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 1B885C25B74 for ; Tue, 21 May 2024 08:20:59 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s9KjS-0000d5-9G; Tue, 21 May 2024 04:20:26 -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 1s9KjQ-0000ck-Pu for qemu-devel@nongnu.org; Tue, 21 May 2024 04:20:24 -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 1s9KjO-00046Q-Pk for qemu-devel@nongnu.org; Tue, 21 May 2024 04:20:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1716279618; 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=FNDnqfzG5OQOeeLKdR90CnrFJYqiPUYj5+DdXbdcMn8=; b=jA5JA1n6aSe4GOY/b9CG3KMET/SDhLp+BmVAVlQ/CTcDiDySsSCdEbWc6XlDY2YbiWSP2y ahojmHwSjjDONsCbpbD0l0tFW1RaXwTJ7H5EpJOP/pOUvOZy/nNPBNu77yoosOAUQDf6IK 8q8nRFr5djQ2n4/PcU8ZtKisB2cL+pQ= 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-45-OE-XWr3CM02FiZn79kdKUA-1; Tue, 21 May 2024 04:20:11 -0400 X-MC-Unique: OE-XWr3CM02FiZn79kdKUA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (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 88659185AD2C; Tue, 21 May 2024 08:20:10 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.69]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 631E21C09480; Tue, 21 May 2024 08:20:08 +0000 (UTC) Date: Tue, 21 May 2024 09:20:06 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= 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 , Markus Armbruster Subject: Re: [PATCH V1 20/26] migration: cpr-exec mode Message-ID: References: <1714406135-451286-1-git-send-email-steven.sistare@oracle.com> <1714406135-451286-21-git-send-email-steven.sistare@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1714406135-451286-21-git-send-email-steven.sistare@oracle.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Apr 29, 2024 at 08:55:29AM -0700, Steve Sistare wrote: > 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 > --- > include/migration/cpr.h | 14 +++++ > include/migration/misc.h | 3 ++ > migration/cpr.c | 131 +++++++++++++++++++++++++++++++++++++++++++++++ > migration/meson.build | 1 + > migration/migration.c | 21 ++++++++ > migration/migration.h | 5 +- > migration/ram.c | 1 + > qapi/migration.json | 30 ++++++++++- > system/physmem.c | 2 + > system/vl.c | 4 ++ > 10 files changed, 210 insertions(+), 2 deletions(-) > create mode 100644 include/migration/cpr.h > create mode 100644 migration/cpr.c > > + > +void cpr_exec(char **argv) > +{ > + MigrationState *s = migrate_get_current(); > + Error *err = NULL; > + > + /* > + * Clear the close-on-exec flag for all preserved fd's. We cannot do so > + * earlier because they should not persist across miscellaneous fork and > + * exec calls that are performed during normal operation. > + */ > + cpr_preserve_fds(); > + > + execvp(argv[0], argv); > + > + error_setg_errno(&err, errno, "execvp %s failed", argv[0]); This is where you could give a more direct message about the sandbox. eg if (errno == EPERM) { error_append_hint("sandbox is blocking ability to exec"); } this would also benefit the case where an external sandbox is used, rather than qemu's built-in sandbox. > + error_report_err(err); > + migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED); > + migrate_set_error(s, err); > + migration_precreate_unsave(); > +} 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 :|