From patchwork Sat Oct 13 05:00:19 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Pankaj Gupta X-Patchwork-Id: 10639931 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6FB31112B for ; Sat, 13 Oct 2018 05:00:46 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5247E2B758 for ; Sat, 13 Oct 2018 05:00:46 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 43ED62B761; Sat, 13 Oct 2018 05:00:46 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BFEBF2B758 for ; Sat, 13 Oct 2018 05:00:45 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 87B7721173C65; Fri, 12 Oct 2018 22:00:45 -0700 (PDT) X-Original-To: linux-nvdimm@ml01.01.org Delivered-To: linux-nvdimm@ml01.01.org Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=pagupta@redhat.com; receiver=linux-nvdimm@ml01.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 88F5F21173C62 for ; Fri, 12 Oct 2018 22:00:43 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 05289D7E6A; Sat, 13 Oct 2018 05:00:43 +0000 (UTC) Received: from dhcp201-121.englab.pnq.redhat.com (dhcp193-42.pnq.redhat.com [10.65.193.42]) by smtp.corp.redhat.com (Postfix) with ESMTP id C7A921C921; Sat, 13 Oct 2018 05:00:23 +0000 (UTC) From: Pankaj Gupta To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org Subject: [PATCH v2 0/2] kvm "fake DAX" device Date: Sat, 13 Oct 2018 10:30:19 +0530 Message-Id: <20181013050021.11962-1-pagupta@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Sat, 13 Oct 2018 05:00:43 +0000 (UTC) X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, jack@suse.cz, xiaoguangrong.eric@gmail.com, riel@surriel.com, david@redhat.com, lcapitulino@redhat.com, hch@infradead.org, imammedo@redhat.com, mst@redhat.com, stefanha@redhat.com, zwisler@kernel.org, pbonzini@redhat.com, nilal@redhat.com, eblake@redhat.com Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Virus-Scanned: ClamAV using ClamSMTP This patch series has implementation for "fake DAX". "fake DAX" is fake persistent memory(nvdimm) in guest which allows to bypass the guest page cache. This also implements a VIRTIO based asynchronous flush mechanism. Sharing guest kernel driver in this patchset with the changes suggested in v1. Tested with Qemu side device emulation for virtio-pmem [4]. Details of project idea for 'fake DAX' flushing interface is shared [2] & [3]. Implementation is divided into two parts: New virtio pmem guest driver and qemu code changes for new virtio pmem paravirtualized device. 1. Guest virtio-pmem kernel driver --------------------------------- - Reads persistent memory range from paravirt device and registers with 'nvdimm_bus'. - 'nvdimm/pmem' driver uses this information to allocate persistent memory region and setup filesystem operations to the allocated memory. - virtio pmem driver implements asynchronous flushing interface to flush from guest to host. 2. Qemu virtio-pmem device --------------------------------- - Creates virtio pmem device and exposes a memory range to KVM guest. - At host side this is file backed memory which acts as persistent memory. - Qemu side flush uses aio thread pool API's and virtio for asynchronous guest multi request handling. David Hildenbrand CCed also posted a modified version[5] of qemu virtio-pmem code based on updated Qemu memory device API. Virtio-pmem errors handling: ---------------------------------------- Checked behaviour of virtio-pmem for below types of errors Need suggestions on expected behaviour for handling these errors? - Hardware Errors: Uncorrectable recoverable Errors: a] virtio-pmem: - As per current logic if error page belongs to Qemu process, host MCE handler isolates(hwpoison) that page and send SIGBUS. Qemu SIGBUS handler injects exception to KVM guest. - KVM guest then isolates the page and send SIGBUS to guest userspace process which has mapped the page. b] Existing implementation for ACPI pmem driver: - Handles such errors with MCE notifier and creates a list of bad blocks. Read/direct access DAX operation return EIO if accessed memory page fall in bad block list. - It also starts backgound scrubbing. - Similar functionality can be reused in virtio-pmem with MCE notifier but without scrubbing(no ACPI/ARS)? Need inputs to confirm if this behaviour is ok or needs any change? Changes from PATCH v1: [1] - 0-day build test for build dependency on libnvdimm Changes suggested by - [Dan Williams] - Split the driver into two parts virtio & pmem - Move queuing of async block request to block layer - Add "sync" parameter in nvdimm_flush function - Use indirect call for nvdimm_flush - Don’t move declarations to common global header e.g nd.h - nvdimm_flush() return 0 or -EIO if it fails - Teach nsio_rw_bytes() that the flush can fail - Rename nvdimm_flush() to generic_nvdimm_flush() - Use 'nd_region->provider_data' for long dereferencing - Remove virtio_pmem_freeze/restore functions - Remove BSD license text with SPDX license text - Add might_sleep() in virtio_pmem_flush - [Luiz] - Make spin_lock_irqsave() narrow Changes from RFC v3 - Rebase to latest upstream - Luiz - Call ndregion->flush in place of nvdimm_flush- Luiz - kmalloc return check - Luiz - virtqueue full handling - Stefan - Don't map entire virtio_pmem_req to device - Stefan - request leak, correct sizeof req- Stefan - Move declaration to virtio_pmem.c Changes from RFC v2: - Add flush function in the nd_region in place of switching on a flag - Dan & Stefan - Add flush completion function with proper locking and wait for host side flush completion - Stefan & Dan - Keep userspace API in uapi header file - Stefan, MST - Use LE fields & New device id - MST - Indentation & spacing suggestions - MST & Eric - Remove extra header files & add licensing - Stefan Changes from RFC v1: - 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. Pankaj Gupta (2): libnvdimm: nd_region flush callback support virtio-pmem: Add virtio-pmem guest driver [1] https://lkml.org/lkml/2018/8/31/407 [2] https://www.spinics.net/lists/kvm/msg149761.html [3] https://www.spinics.net/lists/kvm/msg153095.html [4] https://lkml.org/lkml/2018/8/31/413 [5] https://marc.info/?l=qemu-devel&m=153555721901824&w=2 drivers/acpi/nfit/core.c | 8 ++-- drivers/nvdimm/claim.c | 12 ++++-- drivers/nvdimm/nd.h | 2 + drivers/nvdimm/pmem.c | 24 +++++++++---- drivers/nvdimm/region_devs.c | 76 ++++++++++++++++++++++++++++++++++++++++--- include/linux/libnvdimm.h | 10 ++++- 6 files changed, 110 insertions(+), 22 deletions(-)