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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 9B718C433ED for ; Sat, 10 Apr 2021 04:54:05 +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 D5B8F6113A for ; Sat, 10 Apr 2021 04:54:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D5B8F6113A 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]:36358 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lV5dD-0002oO-RK for qemu-devel@archiver.kernel.org; Sat, 10 Apr 2021 00:54:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59726) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lV5cf-0002Pg-8p for qemu-devel@nongnu.org; Sat, 10 Apr 2021 00:53:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58756) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lV5cd-0004Un-8h for qemu-devel@nongnu.org; Sat, 10 Apr 2021 00:53:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618030406; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JXvsnzl5elCW3wpiWMP26qqX9QPSXaBSTlbD2NcboFQ=; b=Bq1wNCfj0BNOH4wpcuFhYr0p43vIzX2sCKd0zuWqCtuaRlEmBVxCtfJfy8SJNBOZA8oDDe m/RgrZmHMvMgtLrYVxKPhNj+D0KZIm7R67RxY951e4+5Ty3tGAe3HECESL7rVhfoAr2Zf0 PVsMcfcQbNsm/rCmixq6quLV+JuD9mM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-329-qyMUW30bMjOjzdbQMtI7aQ-1; Sat, 10 Apr 2021 00:53:24 -0400 X-MC-Unique: qyMUW30bMjOjzdbQMtI7aQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 031D9802B5B; Sat, 10 Apr 2021 04:53:23 +0000 (UTC) Received: from thuth.remote.csb (ovpn-112-20.ams2.redhat.com [10.36.112.20]) by smtp.corp.redhat.com (Postfix) with ESMTP id 123ED5B4BF; Sat, 10 Apr 2021 04:53:20 +0000 (UTC) To: Greg Kurz , qemu-devel@nongnu.org References: <20210409160339.500167-1-groug@kaod.org> <20210409160339.500167-3-groug@kaod.org> From: Thomas Huth Subject: Re: [PATCH 2/2] cpu/core: Fix "help" of CPU core device types Message-ID: Date: Sat, 10 Apr 2021 06:53:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210409160339.500167-3-groug@kaod.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Eduardo Habkost , Markus Armbruster , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 09/04/2021 18.03, Greg Kurz wrote: > Calling qdev_get_machine() from a QOM instance_init function is > fragile because we can't be sure the machine object actually > exists. And this happens to break when passing ",help" on the > command line to get the list of properties for a CPU core > device types : > > $ ./qemu-system-ppc64 -device power8_v2.0-spapr-cpu-core,help > qemu-system-ppc64: ../../hw/core/machine.c:1290: > qdev_get_machine: Assertion `machine != NULL' failed. > Aborted (core dumped) > > This used to work before QEMU 5.0, but commit 3df261b6676b > unwillingly introduced a subtle regression : the above command > line needs to create an instance but the instance_init function > of the base class calls qdev_get_machine() before > qemu_create_machine() has been called, which is a programming bug. > > Use current_machine instead. It is okay to skip the setting of > nr_thread in this case since only its type is displayed. > > Reported-by: Thomas Huth > Fixes: 3df261b6676b ("softmmu/vl.c: Handle '-cpu help' and '-device help' before 'no default machine'") > Cc: peter.maydell@linaro.org > Signed-off-by: Greg Kurz > --- > hw/cpu/core.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/hw/cpu/core.c b/hw/cpu/core.c > index 92d3b2fbad62..987607515574 100644 > --- a/hw/cpu/core.c > +++ b/hw/cpu/core.c > @@ -66,10 +66,16 @@ static void core_prop_set_nr_threads(Object *obj, Visitor *v, const char *name, > > static void cpu_core_instance_init(Object *obj) > { > - MachineState *ms = MACHINE(qdev_get_machine()); > CPUCore *core = CPU_CORE(obj); > > - core->nr_threads = ms->smp.threads; > + /* > + * Only '-device something-cpu-core,help' can get us there before > + * the machine has been created. We don't care to set nr_threads > + * in this case since it isn't used afterwards. > + */ > + if (current_machine) { > + core->nr_threads = current_machine->smp.threads; > + } > } Ack for QEMU 6.0 to get rid of the crash. But note that using current_machine might also be wrong in some cases. It's e.g. possible that the user started QEMU with a different machine type (e.g. -M g3beige) and then uses some QOM commands to introspect the available devices - in that case, this instance_init function will be executed with current_machine pointing to a G3 Mac - which is certainly also not what we want here. It likely does not crash, but still ... using current_machine or qdev_get_machine() in an instance_init() function is just wrong. This nr_thread stuff should likely be done in the realize function instead. Thomas