From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [PATCH 08/18] PVH xen: tools changes to create PVH domain Date: Fri, 30 Aug 2013 11:22:36 +0100 Message-ID: <5220726C.1060202@eu.citrix.com> References: <1369445137-19755-1-git-send-email-mukesh.rathor@oracle.com> <1369445137-19755-9-git-send-email-mukesh.rathor@oracle.com> <1371049088.24512.450.camel@zakaz.uk.xensource.com> <20130614171437.49f55cea@mantra.us.oracle.com> <1371467494.23802.49.camel@zakaz.uk.xensource.com> <20130730164716.10969419@mantra.us.oracle.com> <1375272057.7382.24.camel@kazak.uk.xensource.com> <20130731190213.0b57efd0@mantra.us.oracle.com> <1377775784.11455.23.camel@kazak.uk.xensource.com> <20130829182425.20b56e2d@mantra.us.oracle.com> <1377856404.11455.62.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1377856404.11455.62.camel@kazak.uk.xensource.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: Ian Campbell Cc: "Xen-devel@lists.xensource.com" , Ian Jackson List-Id: xen-devel@lists.xenproject.org On 30/08/13 10:53, Ian Campbell wrote: > On Thu, 2013-08-29 at 18:24 -0700, Mukesh Rathor wrote: >> On Thu, 29 Aug 2013 12:29:44 +0100 >> Ian Campbell wrote: >> >>> On Thu, 2013-08-29 at 12:13 +0100, George Dunlap wrote: >>>> On Thu, Aug 1, 2013 at 3:02 AM, Mukesh Rathor >>>> wrote: >>>>>> I'm not sure how you are currently signalling to the hypervisor >>>>>> that a new domain is a PVH domain? I had a look through this >>>>>> patch and must be being thick because I don't see it. >>>>> I had a flag set, but it was recommended during RFC to remove it. >>>>> So, now in xen, a PV with HAP is a PVH guest: >>>> Why was it recommended to remove it? >>>> >>>> "PVH == PV + HAP" is a ridiculous interface, and one which will make >>>> it hard to import shadow in the future. In my series I'm planning >>>> on adding XEN_DOMCTL_CDF_pvh_guest, and using that instead. >>> These are not stable ABI interfaces, so if someone wants to do PVH >>> with Shadow then they can just change it. >> I thought we named PVH for PV with HAP :) > I thought it was H for HVM myself ;-) We always talked about an "HVM container", in part to gain back the extra protection levels lost when they took away the segmentation limits for x86-64. From a Linux maintenance perspective, autotranslate is of course a big win; but there's no reason in principle that we couldn't have used shadow pagetables for that. HAP is a big win in some cases, but a loss in others; it is not, as far as I'm concerned, the primary reason for introducing this mode. -George