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[209.132.180.67]) by mx.google.com with ESMTP id a8-v6si1610343pgm.331.2018.09.24.03.04.36; Mon, 24 Sep 2018 03:04:52 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727477AbeIXPnO (ORCPT + 99 others); Mon, 24 Sep 2018 11:43:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48318 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725982AbeIXPnO (ORCPT ); Mon, 24 Sep 2018 11:43:14 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BFF6A7F6A0; Mon, 24 Sep 2018 09:42:01 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A3519379F; Mon, 24 Sep 2018 09:42:01 +0000 (UTC) Received: from zmail21.collab.prod.int.phx2.redhat.com (zmail21.collab.prod.int.phx2.redhat.com [10.5.83.24]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 6C0161808855; Mon, 24 Sep 2018 09:42:00 +0000 (UTC) Date: Mon, 24 Sep 2018 05:41:59 -0400 (EDT) From: Pankaj Gupta To: Dan Williams Cc: Linux Kernel Mailing List , KVM list , Qemu Developers , linux-nvdimm , Jan Kara , Stefan Hajnoczi , Rik van Riel , Nitesh Narayan Lal , Kevin Wolf , Paolo Bonzini , Ross Zwisler , David Hildenbrand , Xiao Guangrong , Christoph Hellwig , "Michael S. Tsirkin" , niteshnarayanlal@hotmail.com, lcapitulino@redhat.com, Igor Mammedov , Eric Blake Message-ID: <1204243972.15515798.1537782119951.JavaMail.zimbra@redhat.com> In-Reply-To: References: <20180831133019.27579-1-pagupta@redhat.com> <20180831133019.27579-4-pagupta@redhat.com> Subject: Re: [PATCH 3/3] virtio-pmem: Add virtio pmem driver MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.65.193.131, 10.4.195.6] Thread-Topic: virtio-pmem: Add virtio pmem driver Thread-Index: O2xK7RuQHwBLvgXctDUcgKgtPS87Ew== X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Mon, 24 Sep 2018 09:42:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dan, Thanks for the review. Please find my reply inline. > > This patch adds virtio-pmem driver for KVM guest. > > > > Guest reads the persistent memory range information from > > Qemu over VIRTIO and registers it on nvdimm_bus. It also > > creates a nd_region object with the persistent memory > > range information so that existing 'nvdimm/pmem' driver > > can reserve this into system memory map. This way > > 'virtio-pmem' driver uses existing functionality of pmem > > driver to register persistent memory compatible for DAX > > capable filesystems. > > > > This also provides function to perform guest flush over > > VIRTIO from 'pmem' driver when userspace performs flush > > on DAX memory range. > > > > Signed-off-by: Pankaj Gupta > > --- > > drivers/virtio/Kconfig | 9 ++ > > drivers/virtio/Makefile | 1 + > > drivers/virtio/virtio_pmem.c | 255 > > +++++++++++++++++++++++++++++++++++++++ > > include/uapi/linux/virtio_ids.h | 1 + > > include/uapi/linux/virtio_pmem.h | 40 ++++++ > > 5 files changed, 306 insertions(+) > > create mode 100644 drivers/virtio/virtio_pmem.c > > create mode 100644 include/uapi/linux/virtio_pmem.h > > > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > > index 3589764..a331e23 100644 > > --- a/drivers/virtio/Kconfig > > +++ b/drivers/virtio/Kconfig > > @@ -42,6 +42,15 @@ config VIRTIO_PCI_LEGACY > > > > If unsure, say Y. > > > > +config VIRTIO_PMEM > > + tristate "Support for virtio pmem driver" > > + depends on VIRTIO > > + help > > + This driver provides support for virtio based flushing interface > > + for persistent memory range. > > + > > + If unsure, say M. > > + > > config VIRTIO_BALLOON > > tristate "Virtio balloon driver" > > depends on VIRTIO > > diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile > > index 3a2b5c5..cbe91c6 100644 > > --- a/drivers/virtio/Makefile > > +++ b/drivers/virtio/Makefile > > @@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o > > virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o > > obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o > > obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o > > +obj-$(CONFIG_VIRTIO_PMEM) += virtio_pmem.o > > diff --git a/drivers/virtio/virtio_pmem.c b/drivers/virtio/virtio_pmem.c > > new file mode 100644 > > index 0000000..c22cc87 > > --- /dev/null > > +++ b/drivers/virtio/virtio_pmem.c > > @@ -0,0 +1,255 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * virtio_pmem.c: Virtio pmem Driver > > + * > > + * Discovers persistent memory range information > > + * from host and provides a virtio based flushing > > + * interface. > > + */ > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > I think we need to split this driver into 2 files, > drivers/virtio/pmem.c would discover and register the virtual pmem > device with the libnvdimm core, and drivers/nvdimm/virtio.c would > house virtio_pmem_flush(). o.k. Will split the driver into two files as suggested. > > > + > > +struct virtio_pmem_request { > > + /* Host return status corresponding to flush request */ > > + int ret; > > + > > + /* command name*/ > > + char name[16]; > > + > > + /* Wait queue to process deferred work after ack from host */ > > + wait_queue_head_t host_acked; > > + bool done; > > + > > + /* Wait queue to process deferred work after virt queue buffer > > avail */ > > + wait_queue_head_t wq_buf; > > Why does this need wait_queue's per request? shouldn't this be per-device? This is used to wait flush calling threads when virtio queue is full. wait_queue in request struct binds waitqueue and request. When host acknowledges guest, first waiting request is selected and corresponding thread is woken-up. Alternatively, we can use "add_wait_queue_exclusive" with device wait_queue. This will wake up only one exclusive process waiting. This will avoid using additional list for tracking. > > > + bool wq_buf_avail; > > + struct list_head list; > > +}; > > + > > +struct virtio_pmem { > > + struct virtio_device *vdev; > > + > > + /* Virtio pmem request queue */ > > + struct virtqueue *req_vq; > > + > > + /* nvdimm bus registers virtio pmem device */ > > + struct nvdimm_bus *nvdimm_bus; > > + struct nvdimm_bus_descriptor nd_desc; > > + > > + /* List to store deferred work if virtqueue is full */ > > + struct list_head req_list; > > + > > + /* Synchronize virtqueue data */ > > + spinlock_t pmem_lock; > > + > > + /* Memory region information */ > > + uint64_t start; > > + uint64_t size; > > +}; > > + > > +static struct virtio_device_id id_table[] = { > > + { VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID }, > > + { 0 }, > > +}; > > + > > + /* The interrupt handler */ > > +static void host_ack(struct virtqueue *vq) > > +{ > > + unsigned int len; > > + unsigned long flags; > > + struct virtio_pmem_request *req, *req_buf; > > + struct virtio_pmem *vpmem = vq->vdev->priv; > > + > > + spin_lock_irqsave(&vpmem->pmem_lock, flags); > > + while ((req = virtqueue_get_buf(vq, &len)) != NULL) { > > + req->done = true; > > + wake_up(&req->host_acked); > > + > > + if (!list_empty(&vpmem->req_list)) { > > + req_buf = list_first_entry(&vpmem->req_list, > > + struct virtio_pmem_request, list); > > + list_del(&vpmem->req_list); > > + req_buf->wq_buf_avail = true; > > + wake_up(&req_buf->wq_buf); > > + } > > + } > > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags); > > +} > > + /* Initialize virt queue */ > > +static int init_vq(struct virtio_pmem *vpmem) > > +{ > > + struct virtqueue *vq; > > + > > + /* single vq */ > > + vpmem->req_vq = vq = virtio_find_single_vq(vpmem->vdev, > > + host_ack, "flush_queue"); > > + if (IS_ERR(vq)) > > + return PTR_ERR(vq); > > + > > + spin_lock_init(&vpmem->pmem_lock); > > + INIT_LIST_HEAD(&vpmem->req_list); > > + > > + return 0; > > +}; > > + > > + /* The request submission function */ > > +static int virtio_pmem_flush(struct nd_region *nd_region) > > +{ > > + int err; > > + unsigned long flags; > > + struct scatterlist *sgs[2], sg, ret; > > + struct virtio_device *vdev = > > + dev_to_virtio(nd_region->dev.parent->parent); > > That's a long de-ref chain I would just stash the vdev in > nd_region->provider_data. Sure. Will use 'nd_region->provider_data' for vdev. > > > + struct virtio_pmem *vpmem = vdev->priv; > > + struct virtio_pmem_request *req = kmalloc(sizeof(*req), > > GFP_KERNEL); > > + > > + if (!req) > > + return -ENOMEM; > > + > > + req->done = req->wq_buf_avail = false; > > + strcpy(req->name, "FLUSH"); > > + init_waitqueue_head(&req->host_acked); > > + init_waitqueue_head(&req->wq_buf); > > + > > + spin_lock_irqsave(&vpmem->pmem_lock, flags); > > + sg_init_one(&sg, req->name, strlen(req->name)); > > + sgs[0] = &sg; > > + sg_init_one(&ret, &req->ret, sizeof(req->ret)); > > + sgs[1] = &ret; > > + err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC); > > + if (err) { > > + dev_err(&vdev->dev, "failed to send command to virtio pmem > > device\n"); > > + > > + list_add_tail(&vpmem->req_list, &req->list); > > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags); > > + > > + /* When host has read buffer, this completes via host_ack > > */ > > + wait_event(req->wq_buf, req->wq_buf_avail); > > + spin_lock_irqsave(&vpmem->pmem_lock, flags); > > + } > > + virtqueue_kick(vpmem->req_vq); > > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags); > > + > > + /* When host has read buffer, this completes via host_ack */ > > + wait_event(req->host_acked, req->done); > > Hmm, this seems awkward if this is called from pmem_make_request. If > we need to wait for completion that should be managed by the guest > block layer. I.e. make_request should just queue request and then > trigger bio_endio() when the response comes back. We are plugging VIRTIO based flush callback for virtio_pmem driver. If pmem driver (pmem_make_request) has to queue request we have to plug "blk_mq_ops" callbacks for corresponding VIRTIO vqs. AFAICU there is no existing multiqueue code merged for pmem driver yet, though i could see patches by Dave upstream. Anything I am missing here? > > However this does mean that nvdimm_flush() becomes asynchronous. So > maybe we need to pass in a 'sync' flag or the bio directly to indicate > this is an asynchronous flush request from pmem_make_request() vs a > synchronous one from nsio_rw_bytes(). Sure. > > > + err = req->ret; > > + kfree(req); > > + > > + return err; > > +}; > > +EXPORT_SYMBOL_GPL(virtio_pmem_flush); > > + > > +static int virtio_pmem_probe(struct virtio_device *vdev) > > +{ > > + int err = 0; > > + struct resource res; > > + struct virtio_pmem *vpmem; > > + struct nvdimm_bus *nvdimm_bus; > > + struct nd_region_desc ndr_desc; > > + int nid = dev_to_node(&vdev->dev); > > + struct nd_region *nd_region; > > + > > + if (!vdev->config->get) { > > + dev_err(&vdev->dev, "%s failure: config disabled\n", > > + __func__); > > + return -EINVAL; > > + } > > + > > + vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem), > > + GFP_KERNEL); > > + if (!vpmem) { > > + err = -ENOMEM; > > + goto out_err; > > + } > > + > > + vpmem->vdev = vdev; > > + err = init_vq(vpmem); > > + if (err) > > + goto out_err; > > + > > + virtio_cread(vpmem->vdev, struct virtio_pmem_config, > > + start, &vpmem->start); > > + virtio_cread(vpmem->vdev, struct virtio_pmem_config, > > + size, &vpmem->size); > > + > > + res.start = vpmem->start; > > + res.end = vpmem->start + vpmem->size-1; > > + vpmem->nd_desc.provider_name = "virtio-pmem"; > > + vpmem->nd_desc.module = THIS_MODULE; > > + > > + vpmem->nvdimm_bus = nvdimm_bus = nvdimm_bus_register(&vdev->dev, > > + &vpmem->nd_desc); > > + if (!nvdimm_bus) > > + goto out_vq; > > + > > + dev_set_drvdata(&vdev->dev, nvdimm_bus); > > + memset(&ndr_desc, 0, sizeof(ndr_desc)); > > + > > + ndr_desc.res = &res; > > + ndr_desc.numa_node = nid; > > + ndr_desc.flush = virtio_pmem_flush; > > + set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags); > > + nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc); > > + > > + if (!nd_region) > > + goto out_nd; > > + > > + //virtio_device_ready(vdev); > > + return 0; > > +out_nd: > > + err = -ENXIO; > > + nvdimm_bus_unregister(nvdimm_bus); > > +out_vq: > > + vdev->config->del_vqs(vdev); > > +out_err: > > + dev_err(&vdev->dev, "failed to register virtio pmem memory\n"); > > + return err; > > +} > > + > > +static void virtio_pmem_remove(struct virtio_device *vdev) > > +{ > > + struct virtio_pmem *vpmem = vdev->priv; > > + struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev); > > + > > + nvdimm_bus_unregister(nvdimm_bus); > > + vdev->config->del_vqs(vdev); > > + kfree(vpmem); > > +} > > + > > +#ifdef CONFIG_PM_SLEEP > > +static int virtio_pmem_freeze(struct virtio_device *vdev) > > +{ > > + /* todo: handle freeze function */ > > + return -EPERM; > > +} > > + > > +static int virtio_pmem_restore(struct virtio_device *vdev) > > +{ > > + /* todo: handle restore function */ > > + return -EPERM; > > +} > > +#endif > > As far as I can see there's nothing to do on a power transition, I > would just omit this completely. o.k Will remove these handlers. > > > + > > + > > +static struct virtio_driver virtio_pmem_driver = { > > + .driver.name = KBUILD_MODNAME, > > + .driver.owner = THIS_MODULE, > > + .id_table = id_table, > > + .probe = virtio_pmem_probe, > > + .remove = virtio_pmem_remove, > > +#ifdef CONFIG_PM_SLEEP > > + .freeze = virtio_pmem_freeze, > > + .restore = virtio_pmem_restore, > > +#endif > > +}; > > + > > +module_virtio_driver(virtio_pmem_driver); > > +MODULE_DEVICE_TABLE(virtio, id_table); > > +MODULE_DESCRIPTION("Virtio pmem driver"); > > +MODULE_LICENSE("GPL"); > > diff --git a/include/uapi/linux/virtio_ids.h > > b/include/uapi/linux/virtio_ids.h > > index 6d5c3b2..3463895 100644 > > --- a/include/uapi/linux/virtio_ids.h > > +++ b/include/uapi/linux/virtio_ids.h > > @@ -43,5 +43,6 @@ > > #define VIRTIO_ID_INPUT 18 /* virtio input */ > > #define VIRTIO_ID_VSOCK 19 /* virtio vsock transport */ > > #define VIRTIO_ID_CRYPTO 20 /* virtio crypto */ > > +#define VIRTIO_ID_PMEM 25 /* virtio pmem */ > > > > #endif /* _LINUX_VIRTIO_IDS_H */ > > diff --git a/include/uapi/linux/virtio_pmem.h > > b/include/uapi/linux/virtio_pmem.h > > new file mode 100644 > > index 0000000..c7c22a5 > > --- /dev/null > > +++ b/include/uapi/linux/virtio_pmem.h > > @@ -0,0 +1,40 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +/* > > + * This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so > > + * anyone can use the definitions to implement compatible drivers/servers: > > The SPDX identifier does not match this BSD license, and the whole > point of the SPDX identifier is to get out of the need to have these > large text blobs of license goop. Right, just copied this. Will remove these BSD lines. > > > + * > > + * > > + * Redistribution and use in source and binary forms, with or without > > + * modification, are permitted provided that the following conditions > > + * are met: > > + * 1. Redistributions of source code must retain the above copyright > > + * notice, this list of conditions and the following disclaimer. > > + * 2. Redistributions in binary form must reproduce the above copyright > > + * notice, this list of conditions and the following disclaimer in the > > + * documentation and/or other materials provided with the distribution. > > + * 3. Neither the name of IBM nor the names of its contributors > > + * may be used to endorse or promote products derived from this > > software > > + * without specific prior written permission. > > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS > > ``AS IS'' > > + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, > > THE > > + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR > > PURPOSE > > + * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE > > + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR > > CONSEQUENTIAL > > + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS > > + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) > > + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, > > STRICT > > + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY > > WAY > > + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF > > + * SUCH DAMAGE. > > + * > > + * Copyright (C) Red Hat, Inc., 2018-2019 > > + * Copyright (C) Pankaj Gupta , 2018 > > + */ > > +#ifndef _UAPI_LINUX_VIRTIO_PMEM_H > > +#define _UAPI_LINUX_VIRTIO_PMEM_H > > + > > +struct virtio_pmem_config { > > + __le64 start; > > + __le64 size; > > +}; > > +#endif > > Why does this need to be in the uapi? This struct is defined by userspace(Qemu) and used by kernel to fetch values passed by qemu device. Thanks, Pankaj