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[209.132.180.67]) by mx.google.com with ESMTP id f12-v6si22685214pgq.559.2018.07.13.13.51.47; Fri, 13 Jul 2018 13:52:02 -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 S1731949AbeGMVH1 (ORCPT + 99 others); Fri, 13 Jul 2018 17:07:27 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:43334 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731342AbeGMVH1 (ORCPT ); Fri, 13 Jul 2018 17:07:27 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D34491698E; Fri, 13 Jul 2018 20:51:08 +0000 (UTC) Received: from doriath (ovpn-117-239.phx2.redhat.com [10.3.117.239]) by smtp.corp.redhat.com (Postfix) with ESMTP id 24A49111DD1F; Fri, 13 Jul 2018 20:50:56 +0000 (UTC) Date: Fri, 13 Jul 2018 16:38:27 -0400 From: Luiz Capitulino To: Pankaj Gupta Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org, jack@suse.cz, stefanha@redhat.com, dan.j.williams@intel.com, riel@surriel.com, haozhong.zhang@intel.com, nilal@redhat.com, kwolf@redhat.com, pbonzini@redhat.com, ross.zwisler@intel.com, david@redhat.com, xiaoguangrong.eric@gmail.com, hch@infradead.org, mst@redhat.com, niteshnarayanlal@hotmail.com, imammedo@redhat.com, eblake@redhat.com Subject: Re: [RFC v3 2/2] virtio-pmem: Add virtio pmem driver Message-ID: <20180713163827.74e9fc91@doriath> In-Reply-To: <20180713075232.9575-3-pagupta@redhat.com> References: <20180713075232.9575-1-pagupta@redhat.com> <20180713075232.9575-3-pagupta@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Fri, 13 Jul 2018 20:51:08 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Fri, 13 Jul 2018 20:51:08 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'lcapitulino@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 13 Jul 2018 13:22:31 +0530 Pankaj Gupta wrote: > 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 | 190 +++++++++++++++++++++++++++++++++++++++ > include/linux/virtio_pmem.h | 44 +++++++++ > include/uapi/linux/virtio_ids.h | 1 + > include/uapi/linux/virtio_pmem.h | 40 +++++++++ > 6 files changed, 285 insertions(+) > create mode 100644 drivers/virtio/virtio_pmem.c > create mode 100644 include/linux/virtio_pmem.h > 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..6200b5e > --- /dev/null > +++ b/drivers/virtio/virtio_pmem.c > @@ -0,0 +1,190 @@ > +// 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 > + > +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; > + 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->acked); > + } > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags); Honest question: why do you need to disable interrupts here? > +} > + /* 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); > + > + return 0; > +}; > + > + /* The request submission function */ > +static int virtio_pmem_flush(struct device *dev) > +{ > + int err; > + unsigned long flags; > + struct scatterlist *sgs[2], sg, ret; > + struct virtio_device *vdev = dev_to_virtio(dev->parent->parent); > + struct virtio_pmem *vpmem = vdev->priv; > + struct virtio_pmem_request *req = kmalloc(sizeof(*req), GFP_KERNEL); Not checking kmalloc() return. > + > + req->done = false; > + init_waitqueue_head(&req->acked); > + spin_lock_irqsave(&vpmem->pmem_lock, flags); Why do you need spin_lock_irqsave()? There are two points consider: 1. Will virtio_pmem_flush() ever be called with interrupts disabled? If yes, then it's broken since you should be using GFP_ATOMIC in the kmalloc() call and you can't call wait_event() 2. If virtio_pmem_flush() is never called with interrupts disabled, do you really need to disable interrupts? If yes, why? Another point to consider is whether or not virtio_pmem_flush() can be called from atomic context. nvdimm_flush() itself is called from a few atomic sites, but I can't tell if virtio_pmem_flush() will ever be called from those sites. If it can be called atomic context, then item 1 applies here. If you're sure it can't, then you should probably call might_sleep(). > + > + sg_init_one(&sg, req, sizeof(req)); > + 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"); > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags); > + return -ENOSPC; > + } > + 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->acked, req->done); > + err = req->ret; > + kfree(req); > + > + return err; > +}; > + > +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 > + > + > +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/linux/virtio_pmem.h b/include/linux/virtio_pmem.h > new file mode 100644 > index 0000000..0f83d9c > --- /dev/null > +++ b/include/linux/virtio_pmem.h > @@ -0,0 +1,44 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * virtio_pmem.h: virtio pmem Driver > + * > + * Discovers persistent memory range information > + * from host and provides a virtio based flushing > + * interface. > + */ > +#ifndef _LINUX_VIRTIO_PMEM_H > +#define _LINUX_VIRTIO_PMEM_H > + > +#include > +#include > +#include > +#include > +#include > + > +struct virtio_pmem_request { > + /* Host return status corresponding to flush request */ > + int ret; > + > + /* Wait queue to process deferred work after ack from host */ > + wait_queue_head_t acked; > + bool done; > +}; > + > +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; > + > + /* Synchronize virtqueue data */ > + spinlock_t pmem_lock; > + > + /* Memory region information */ > + uint64_t start; > + uint64_t size; > +}; > +#endif > 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: > + * > + * > + * 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