 2 May 2024 12:25:04 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s2VTm-000390-IU; Thu, 02 May 2024 08:24:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s2VTk-00038V-CY for qemu-devel@nongnu.org; Thu, 02 May 2024 08:24:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s2VTi-0002k2-EI for qemu-devel@nongnu.org; Thu, 02 May 2024 08:24:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1714652637; 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=xMQVy7oJq8SdNlUsNwqEI1Z9p1RrdR2ZtYybwfpuUg0=; b=RAo5t+Z7S65fqyENZRgpjA39rUilTIuY+9dFq/TqgA5Rlfl7CbD67Rb0mAlFO43BZ3+7Cq 6tvWjtvhv1+sG7cPB+3fq+Jg9Nne/+fkuAg5OKDiTfdayKD9Org64F4pTcaqPy1ZpJodYs 8DNZ9N/O2bFPu4t2sR1YrhDjeLLStts= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-461-c34bWZKJN1Sunee46VzyBw-1; Thu, 02 May 2024 08:23:56 -0400 X-MC-Unique: c34bWZKJN1Sunee46VzyBw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F1FB38021A4; Thu, 2 May 2024 12:23:55 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B74EE40B4979; Thu, 2 May 2024 12:23:55 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id C6C2A21E6811; Thu, 2 May 2024 14:23:54 +0200 (CEST) From: Markus Armbruster To: Steve Sistare Cc: qemu-devel@nongnu.org, Peter Xu , Fabiano Rosas , David Hildenbrand , Igor Mammedov , Eduardo Habkost , Marcel Apfelbaum , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" Subject: Re: [PATCH V1 20/26] migration: cpr-exec mode In-Reply-To: <1714406135-451286-21-git-send-email-steven.sistare@oracle.com> (Steve Sistare's message of "Mon, 29 Apr 2024 08:55:29 -0700") References: <1714406135-451286-1-git-send-email-steven.sistare@oracle.com> <1714406135-451286-21-git-send-email-steven.sistare@oracle.com> Date: Thu, 02 May 2024 14:23:54 +0200 Message-ID: <87bk5o7679.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.476, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Steve Sistare writes: > Add the cpr-exec migration mode. Usage: > qemu-system-$arch -machine memfd-alloc=on ... > migrate_set_parameter mode cpr-exec > migrate_set_parameter cpr-exec-args \ > ... -incoming > migrate -d > > The migrate command stops the VM, saves state to the URI, > directly exec's a new version of QEMU on the same host, > replacing the original process while retaining its PID, and > loads state from the URI. Guest RAM is preserved in place, > albeit with new virtual addresses. > > Arguments for the new QEMU process are taken from the > @cpr-exec-args parameter. The first argument should be the > path of a new QEMU binary, or a prefix command that exec's the > new QEMU binary. > > Because old QEMU terminates when new QEMU starts, one cannot > stream data between the two, so the URI must be a type, such as > a file, that reads all data before old QEMU exits. > > Memory backend objects must have the share=on attribute, and > must be mmap'able in the new QEMU process. For example, > memory-backend-file is acceptable, but memory-backend-ram is > not. > > The VM must be started with the '-machine memfd-alloc=on' > option. This causes implicit ram blocks (those not explicitly > described by a memory-backend object) to be allocated by > mmap'ing a memfd. Examples include VGA, ROM, and even guest > RAM when it is specified without a memory-backend object. > > The implementation saves precreate vmstate at the end of normal > migration in migrate_fd_cleanup, and tells the main loop to call > cpr_exec. Incoming qemu loads preceate state early, before objects > are created. The memfds are kept open across exec by clearing the > close-on-exec flag, their values are saved in precreate vmstate, > and they are mmap'd in new qemu. > > Note that the memfd-alloc option is not related to memory-backend-memfd. > Later patches add support for memory-backend-memfd, and for additional > devices, including vfio, chardev, and more. > > Signed-off-by: Steve Sistare [...] > diff --git a/qapi/migration.json b/qapi/migration.json > index 49710e7..7c5f45f 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -665,9 +665,37 @@ > # or COLO. > # > # (since 8.2) > +# > +# @cpr-exec: The migrate command stops the VM, saves state to the URI, > +# directly exec's a new version of QEMU on the same host, > +# replacing the original process while retaining its PID, and > +# loads state from the URI. Guest RAM is preserved in place, > +# albeit with new virtual addresses. Do you mean the virtual addresses of guest RAM may differ betwen old and new QEMU process? > +# > +# Arguments for the new QEMU process are taken from the > +# @cpr-exec-args parameter. The first argument should be the > +# path of a new QEMU binary, or a prefix command that exec's the > +# new QEMU binary. What's a "prefix command"? A wrapper script, perhaps? > +# > +# Because old QEMU terminates when new QEMU starts, one cannot > +# stream data between the two, so the URI must be a type, such as > +# a file, that reads all data before old QEMU exits. What happens when you specify a URI that doesn't? > +# > +# Memory backend objects must have the share=on attribute, and > +# must be mmap'able in the new QEMU process. For example, > +# memory-backend-file is acceptable, but memory-backend-ram is > +# not. > +# > +# The VM must be started with the '-machine memfd-alloc=on' What happens when you don't? > +# option. This causes implicit ram blocks -- those not explicitly > +# described by a memory-backend object -- to be allocated by > +# mmap'ing a memfd. Examples include VGA, ROM, and even guest > +# RAM when it is specified without a memory-backend object. > +# > +# (since 9.1) > ## > { 'enum': 'MigMode', > - 'data': [ 'normal', 'cpr-reboot' ] } > + 'data': [ 'normal', 'cpr-reboot', 'cpr-exec' ] } > > ## > # @ZeroPageDetection: [...]