This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] [PATCH] dom0 linux: support SBDF with "guestdev=" andrem

To: "Jan Beulich" <jbeulich@xxxxxxxxxx>, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Isaku Yamahata" <yamahata@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] dom0 linux: support SBDF with "guestdev=" andremove "reassigndev="
From: Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>
Date: Fri, 10 Apr 2009 13:46:42 +0900
Delivery-date: Thu, 09 Apr 2009 21:47:16 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <49DDEC91.76E4.0078.0@xxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <20090408172810.EDFC.27C06F64@xxxxxxxxxxxxxxx> <49DDEC91.76E4.0078.0@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
On Thu, 09 Apr 2009 11:39:45 +0100
"Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> >>> Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx> 08.04.09 10:30 >>>
> >This patch supports SBDF with "guestdev=" boot parameter and removes
> >"reassigndev=" boot parameter.
> >
> >Currently there are three boot parameters which specifics PCI device
> >for PCI pass-through.
> >
> >        pciback.hide=
> >        guestdev=
> >        reassigndev=
> >
> >I'd like to simplify them before xen 3.4 is released. To achieve this,
> >I'd like to make "guestdev=" boot parameter support SBDF, and remove
> >"reassigndev=".
> >
> >
> >When we don't need to reassign resources and use device path,
> >pciback.hide= boot parameter can be used. The parameter is also needed
> >for backward compatibility.
> >
> >    pciback.hide=(00:01.0)(00:02.0)
> >
> >When we need to reassign resources or use device path, guestdev= boot
> >parameter can be used. reassign_resources boot parameter is needed to
> >reassign resources, too.
> >
> >    guestdev=00:01.0,00:02.0 reassign_resources
> >    guestdev=PNP0A08:0-1.0,PNP0A08:0-2.0
> >    guestdev=PNP0A08:0-1.0,PNP0A08:0-2.0 reassign_resources
> Which basically means reassignment of resources will become and all-or-
> nothing feature rather than a per-device one - is that really intended? It
> seems like a step backwards to me.

Reassignment of resources is all-or-nothing feature.
When reassign_resources is specified, all PCI devices specified by
"guestdev=" are the targets of reassignment. Please note that PCI
devices which are not specified by "guestdev=" are not the targets of

To avoid fragmentation of resources, all-or-nothing is better than
per-device. On the other hand, if there is a device which cause some
issues on reassignment, per-device is needed. But I have not seen such
a device yet.

Yuji Shimada

Xen-devel mailing list