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 04E28C433EF for ; Wed, 20 Jul 2022 11:02:09 +0000 (UTC) Received: from localhost ([::1]:45336 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oE7Sy-0004hF-T4 for qemu-devel@archiver.kernel.org; Wed, 20 Jul 2022 07:02:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55080) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oE7RP-0003vF-Ak for qemu-devel@nongnu.org; Wed, 20 Jul 2022 07:00:31 -0400 Received: from forwardcorp1o.mail.yandex.net ([2a02:6b8:0:1a2d::193]:47910) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oE7RL-00051o-Du for qemu-devel@nongnu.org; Wed, 20 Jul 2022 07:00:30 -0400 Received: from sas1-c73b4b4f4b95.qloud-c.yandex.net (sas1-c73b4b4f4b95.qloud-c.yandex.net [IPv6:2a02:6b8:c08:12a9:0:640:c73b:4b4f]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id 2D4E62E0E7D; Wed, 20 Jul 2022 14:00:19 +0300 (MSK) Received: from rvkaganb (unknown [2a02:6b8:0:419:7359:4dc3:71d:4c5a]) by sas1-c73b4b4f4b95.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id wpMt44tDjY-0HOqPnGh; Wed, 20 Jul 2022 11:00:18 +0000 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client certificate not present) Precedence: bulk X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1658314818; bh=XpmszliWJ7NkCnisG0QAFiXK30JqkpU2JJcQIKKtPHI=; h=In-Reply-To:Cc:Message-ID:Subject:Date:References:To:From; b=kawogI+JbtaXmsN8VhRLGuhk9vhTitJcQc5naXrfYJiov7KubcYBqFqYlyUxIQfGl xFvkjlQ6pTTfEpStvERnw7gbY/Ww0oH75JpdD3b6DM+DEPUzUupRMXx3nvQxMPwPI4 jvkUcLY9JkW7A2KW/pKMwEXzVBzBrsmDZm0WuFo4= Authentication-Results: sas1-c73b4b4f4b95.qloud-c.yandex.net; dkim=pass header.i=@yandex-team.ru Date: Wed, 20 Jul 2022 14:00:16 +0300 From: Roman Kagan To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Cc: qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy , Thomas Huth , Laurent Vivier , Marcel Apfelbaum , yc-core@yandex-team.ru, Paolo Bonzini , "Michael S. Tsirkin" Subject: Re: [PATCH v3] hw/pci/pci_bridge: ensure PCIe slots have only one slot Message-ID: Mail-Followup-To: Roman Kagan , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy , Thomas Huth , Laurent Vivier , Marcel Apfelbaum , yc-core@yandex-team.ru, Paolo Bonzini , "Michael S. Tsirkin" References: <20220720102555.874394-1-rvkagan@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=2a02:6b8:0:1a2d::193; envelope-from=rvkagan@yandex-team.ru; helo=forwardcorp1o.mail.yandex.net X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Jul 20, 2022 at 11:44:26AM +0100, Daniel P. Berrangé wrote: > On Wed, Jul 20, 2022 at 01:25:55PM +0300, Roman Kagan wrote: > > It's possible to create non-working configurations by attaching a device > > to a derivative of PCIe slot (pcie-root-port, ioh3420, etc) and > > specifying a slot number other that zero, e.g.: > > > > -device pcie-root-port,id=s0,... \ > > -device virtio-blk-pci,bus=s0,addr=4,... > > > > Make QEMU reject such configurations and only allow addr=0 on the > > secondary bus of a PCIe slot. > > What do you mean by 'non-working' in this case. The guest OS boots > OK, but I indeed don't see the device in the guest, but IIUC it was > said that was just because Linux doesn't scan for a non-zero slot. Right. I don't remember if it was Linux or firmware or both but indeed at least Linux guests don't see devices if attached to a PCIe slot at addr != 0. (Which is kinda natural for a thing called "slot", isn't it?) > That wouldn't be a broken config from QEMU's POV though, merely a > guest OS limitation ? Strictly speaking it wouldn't, indeed. But we've had created such a configuration (due to a bug in our management layer) and spent non-negligible time trying to figure out why the attached device didn't appear in the guest. So I thought it made sense to reject a configuration which is known to confuse guests. Doesn't it? Thanks, Roman.