From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757514AbcFHP1l (ORCPT ); Wed, 8 Jun 2016 11:27:41 -0400 Received: from thoth.sbs.de ([192.35.17.2]:56977 "EHLO thoth.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757498AbcFHP1j (ORCPT ); Wed, 8 Jun 2016 11:27:39 -0400 Subject: Re: Using DT overlays for adding virtual hardware To: Mark Rutland References: <575828C0.5000008@siemens.com> <20160608151745.GB13355@leverpostej> Cc: devicetree , Pantelis Antoniou , Linux Kernel Mailing List , Jailhouse , =?UTF-8?B?TcOlbnMgUnVsbGfDpXJk?= , Antonios Motakis From: Jan Kiszka Message-ID: <5758395E.4000508@siemens.com> Date: Wed, 8 Jun 2016 17:27:26 +0200 User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 In-Reply-To: <20160608151745.GB13355@leverpostej> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016-06-08 17:17, Mark Rutland wrote: > On Wed, Jun 08, 2016 at 04:16:32PM +0200, Jan Kiszka wrote: >> Hi all, >> >> already started the discussion off-list with Pantelis, but it's better >> done in public: >> >> I'm currently exploring ways to make Linux recognize dynamically added >> virtual hardware when running under the Jailhouse hypervisor [1]. We >> need to load drivers for inter-partition communication devices that only >> appear after Jailhouse started (which is done from within Linux, i.e. >> long after boot) or when a partition was added later on. Probably, we >> will simply add a virtual PCI host bridge on systems without physical >> PCI and let the IPC device be explored that way (already works on x86). >> Still, that leaves us with hotplug and unplug on hypervisor activation >> and deactivation. > > If I've understood correctly you want to use overlays to inject the > virtual PCI host bridge? > > Given that you know precisely what you want to inject, I'm not sure I > see the value of using an overlay. > > Is there some reason you can't just create a device without having to go > via an intermediate step? As I understand it, Xen does that for (some) > virtual devices provided to Dom0 and DomU. I don't want to write yet another virtual driver but ideally reuse pci-host-generic. Possibly a dumb question, but bow can I make Linux instantiate a device node compatible with that driver and with the desired resources? That's what made me think of overlays. Thanks, Jan -- Siemens AG, Corporate Technology, CT RDA ITP SES-DE Corporate Competence Center Embedded Linux