From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: PV-vNUMA issue: topology is misinterpreted by the guest Date: Mon, 27 Jul 2015 17:31:18 +0100 Message-ID: <55B65CD6.7000607@citrix.com> References: <1437042762.28251.18.camel@citrix.com> <55B64A8A.7040200@citrix.com> <1438012950.5036.215.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZJlJl-0003lZ-9V for xen-devel@lists.xenproject.org; Mon, 27 Jul 2015 16:31:57 +0000 In-Reply-To: <1438012950.5036.215.camel@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: Dario Faggioli Cc: Elena Ufimtseva , Wei Liu , Andrew Cooper , Jan Beulich , "xen-devel@lists.xenproject.org" , Boris Ostrovsky List-Id: xen-devel@lists.xenproject.org On 27/07/15 17:02, Dario Faggioli wrote: > On Mon, 2015-07-27 at 16:13 +0100, David Vrabel wrote: >> On 16/07/15 11:32, Dario Faggioli wrote: >>> >>> Anyway, is there anything we can do to fix or workaround things? >> >> This thread has gotten a bit long... >> > Yep, indeed... :-( > >> For Linux I would like to see: >> >> 1. No support for NUMA in PV guests -- if you want new MM features in a >> guest use HVM. >> > Wow... Really? What about all the code we have in libxl and Xen to deal > exactly with that? What about making it possible to configure vNUMA for > Dom0? I don't think there is any (much?) PV-specific code in Xen/toolstack for this, right? It's common between HVM and PV, yes? I would prefer effort into making a no-dm HVM dom0 work instead because this is a better long-term solution for dom0. That said, if someone does the work for vNUMA in Linux PV guests and it looks sensible and self-contained then I would probably merge it. >> 2. For HVM guests, use the existing hardware interfaces to present NUMA >> topology. i.e., CPUID, ACPI tables etc. This will work for both kernel >> and userspace and both will see the same topology. >> >> This also has the advantage that any hypervisor/toolstack work will also >> be applicable to other guests (e.g., Windows). >> > Yeah, indeed. That's the downside of Juergen's "Linux scheduler > approach". But the issue is there, even without taking vNUMA into > account, and I think something like that would really help (only for > Dom0, and Linux guests, of course). I disagree. Whether we're using vNUMA or not, Xen should still ensure that the guest kernel and userspace see a consistent and correct topology using the native mechanisms. David