From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH] x86: add feature flags to shared_info page Date: Mon, 2 Mar 2015 13:50:54 +0000 Message-ID: <1425304254.21151.28.camel@citrix.com> References: <1425301144-27119-1-git-send-email-jgross@suse.com> <54F470740200007800065076@mail.emea.novell.com> <54F4694D.3010808@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YSQkP-0007BK-4w for xen-devel@lists.xenproject.org; Mon, 02 Mar 2015 13:51:01 +0000 In-Reply-To: <54F4694D.3010808@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: Andrew Cooper Cc: Juergen Gross , keir@xen.org, tim@xen.org, ian.jackson@eu.citrix.com, david.vrabel@citrix.com, Jan Beulich , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On Mon, 2015-03-02 at 13:44 +0000, Andrew Cooper wrote: > On 02/03/15 13:15, Jan Beulich wrote: > >>>> On 02.03.15 at 13:59, <"jgross@suse.com".non-mime.internet> wrote: > >> In order to indicate the Xen tools capability to support the virtual > >> mapped linear p2m list instead the 3 level mfn tree add feature flags > >> to the shared_info page. > > But why in the shared info page? They'd belong to start info or should > > be obtainable via XENVER_get_features. > > Furthermore in this case, the virtual linear p2m is purely a > guest->toolstack feature/ABI. > > Xen deliberately has no knowledge of PV guest p2ms of either the 3level > or linear variety. > > Is there genuinely no better interface than the hypervisor feature flags > to indicate a piece of toolstack support? Per docs/misc/xenstore-paths.markdown there are platform-feature flags in ~/control/ (multiproc suspend and xs_reset support) but that might be available to the guest too late for this use case? Ian.