From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCHv1] xen/balloon: disable memory hotplug in PV guests Date: Tue, 10 Mar 2015 09:35:04 -0400 Message-ID: <54FEF308.3090702@oracle.com> References: <1425910200-17541-1-git-send-email-david.vrabel@citrix.com> <54FED833.1080609@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YVKKr-0002Ej-30 for xen-devel@lists.xenproject.org; Tue, 10 Mar 2015 13:36:37 +0000 In-Reply-To: <54FED833.1080609@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: David Vrabel , xen-devel@lists.xenproject.org Cc: Daniel Kiper List-Id: xen-devel@lists.xenproject.org On 03/10/2015 07:40 AM, David Vrabel wrote: > On 09/03/15 14:10, David Vrabel wrote: >> Memory hotplug doesn't work with PV guests because: >> >> a) The p2m cannot be expanded to cover the new sections. > Broken by 054954eb051f35e74b75a566a96fe756015352c8 (xen: switch to > linear virtual mapped sparse p2m list). > > This one would be non-trivial to fix. We'd need a sparse set of > vm_area's for the p2m or similar. > >> b) add_memory() builds page tables for the new sections which means >> the new pages must have valid p2m entries (or a BUG occurs). > After some more testing this appears to be broken by: > > 25b884a83d487fd62c3de7ac1ab5549979188482 (x86/xen: set regions above the > end of RAM as 1:1) included 3.16. > > This one can be trivially fixed by setting the new sections in the p2m > to INVALID_P2M_ENTRY before calling add_memory(). Have you tried 3.17? As I said yesterday, it worked for me (with 4.4 Xen). -boris