From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: PVHVM drivers in upstream linux kernel
Date: Tue, 02 Dec 2014 15:35:28 +0100
Message-ID: <547DCE30.4080303@suse.com>
References: <547D88EF.4050206@suse.com> <547D9A4A.6010201@citrix.com>
	<1417518314.24320.9.camel@citrix.com> <547DA392.90701@suse.com>
	<547DA99E.5080001@citrix.com> <547DB802.9020900@suse.com>
	<547DC80A.10301@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <547DC80A.10301@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: David Vrabel <david.vrabel@citrix.com>, Ian Campbell <Ian.Campbell@citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
List-Id: xen-devel@lists.xenproject.org

On 12/02/2014 03:09 PM, David Vrabel wrote:
> On 02/12/14 13:00, Juergen Gross wrote:
>>
>> I'd see:
>> - XEN_PV (selects PARAVIRT, XEN_FRONTEND): be able to run as pv-domain
>>    (x86 only)
>
> Depends on PARAVIRT perhaps?

Chicken and egg problem? :-)

I'd say select, as PARAVIRT isn't a primary function the user wants to
enable, it is a prerequisite for e.g. XEN_PV.

>
>> - XEN_PVHVM (selects XEN_FRONTEND): be able to run as hvm-domain with
>>    pv-drivers
>> - XEN_BACKEND (selects PARAVIRT if x86): be able to run as driver domain
>>    (dom0 or other)
>
> Does not need to select PARAVIRT -- HVM domains can run backends.

Okay.

>
>> - XEN_DOM0 (selects PARAVIRT if x86, XEN_BACKEND): be able to run as
>>    dom0
>
> XEN_DOM0 depends on XEN_PV or XEN_PVH (if x86) and whatever ARM needs.

I've removed XEN_PV as XEN_DOM0 shouldn't require XEN_FRONTEND.
We can add XEN_PARAVIRT instead which will be needed by XEN_DOM0 and
XEN_PV and will select PARAVIRT.

>
>> - XEN_FRONTEND: be able to run as domU with pv-drivers
>
> It may also be interesting to consider splitting the PV MMU stuff under
> a PARAVIRT_MMU option.  This might address a reason why people want to
> disable PARAVIRT completely.

Okay, seems sensible. Especially regarding XEN_PVH which I've omitted
here.

I'll try to assemble a complete config tree for review before starting
with patches. :-)


Juergen