From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@citrix.com>
Subject: Re: [PATCH v5 2/4] xen/arm: introduce a generic p2m
 walker and use it in p2m_lookup
Date: Tue, 10 Sep 2013 19:38:55 +0100
Message-ID: <1378838335.3057.43.camel@dagon.hellion.org.uk>
References: <alpine.DEB.2.02.1309091701140.6397@kaball.uk.xensource.com>
	<1378742763-24299-2-git-send-email-stefano.stabellini@eu.citrix.com>
	<1378805207.21748.48.camel@kazak.uk.xensource.com>
	<alpine.DEB.2.02.1309101847080.32236@kaball.uk.xensource.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <alpine.DEB.2.02.1309101847080.32236@kaball.uk.xensource.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: xen-devel@lists.xensource.com, tim@xen.org
List-Id: xen-devel@lists.xenproject.org

On Tue, 2013-09-10 at 19:00 +0100, Stefano Stabellini wrote:
> > > -    /* This bit must be one in the level 3 entry */
> > > -    if ( !pte.p2m.table )
> > > -        pte.bits = 0;
> > > +        if ( cur_first_offset != first_table_offset(paddr) )
> > > +        {
> > > +            if (second) unmap_domain_page(second);
> > > +            second = map_domain_page(first[first_table_offset(paddr)].p2m.base);
> > > +            cur_first_offset = first_table_offset(paddr);
> > > +        }
> > > +        level++;
> > > +        if ( !second ||
> > 
> > ASSERT(second) seems reasonable here, I think, since it would indicate
> > we had screwed up the p2m pretty badly.
> 
> I think it's possible: what if a memory range is simply missing from the
> p2m? The second level pagetable pages could be missing too.

Then the level above it shouldn't have the valid bit set.

Ian.