Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754512AbcJLHZp convert rfc822-to-8bit (ORCPT ); Wed, 12 Oct 2016 03:25:45 -0400 Received: from prv-mh.provo.novell.com ([137.65.248.74]:42531 "EHLO prv-mh.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754129AbcJLHZj (ORCPT ); Wed, 12 Oct 2016 03:25:39 -0400 Message-Id: <57FE018D020000780011690A@prv-mh.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.2.1 Date: Wed, 12 Oct 2016 01:25:33 -0600 From: "Jan Beulich" To: "Dan Williams" Cc: "Stefano Stabellini" , "Arnd Bergmann" , , "David Vrabel" , "Haozhong Zhang" , "Andrew Morton" , "Xiao Guangrong" , "Ross Zwisler" , "linux-nvdimm@lists.01.org" , , "Boris Ostrovsky" , "Juergen Gross" , "Johannes Thumshirn" , "linux-kernel@vger.kernel.org" Subject: Re: [Xen-devel] [RFC KERNEL PATCH 0/2] Add Dom0 NVDIMM support for Xen References: <20161010003523.4423-1-haozhong.zhang@intel.com> <57FCF26A02000078000F15E0@prv-mh.provo.novell.com> In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1472 Lines: 29 >>> On 11.10.16 at 17:53, wrote: > On Tue, Oct 11, 2016 at 6:08 AM, Jan Beulich wrote: >>>>> Andrew Cooper 10/10/16 6:44 PM >>> >>>On 10/10/16 01:35, Haozhong Zhang wrote: >>>> Xen hypervisor needs assistance from Dom0 Linux kernel for following tasks: >>>> 1) Reserve an area on NVDIMM devices for Xen hypervisor to place >>>> memory management data structures, i.e. frame table and M2P table. >>>> 2) Report SPA ranges of NVDIMM devices and the reserved area to Xen >>>> hypervisor. >>> >>>However, I can't see any justification for 1). Dom0 should not be >>>involved in Xen's management of its own frame table and m2p. The mfns >>>making up the pmem/pblk regions should be treated just like any other >>>MMIO regions, and be handed wholesale to dom0 by default. >> >> That precludes the use as RAM extension, and I thought earlier rounds of >> discussion had got everyone in agreement that at least for the pmem case >> we will need some control data in Xen. > > The missing piece for me is why this reservation for control data > needs to be done in the libnvdimm core? I would expect that any dax > capable file could be mapped and made available to a guest. This > includes /dev/ramX devices that are dax capable, but are external to > the libnvdimm sub-system. Despite me being the only one on the To list, I don't think the question was really meant to be directed to me. Jan