Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753123AbcJJQr2 (ORCPT ); Mon, 10 Oct 2016 12:47:28 -0400 Received: from smtp.ctxuk.citrix.com ([185.25.65.24]:22636 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752316AbcJJQr1 (ORCPT ); Mon, 10 Oct 2016 12:47:27 -0400 X-IronPort-AV: E=Sophos;i="5.31,325,1473120000"; d="scan'208";a="32787077" Subject: Re: [Xen-devel] [RFC KERNEL PATCH 0/2] Add Dom0 NVDIMM support for Xen To: Haozhong Zhang , , References: <20161010003523.4423-1-haozhong.zhang@intel.com> CC: Juergen Gross , Xiao Guangrong , Andrew Morton , Arnd Bergmann , Johannes Thumshirn , , Stefano Stabellini , David Vrabel , Ross Zwisler , Boris Ostrovsky , Dan Williams From: Andrew Cooper Message-ID: Date: Mon, 10 Oct 2016 17:43:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.3.0 MIME-Version: 1.0 In-Reply-To: <20161010003523.4423-1-haozhong.zhang@intel.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL02.citrite.net (10.69.22.126) X-DLP: AMS1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2111 Lines: 49 On 10/10/16 01:35, Haozhong Zhang wrote: > Overview > ======== > This RFC kernel patch series along with corresponding patch series of > Xen, QEMU and ndctl implements Xen vNVDIMM, which can map the host > NVDIMM devices to Xen HVM domU as vNVDIMM devices. > > Xen hypervisor does not include an NVDIMM driver, so it needs the > assistance from the driver in Dom0 Linux kernel to manage NVDIMM > devices. We currently only supports NVDIMM devices in pmem mode. > > Design and Implementation > ========================= > The complete design can be found at > https://lists.xenproject.org/archives/html/xen-devel/2016-07/msg01921.html. > > All patch series can be found at > Xen: https://github.com/hzzhan9/xen.git nvdimm-rfc-v1 > QEMU: https://github.com/hzzhan9/qemu.git xen-nvdimm-rfc-v1 > Linux kernel: https://github.com/hzzhan9/nvdimm.git xen-nvdimm-rfc-v1 > ndctl: https://github.com/hzzhan9/ndctl.git pfn-xen-rfc-v1 > > 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. Please can we take a step back here before diving down a rabbit hole. How do pblk/pmem regions appear in the E820 map at boot? At the very least, I would expect at least a large reserved region. Is the MFN information (SPA in your terminology, so far as I can tell) available in any static APCI tables, or are they only available as a result of executing AML methods? If the MFN information is only available via AML, then point 2) is needed, although the reporting back to Xen should be restricted to a xen component, rather than polluting the main device driver. 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. ~Andrew