From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: [PATCH V3] xen: eliminate scalability issues from initial mapping setup Date: Wed, 24 Sep 2014 16:03:45 +0200 Message-ID: <5422CF41.9000803@suse.com> References: <1410965981-15444-1-git-send-email-jgross@suse.com> <1410965981-15444-2-git-send-email-jgross@suse.com> <5422C512.1010602@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5422C512.1010602@citrix.com> Sender: linux-kernel-owner@vger.kernel.org To: David Vrabel , linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, jbeulich@suse.com List-Id: xen-devel@lists.xenproject.org On 09/24/2014 03:20 PM, David Vrabel wrote: > On 17/09/14 15:59, Juergen Gross wrote: >> Direct Xen to place the initial P->M table outside of the initial >> mapping, as otherwise the 1G (implementation) / 2G (theoretical) >> restriction on the size of the initial mapping limits the amount >> of memory a domain can be handed initially. >> >> As the initial P->M table is copied rather early during boot to >> domain private memory and it's initial virtual mapping is dropped, >> the easiest way to avoid virtual address conflicts with other >> addresses in the kernel is to use a user address area for the >> virtual address of the initial P->M table. This allows us to just >> throw away the page tables of the initial mapping after the copy >> without having to care about address invalidation. >> >> It should be noted that this patch won't enable a pv-domain to USE >> more than 512 GB of RAM. It just enables it to be started with a >> P->M table covering more memory. This is especially important for >> being able to boot a Dom0 on a system with more than 512 GB memory. > > This doesn't seem to work. It crashes when attempting to construct > the page tables. Have these patches been tested on a host with > 512 GiB? Not yet. I did a code review and was pretty sure the memory above 512GB would be ignored - seems as if I was wrong. I'll have access to a machine with 1TB RAM soon, so I'll try to test a patch which really does what I thought should be done: ignoring the memory above 512GB. Thanks for testing! Juergen