From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH for-4.5 v6 12/17] xen/arm: Implement domain_get_maximum_gpfn Date: Tue, 16 Sep 2014 17:44:38 +0100 Message-ID: <1410885878.23505.14.camel@citrix.com> References: <1410789775-24197-1-git-send-email-tklengyel@sec.in.tum.de> <1410789775-24197-13-git-send-email-tklengyel@sec.in.tum.de> <1410820740.6908.17.camel@hastur.hellion.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Tamas K Lengyel Cc: Tim Deegan , Julien Grall , Ian Jackson , "xen-devel@lists.xen.org" , Stefano Stabellini , Andres Lagar-Cavilla , Jan Beulich , Daniel De Graaf , Tamas K Lengyel List-Id: xen-devel@lists.xenproject.org On Tue, 2014-09-16 at 10:02 +0200, Tamas K Lengyel wrote: > Certainly. The reason we use this in xenaccess is to avoid the user > attempting to set page permissions on pages which don't exist for the > domain. For example, if the user attempts to set page permissions from > gpfn 0 -> (~0-1), it will waste a lot of the hypervisors time. It > won't break anything as non-existent pages are skipped automatically, > and now with the preemption in place it can't DoS the system, but it's > still a reasonable sanity check to perform. It's not a comprehensive > enforcement of 'don't try to set permission on non-existent pages' as > ARM has holes in the memory layout and doesn't start from 0, but this > check at least works for both x86 and ARM. OK. Please can you include this in the commit message.