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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 BC513C433DB for ; Mon, 1 Mar 2021 14:29:21 +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 9319864DA3 for ; Mon, 1 Mar 2021 14:29:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9319864DA3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=proxmox.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57920 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lGjXz-0007R7-OG for qemu-devel@archiver.kernel.org; Mon, 01 Mar 2021 09:29:19 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:42788) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lGjWS-0006Xy-Dt for qemu-devel@nongnu.org; Mon, 01 Mar 2021 09:27:44 -0500 Received: from proxmox-new.maurer-it.com ([212.186.127.180]:50541) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lGjWQ-0006Yh-3g for qemu-devel@nongnu.org; Mon, 01 Mar 2021 09:27:43 -0500 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 25191443CD; Mon, 1 Mar 2021 15:27:39 +0100 (CET) Message-ID: Date: Mon, 1 Mar 2021 15:27:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:87.0) Gecko/20100101 Thunderbird/87.0 Content-Language: en-US To: Igor Mammedov References: <20200730155755.188845-1-mst@redhat.com> <5b40e1ac-03ca-7954-4d50-f5f96c339772@proxmox.com> <20210228154208-mutt-send-email-mst@kernel.org> <967d3e1f-d387-0b33-95b0-6560f49657dd@proxmox.com> <20210301021449-mutt-send-email-mst@kernel.org> <4b7e58a9-e6bf-818f-b2f1-72600fced210@proxmox.com> <20210301152036.0c12cbf5@redhat.com> From: Thomas Lamprecht Subject: Re: [PATCH 1/2] i386/acpi: fix inconsistent QEMU/OVMF device paths In-Reply-To: <20210301152036.0c12cbf5@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=212.186.127.180; envelope-from=t.lamprecht@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, 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: vit9696 , "Michael S. Tsirkin" , Stefan Reiter , qemu-devel@nongnu.org, Paolo Bonzini , Richard Henderson , Laszlo Ersek , Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 01.03.21 15:20, Igor Mammedov wrote: > On Mon, 1 Mar 2021 08:45:53 +0100 > Thomas Lamprecht wrote: >> On 01.03.21 08:20, Michael S. Tsirkin wrote: >>> There are various testing efforts the reason this got undetected is >>> because it does not affect linux guests, and even for windows >>> they kind of recover, there's just some boot slowdown around reconfiguration. >>> Not easy to detect automatically given windows has lots of random >>> downtime during boot around updates etc etc. >>> >> >> No, Windows does not reconfigure, this is a permanent change, one is just lucky >> if one has a DHCP server around in the network accessible for the guest. >> As static addresses setup on that virtual NIC before that config is gone, >> no recovery whatsoever until manual intervention. > Static IP's are the pain guest admin picked up to deal with so he might have to > reconfigure guest OS when it decides to rename NICs. In this case moving > to new QEMU is alike to updating BIOS which fixed PCI description. > (On QEMU side we try to avoid breaking changes, but sometime it happens anyway > and it's up guest admin to fix OS quirks) > heh, I agree, but users see it very differently, QEMU got updated, something stopped working/changed/... -> QEMU at fault. >> I meant more of a "dump HW layout to .txt file, commit to git, and ensure >> there's no diff without and machine version bump" (very boiled down), e.g., like >> ABI checks for kernel builds are often done by distros - albeit those are easier >> as its quite clear what and how the kernel ABI can be used. > ACPI tables are not considered as ABI change in QEMU, technically tables that QEMU > generates are firmware and not version-ed (same like we don't tie anything to > specific firmware versions). > > However we rarely do version ACPI changes (only when it breaks something or > we suspect it would break and we can't accept that breakage), this time it took > a lot of time to find out that. We try to minimize such cases as every > versioning knob adds up to maintenance. > > For ACPI tables changes, QEMU has bios-tables-test, but it lets us to catch > unintended changes only. > Technically it's possible to keep master tables for old machine versions > and test against it. But I'm not sure if we should do that, because some > (most) changes are harmless or useful and should apply to all machine > versions. > So we will end up in the same situation, where we decide if a change > should be versioned or not. > > OK, fair enough. Many thanks for providing some rationale!