From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161308AbcFHP5p (ORCPT ); Wed, 8 Jun 2016 11:57:45 -0400 Received: from mail-wm0-f52.google.com ([74.125.82.52]:36306 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754682AbcFHP5n convert rfc822-to-8bit (ORCPT ); Wed, 8 Jun 2016 11:57:43 -0400 Subject: Re: Using DT overlays for adding virtual hardware Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Content-Type: text/plain; charset=utf-8 From: Pantelis Antoniou In-Reply-To: <20160608151745.GB13355@leverpostej> Date: Wed, 8 Jun 2016 18:57:37 +0300 Cc: Jan Kiszka , devicetree , Linux Kernel Mailing List , Jailhouse , =?utf-8?Q?M=C3=A5ns_Rullg=C3=A5rd?= , Antonios Motakis Content-Transfer-Encoding: 8BIT Message-Id: <28BC1AEC-6A7D-4A97-82F4-5670E884C41D@konsulko.com> References: <575828C0.5000008@siemens.com> <20160608151745.GB13355@leverpostej> To: Mark Rutland X-Mailer: Apple Mail (2.3124) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mark, > On Jun 8, 2016, at 18:17 , 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. > As far as I understand it PCI is just one of the cases. You could conceivably inject any kind of virtio device like serial/storage networking etc. The question is since overlays exist and do work, why should he do anything else besides using them? I doubt he’s interested in writing yet another driver for something that already exists and works. > Thanks, > Mark. Regards — Pantelis