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 2B86FE9A74D for ; Tue, 24 Mar 2026 10:00:18 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w4yXv-0004zw-1j; Tue, 24 Mar 2026 05:59:35 -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 1w4yXt-0004zV-Bu for qemu-devel@nongnu.org; Tue, 24 Mar 2026 05:59:33 -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 1w4yXr-0002cf-4R for qemu-devel@nongnu.org; Tue, 24 Mar 2026 05:59:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774346369; 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=TJ1vMBEe8Dsw41A89pk6yrT2C5ogE9dQJMhAO/T+c5w=; b=SqTICbrYwereK8+NrlWc0G7dWUNQbYApvjchxqTfOSsiezUhtalY4pD+idoctvOC4xXr19 DsKI4OPxwL/rhg0zEuA3ZDhjlBCQvMpCfdEP5hxbR5FRbDziRLlflxASKOtE4HhBJ+IrA+ 44k5Dfz296QuIwGSRVo7qZx/kwe5wPk= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-341-7uC1TSxwOT6Xs_9QeCDb0A-1; Tue, 24 Mar 2026 05:59:23 -0400 X-MC-Unique: 7uC1TSxwOT6Xs_9QeCDb0A-1 X-Mimecast-MFC-AGG-ID: 7uC1TSxwOT6Xs_9QeCDb0A_1774346362 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3313119560AA; Tue, 24 Mar 2026 09:59:22 +0000 (UTC) Received: from redhat.com (unknown [10.44.33.93]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 26D43180058B; Tue, 24 Mar 2026 09:59:17 +0000 (UTC) Date: Tue, 24 Mar 2026 09:59:14 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Anthony PERARD Cc: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= , Thierry Escande , qemu-devel@nongnu.org, Paolo Bonzini , Richard Henderson , "Michael S. Tsirkin" , Eduardo Habkost , xen-devel@lists.xenproject.org Subject: Re: [PATCH 0/4] Xen: Add Q35 initial support for HVM guests Message-ID: References: <20260313164649.794591-1-thierry.escande@vates.tech> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=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: qemu development 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, Mar 24, 2026 at 09:28:00AM +0000, Anthony PERARD wrote: > On Sat, Mar 14, 2026 at 03:16:15PM +0100, Marek Marczykowski-Górecki wrote: > > On Fri, Mar 13, 2026 at 04:46:56PM +0000, Thierry Escande wrote: > > > This patch series introduces Q35 chipset support for Xen HVM guests. This is > > > based on the work from Alexey Gerasimenko (See patchset [1] for reference). > > > > > > This series does not implement device passthrough as this will need more work > > > on the Xen side to support multiple PCI buses. Since Q35 chipset does not > > > support device hotplugging and with current Xen mechanism for device > > > passthrough, they have to be plugged to a new PCIe root port, i.e. not the PCI > > > bus 0. > > > > I always found it weird that Xen does hot-plugging of PCI passthrough > > devices... Wouldn't it be easier to change this (connect them from the > > very start, via QEMU cmdline) and declare hotplug as unsupported (at > > least at this time)? I realize it's more complex change at the toolstack > > side, but overall may simplify things and maybe even improve > > reliability. > > Skipping hot-plug on Q35 sounds good to me. > > I though we could keep using QMP to do cold plug, with the experimental > "--preconfig", but "device_add" isn't allowed :-(. So yes, doing this > via command line sounds fine. > > In libxl, we might be able to transform the json for `device_add` into > the command line counterpart for `-device` fairly easily so the argument > are only generated in a single place. Then we could skip the QMP > "device_add" in libxl when it's already done via command line. -device accepts JSON directly, so there's no transformation you need to do from the QMP JSON. For example: -device '{"driver":"pcie-root-port","port":8,"chassis":1,"id":"pci.1","bus":"pcie.0","multifunction":true,"addr":"0x1"}' Likewise -object, -audiodev and -netdev accept QMP JSON too With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|