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 22C43CAC5A7 for ; Tue, 23 Sep 2025 15:25:23 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v14sz-0005A6-Mg; Tue, 23 Sep 2025 11:24:57 -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 1v14sp-00058x-E2 for qemu-devel@nongnu.org; Tue, 23 Sep 2025 11:24:48 -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 1v14sm-0002KG-V4 for qemu-devel@nongnu.org; Tue, 23 Sep 2025 11:24:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758641082; 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=GLyrTcqqNuaEFEFXx9yMKuhx535TvJEYGetYtD/el3E=; b=fu6LzHk/5oiP60uvfA5rFbFlTX8j7Cy9VgQFmumOTjzsJDwYRhpRVcFKNL1SyNweTLj8io IUbf3ihSgzcscOM58Bw/aE4F2sdxusEYgNmC8oMWDfTy6bKwxCGLllL3wyb//QJtYGGR/d EVS6rUtR/ndMR5lUTS+VSi0gq0h135U= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-355-TmdH3AufPCa6olN31-22GQ-1; Tue, 23 Sep 2025 11:24:40 -0400 X-MC-Unique: TmdH3AufPCa6olN31-22GQ-1 X-Mimecast-MFC-AGG-ID: TmdH3AufPCa6olN31-22GQ_1758641080 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DC59318002C8 for ; Tue, 23 Sep 2025 15:24:39 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.53]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E5A4819560BB; Tue, 23 Sep 2025 15:24:37 +0000 (UTC) Date: Tue, 23 Sep 2025 16:24:34 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Igor Mammedov Cc: qemu-devel@nongnu.org, mst@redhat.com, Gerd Hoffmann Subject: Re: [PATCH] x86: ich9: fix default value of 'No Reboot' bit in GCS Message-ID: References: <20250922132600.562193-1-imammedo@redhat.com> <20250923104051.1b71d6ea@fedora> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250923104051.1b71d6ea@fedora> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.442, 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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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 Tue, Sep 23, 2025 at 10:40:51AM +0200, Igor Mammedov wrote: > On Mon, 22 Sep 2025 15:24:09 +0100 > Daniel P. Berrangé wrote: > > > On Mon, Sep 22, 2025 at 03:26:00PM +0200, Igor Mammedov wrote: > > > [2] initialized 'No Reboot' bit to 1 by default. And due to quirk it happened > > > to work with linux iTCO_wdt driver (which clears it on module load). > > > > > > However spec [1] states: > > > " > > > R/W. This bit is set when the “No Reboot” strap (SPKR pin on > > > ICH9) is sampled high on PWROK. > > > " > > > > > > So it should be set only when '-global ICH9-LPC.noreboot=true' and cleared > > > when it's false (which should be default). > > > > > > Fix it to behave according to spec and set 'No Reboot' bit only when > > > '-global ICH9-LPC.noreboot=true'. > > > > Is there a real-world problem you hit that is being solved by > > this change, or is it just a theoretical spec compliance fix ? > > I've stumbled upon it when implementing ACPI watchdog POC > > https://gitlab.com/imammedo/qemu/-/commits/wadt_poc > I'm not sure that watchdog table belongs to QEMU, > but the ICH fix definitely is. I've tested this as follows [1] $ make-tiny-image.py --kmod lpc_ich --kmod iTCO_wdt --kmod i2c_i801 $ qemu-system-x86_64 \ -kernel /lib/modules/6.15.9-201.fc42.x86_64/vmlinuz \ -initrd tiny-initrd.img \ -append 'console=ttyS0 quiet' \ -m 1000 \ -display none \ -serial stdio \ -accel kvm \ -M q35 \ -global ICH9-LPC.noreboot=false \ -watchdog-action poweroff \ -trace ich9* -trace tco* ich9_cc_read addr=0x3410 val=0x0 len=4 ich9_cc_write addr=0x3410 val=0x0 len=4 ich9_cc_read addr=0x3410 val=0x0 len=4 tco_io_write addr=0x4 val=0x8 tco_io_write addr=0x6 val=0x2 tco_io_write addr=0x6 val=0x4 tco_io_read addr=0x8 val=0x0 tco_io_read addr=0x12 val=0x4 tco_io_write addr=0x12 val=0x32 tco_io_read addr=0x12 val=0x32 tco_io_write addr=0x0 val=0x1 tco_timer_reload ticks=50 (30000 ms) ~ # mknod /dev/watchdog0 c 10 130 ~ # cat /dev/watchdog0 tco_io_write addr=0x0 val=0x1 tco_timer_reload ticks=50 (30000 ms) cat: read error: Invalid argument [ 5.646147] watchdog: watchdog0: watchdog did not stop! tco_io_write addr=0x0 val=0x1 tco_timer_reload ticks=50 (30000 ms) ~ # tco_timer_expired timeouts_no=0 no_reboot=0/0 tco_timer_reload ticks=50 (30000 ms) tco_timer_expired timeouts_no=1 no_reboot=0/0 And the same, but with ICH9-LPC.noreboot=true. I see no functional change from Linux guest POV in either scenario before/after this patch, so Tested-by: Daniel P. Berrangé Reviewed-by: Daniel P. Berrangé With regards, Daniel [1] https://gitlab.com/berrange/tiny-vm-tools/-/blob/master/make-tiny-image.py -- |: 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 :|