Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752170AbcJKFxE (ORCPT ); Tue, 11 Oct 2016 01:53:04 -0400 Received: from mga07.intel.com ([134.134.136.100]:54747 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751288AbcJKFxC (ORCPT ); Tue, 11 Oct 2016 01:53:02 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,476,1473145200"; d="scan'208";a="18277100" Date: Tue, 11 Oct 2016 13:52:58 +0800 From: Haozhong Zhang To: Andrew Cooper Cc: , , Juergen Gross , Xiao Guangrong , Andrew Morton , Arnd Bergmann , Johannes Thumshirn , , Stefano Stabellini , David Vrabel , Ross Zwisler , Boris Ostrovsky , Dan Williams Subject: Re: [Xen-devel] [RFC KERNEL PATCH 0/2] Add Dom0 NVDIMM support for Xen Message-ID: <20161011055258.2v67idzs5kjtfs4q@hz-desktop> Mail-Followup-To: Andrew Cooper , , , Juergen Gross , Xiao Guangrong , Andrew Morton , Arnd Bergmann , Johannes Thumshirn , , Stefano Stabellini , David Vrabel , Ross Zwisler , Boris Ostrovsky , Dan Williams References: <20161010003523.4423-1-haozhong.zhang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20160827 (1.7.0) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2693 Lines: 64 On 10/10/16 17:43, Andrew Cooper wrote: > 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. ACPI specification does not require them to appear in E820, though it defines E820 type-7 for persistent memory. > > 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? > For NVDIMM devices already plugged at power on, their MFN information can be got from NFIT table. However, MFN information for hotplugged NVDIMM devices should be got via AML _FIT method, so point 2) is needed. > > 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. > Do you mean to treat them as mmio pages of type p2m_mmio_direct and map them to guest by map_mmio_regions()? Thanks, Haozhong