From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH for-4.5 v6 10/17] xen/arm: p2m type definitions and changes Date: Mon, 15 Sep 2014 23:35:55 +0100 Message-ID: <1410820555.6908.14.camel@hastur.hellion.org.uk> References: <1410789775-24197-1-git-send-email-tklengyel@sec.in.tum.de> <1410789775-24197-11-git-send-email-tklengyel@sec.in.tum.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1410789775-24197-11-git-send-email-tklengyel@sec.in.tum.de> 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@xen.org, julien.grall@linaro.org, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, stefano.stabellini@citrix.com, andres@lagarcavilla.org, jbeulich@suse.com, dgdegra@tycho.nsa.gov List-Id: xen-devel@lists.xenproject.org On Mon, 2014-09-15 at 16:02 +0200, Tamas K Lengyel wrote: > Define p2m_access_t in ARM and add necessary changes for page table > construction routines to pass the default access information. Also, > define the Radix tree that will hold access permission settings as > the PTE's don't have enough software programmable bits available. So my main concern here is the overhead for non-xenaccess users. I think it amounts to a few extra fields in the p2m_domain struct which I can see here and presumably some NULL vs. non-NULL type checks which I guess we will get to later. The important thing is that the fast paths for the common case don't get a lot of extra overhead. WRT the xenaccess performance did you consider any options other than a radix tree (which seems quite expensive to me)? e.g. perhaps allocating (only when needed) as second page for each real T page as a shadow/extended region? Perhaps pointed to by a filed in the real PT struct page_info. I'm sure there are other possible ideas too. Ian,