From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: PCI Passthrough Design - Draft 3
Date: Wed, 12 Aug 2015 10:25:49 -0400
Message-ID: <20150812142549.GE17002@l.oracle.com>
References: <55C0AFAC.9070706@caviumnetworks.com>
	<20150811203445.GE7765@l.oracle.com>
	<1439369801.9747.314.camel@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Content-Disposition: inline
In-Reply-To: <1439369801.9747.314.camel@citrix.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Ian Campbell <ian.campbell@citrix.com>
Cc: "Prasun.kapoor@cavium.com" <Prasun.kapoor@cavium.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Manish Jaggi <mjaggi@caviumnetworks.com>, "Kumar,
	Vijaya" <Vijaya.Kumar@caviumnetworks.com>, Julien Grall <julien.grall@linaro.org>, Xen Devel <xen-devel@lists.xen.org>
List-Id: xen-devel@lists.xenproject.org

On Wed, Aug 12, 2015 at 09:56:41AM +0100, Ian Campbell wrote:
> On Tue, 2015-08-11 at 16:34 -0400, Konrad Rzeszutek Wilk wrote:
> > 
> > > 2.2    PHYSDEVOP_pci_host_bridge_add hypercall
> > > ----------------------------------------------
> > > Xen code accesses PCI configuration space based on the sbdf received from
> > > the
> > > guest. The order in which the pci device tree node appear may not be the
> > > same
> > > order of device enumeration in dom0. Thus there needs to be a mechanism to
> > > bind
> > > the segment number assigned by dom0 to the pci host controller. The
> > > hypercall
> > > is introduced:
> > 
> > Why can't we extend the existing hypercall to have the segment value?
> > 
> > Oh wait, PHYSDEVOP_manage_pci_add_ext does it already!
> > 
> > And have the hypercall (and Xen) be able to deal with introduction of PCI
> > devices that are out of sync?
> > 
> > Maybe I am confused but aren't PCI host controllers also 'uploaded' to
> > Xen?
> 
> The issue is that Dom0 and Xen need to agree on a common numbering space
> for the "PCI domain" AKA "segment", which is really just a software concept
> i.e. on ARM Linux just makes them up (on x86 I believe they come from some
> firmware table so Xen and Dom0 "agree" to both use that).

Doesn't the PCI domain or segments have an notion of which PCI devices are
underneath it? Or vice-verse - PCI devices know what their segment (or domain) is?

> 
> Ian.
>