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 45795C32771 for ; Wed, 28 Sep 2022 18:12:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234674AbiI1SMY (ORCPT ); Wed, 28 Sep 2022 14:12:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234454AbiI1SMW (ORCPT ); Wed, 28 Sep 2022 14:12:22 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 52C7CD0789 for ; Wed, 28 Sep 2022 11:12:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1664388738; 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=cNfUBfM5k+VGHxWCr84qkrW95eGzYmSzPp620mykmfE=; b=ALX/68YhLPitEQB/zpBri8ADjKNOBltFLLWuBFZkmtt8q87VUXR2QlJbYIlq56f6syORPn TyJPTt+4mUWSI48r/mNNv+kUOlbfr5vw/whkqZG8j6rgYY8xajstbP4EIcDt16pUcW+SFL PRfDBJw5taxUJwUpw9i0F0C/bGrehs0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.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-316-9_Ze1mxeM3aczndKUOw7jw-1; Wed, 28 Sep 2022 14:12:15 -0400 X-MC-Unique: 9_Ze1mxeM3aczndKUOw7jw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8029E1C06EC9; Wed, 28 Sep 2022 18:11:59 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.68]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E31D12027061; Wed, 28 Sep 2022 18:11:55 +0000 (UTC) Date: Wed, 28 Sep 2022 19:11:53 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Pierre Morel Cc: qemu-s390x@nongnu.org, qemu-devel@nongnu.org, borntraeger@de.ibm.com, pasic@linux.ibm.com, richard.henderson@linaro.org, david@redhat.com, thuth@redhat.com, cohuck@redhat.com, mst@redhat.com, pbonzini@redhat.com, kvm@vger.kernel.org, ehabkost@redhat.com, marcel.apfelbaum@gmail.com, eblake@redhat.com, armbru@redhat.com, seiden@linux.ibm.com, nrb@linux.ibm.com, frankja@linux.ibm.com Subject: Re: [PATCH v9 01/10] s390x/cpus: Make absence of multithreading clear Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20220902075531.188916-1-pmorel@linux.ibm.com> <20220902075531.188916-2-pmorel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220902075531.188916-2-pmorel@linux.ibm.com> User-Agent: Mutt/2.2.6 (2022-06-05) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Sep 02, 2022 at 09:55:22AM +0200, Pierre Morel wrote: > S390x do not support multithreading in the guest. > Do not let admin falsely specify multithreading on QEMU > smp commandline. > > Signed-off-by: Pierre Morel > --- > hw/s390x/s390-virtio-ccw.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c > index 70229b102b..b5ca154e2f 100644 > --- a/hw/s390x/s390-virtio-ccw.c > +++ b/hw/s390x/s390-virtio-ccw.c > @@ -86,6 +86,9 @@ static void s390_init_cpus(MachineState *machine) > MachineClass *mc = MACHINE_GET_CLASS(machine); > int i; > > + /* Explicitely do not support threads */ > + assert(machine->smp.threads == 1); What is the functional effect for currently released QEMU versions if a user has set threads == 2 for an s390 machine ? Is the threads setting simply ignored ? If we want to eliminate this mistake, then there's two possible options * If it had no effect, treat this like a deprecation process where we print a warning for 2 releases, and then turn the warning into an error. Gives a little grace to fix the config mistakes some users might have made, at a time convenient to them. Or * If it had effect and we need migration compatibility then forbid threads > 1 only for new machine type versions, so existing deployed guests are not changed. 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 :|