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 E9BB4ECAAA1 for ; Tue, 1 Nov 2022 13:32:20 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1opqvV-00060m-Iw; Tue, 01 Nov 2022 09:03:33 -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 1opqvQ-00060X-PG for qemu-devel@nongnu.org; Tue, 01 Nov 2022 09:03:31 -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 1opqvN-0004gt-Q9 for qemu-devel@nongnu.org; Tue, 01 Nov 2022 09:03:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667307804; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PfbsZR015ivW22b0T312uPqQ2KeuvQNa6ybcWQAGwdU=; b=dulZmWD54ZoRLC9FoATpRyv3xTjgwaiA516EUNxfQkzDFsNvaYB2TEXza8b3TyY70Ofntl ElFBYLm8i7O8IKq61rNAASUwg5mAlIy1tgfl419YruMz9C1c/W7wvGTK0R9qAzJERP1W5m MWHPwGaZAF9M+XfaYy0247B20Raw+Dw= 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-101-q87dGpMPPLutmjk77SYMfA-1; Tue, 01 Nov 2022 09:03:22 -0400 X-MC-Unique: q87dGpMPPLutmjk77SYMfA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 16E8529DD9AD; Tue, 1 Nov 2022 13:03:22 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.145]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1D15C111DCE7; Tue, 1 Nov 2022 13:03:19 +0000 (UTC) Date: Tue, 1 Nov 2022 13:03:17 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Igor Mammedov Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Laurent Vivier , Richard Henderson , Ani Sinha , Thomas Huth , Paolo Bonzini , Eduardo Habkost , Marcel Apfelbaum , "Richard W.M. Jones" Subject: Re: [PATCH 0/4] hw: make TCO watchdog actually work by default for Q35 Message-ID: References: <20221031131934.425448-1-berrange@redhat.com> <20221031114835-mutt-send-email-mst@kernel.org> <20221101135724.7f89868c@fedora> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221101135724.7f89868c@fedora> User-Agent: Mutt/2.2.7 (2022-08-07) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 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: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.051, 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_H2=-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?= Sender: "Qemu-devel" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Nov 01, 2022 at 01:57:24PM +0100, Igor Mammedov wrote: > On Mon, 31 Oct 2022 11:48:58 -0400 > "Michael S. Tsirkin" wrote: > > > On Mon, Oct 31, 2022 at 01:50:24PM +0000, Daniel P. Berrangé wrote: > > > On Mon, Oct 31, 2022 at 01:19:30PM +0000, Daniel P. Berrangé wrote: > > > > The TCO watchdog is unconditionally integrated into the Q35 machine > > > > type by default, but at the same time is unconditionally disabled > > > > from firing by a host config option that overrides guest OS attempts > > > > to enable it. People have to know to set a magic -global to make > > > > it non-broken > > > > > > Incidentally I found that originally the TCO watchdog was not > > > unconditionally enabled. Its exposure to the guest could be > > > turned on/off using > > > > > > -global ICH9-LPC.enable_tco=bool > > > > > > This was implemented for machine type compat, but it also gave > > > apps a way to disable the watchdog functionality. Unfortunately > > > that ability was discarded in this series: > > > > > > https://lore.kernel.org/all/1453564933-29638-1-git-send-email-ehabkost@redhat.com/ > > > > > > but the 'enable_tco' property still exists in QOM, but silently > > > ignored. > > > > > > Seems we should either fix the impl of 'enable_tco', or remove the > > > QOM property entirely, so we don't pretend it can be toggled anymore. > > > > > > With regards, > > > Daniel > > > > i am inclined to say you are right and the fix is to fix the impl. > > Is there need for users to disable whatchdog at all? > It was always present since then and no one complained, > so perhaps we should ditch property instead fixing it > to keep it simple. Thinking about it more, I think we should NOT fix the 'enable_tco' property, because there will be no way for a mgmt appp to tell if they're using a fixed or broken QEMU. So if they use 'enable_tco' on a broken QEMU and then live migrate, they'll get an guest ABI change. If we did want to support disabling it, then we should have a brand new property that apps can probe for. In the absence of a request to disable watchdog, I'd say we just delete 'enable_tco' right now. If someone wants it in future, we can add it with a new name. 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 :|