From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH] x86: Expose hypervisor's PVH support via xen_caps Date: Fri, 23 May 2014 11:53:38 -0400 Message-ID: <537F6F02.7060704@oracle.com> References: <1400856933-1424-1-git-send-email-boris.ostrovsky@oracle.com> <537F6287.5070705@citrix.com> <537F6471.40000@oracle.com> <537F675B.8080603@citrix.com> <537F69F5.7060309@oracle.com> <537F6AA4.9020501@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <537F6AA4.9020501@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= Cc: Andrew Cooper , keir@xen.org, Tim Deegan , jbeulich@suse.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 05/23/2014 11:35 AM, Roger Pau Monn=E9 wrote: > On 23/05/14 17:32, Boris Ostrovsky wrote: >> On 05/23/2014 11:20 AM, Andrew Cooper wrote: >>> On 23/05/14 16:08, Boris Ostrovsky wrote: >>>> On 05/23/2014 11:00 AM, Andrew Cooper wrote: >>>>> On 23/05/14 15:55, Boris Ostrovsky wrote: >>>>>> Signed-off-by: Boris Ostrovsky >>>>>> --- >>>>>> xen/arch/x86/setup.c | 5 +++++ >>>>>> 1 file changed, 5 insertions(+) >>>>> If the plan is to try and PVH and HVM back into one mode as far as Xen >>>>> is concerned, doesn't this become redundant? >>>> Yes, I was thinking about this but we currently don't have (or, >>>> rather, I can't think of) a good way to determine whether we can start >>>> a PVH guest. We can grep the log but that doesn't feel like a >>>> particularly good solution. >>>> >>>> One option could be to postpone this patch until 4.5 freezes and see >>>> whether we indeed followed up on the plan and if we didn't then >>>> integrate it. >>>> >>>> -boris >>> My concern here is that if this patch gets accepted, it will have to say >>> forever more as the cap strings are a very public API. >> Yes, that's true. >> >> The problem that we have now is that if we have 'pvh=3D1' in the config >> file the guest will fail to start if PVH is not on. Can we, for example, >> revert (with a warning) to pure PV if that's the case? > Won't this option go away once PVH is stable, so the toolstack can > detect if the kernel supports PVH and start the guest in this mode by > default? (of course falling back to PV if PVH is not supported). Yes, it will, by virtue of hypervisor never having to take this action = (reverting to PV) since PVH would be stable and always supported. I just don't know whether ignoring pvh=3D1 directive on systems where PVH = is not supported is acceptable. (Your "of course" seems to indicate that = you think it is.) -boris