From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751901AbeFAMYX (ORCPT ); Fri, 1 Jun 2018 08:24:23 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751792AbeFAMYS (ORCPT ); Fri, 1 Jun 2018 08:24:18 -0400 Date: Fri, 1 Jun 2018 14:24:10 +0200 From: Igor Mammedov To: Pankaj Gupta Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org, linux-mm@kvack.org, kwolf@redhat.com, haozhong.zhang@intel.com, jack@suse.cz, xiaoguangrong.eric@gmail.com, riel@surriel.com, niteshnarayanlal@hotmail.com, david@redhat.com, ross.zwisler@intel.com, lcapitulino@redhat.com, hch@infradead.org, mst@redhat.com, stefanha@redhat.com, marcel@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, nilal@redhat.com Subject: Re: [Qemu-devel] [RFC v2 0/2] kvm "fake DAX" device flushing Message-ID: <20180601142410.5c986f13@redhat.com> In-Reply-To: <20180425112415.12327-1-pagupta@redhat.com> References: <20180425112415.12327-1-pagupta@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 25 Apr 2018 16:54:12 +0530 Pankaj Gupta wrote: [...] > - Qemu virtio-pmem device > It exposes a persistent memory range to KVM guest which > at host side is file backed memory and works as persistent > memory device. In addition to this it provides virtio > device handling of flushing interface. KVM guest performs > Qemu side asynchronous sync using this interface. a random high level question, Have you considered using a separate (from memory itself) virtio device as controller for exposing some memory, async flushing. And then just slaving pc-dimm devices to it with notification/ACPI code suppressed so that guest won't touch them? That way it might be more scale-able, you consume only 1 PCI slot for controller vs multiple for virtio-pmem devices. > Changes from previous RFC[1]: > > - Reuse existing 'pmem' code for registering persistent > memory and other operations instead of creating an entirely > new block driver. > - Use VIRTIO driver to register memory information with > nvdimm_bus and create region_type accordingly. > - Call VIRTIO flush from existing pmem driver. > > Details of project idea for 'fake DAX' flushing interface is > shared [2] & [3]. > > Pankaj Gupta (2): > Add virtio-pmem guest driver > pmem: device flush over VIRTIO > > [1] https://marc.info/?l=linux-mm&m=150782346802290&w=2 > [2] https://www.spinics.net/lists/kvm/msg149761.html > [3] https://www.spinics.net/lists/kvm/msg153095.html > > drivers/nvdimm/region_devs.c | 7 ++ > drivers/virtio/Kconfig | 12 +++ > drivers/virtio/Makefile | 1 > drivers/virtio/virtio_pmem.c | 118 +++++++++++++++++++++++++++++++++++++++ > include/linux/libnvdimm.h | 4 + > include/uapi/linux/virtio_ids.h | 1 > include/uapi/linux/virtio_pmem.h | 58 +++++++++++++++++++ > 7 files changed, 201 insertions(+) >