From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCHv1] xen/balloon: disable memory hotplug in PV guests Date: Tue, 10 Mar 2015 11:40:35 +0000 Message-ID: <54FED833.1080609@citrix.com> References: <1425910200-17541-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YVIWy-0002kJ-5a for xen-devel@lists.xenproject.org; Tue, 10 Mar 2015 11:41:00 +0000 In-Reply-To: <1425910200-17541-1-git-send-email-david.vrabel@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: xen-devel@lists.xenproject.org Cc: Boris Ostrovsky , Daniel Kiper List-Id: xen-devel@lists.xenproject.org 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(). David