From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luiz Capitulino Subject: Re: [Qemu-devel] [RFC v3 2/2] virtio-pmem: Add virtio pmem driver Date: Mon, 16 Jul 2018 10:03:11 -0400 Message-ID: <20180716100311.0149c873@doriath> References: <20180713075232.9575-1-pagupta@redhat.com> <20180713075232.9575-3-pagupta@redhat.com> <20180713163827.74e9fc91@doriath> <633297685.51039804.1531741590092.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <633297685.51039804.1531741590092.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Pankaj Gupta Cc: kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, jack-AlSwsSmVLrQ@public.gmane.org, xiaoguangrong eric , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org, linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org, david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, ross zwisler , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, niteshnarayanlal-PkbjNfxxIARBDgjK7y7TUQ@public.gmane.org, imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org List-Id: linux-nvdimm@lists.01.org On Mon, 16 Jul 2018 07:46:30 -0400 (EDT) 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? > > To avoid interrupt for VQ trying to take same spinlock already taken by process > context and resulting in deadlock. Looks like interrupts are already disabled in > function call, see [1]. But still to protect with any future work. > > [1] > vp_interrupt > vp_vring_interrupt > vring_interrupt I think you're right, and I think I may have caused some confusion. See below. > > > > > +} > > > + /* 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. > > Will add it. > > > > > + > > > + 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() > > Yes, GFP_ATOMIC should be right thing. > > > > > 2. If virtio_pmem_flush() is never called with interrupts disabled, do > > you really need to disable interrupts? If yes, why? > > Same reason as discussed above. Data is shared between interrupt handler > and process context 'virtio-pmem_flush' function. To avoid a deadlock resulting > between interrupt context and process context on same spinlock. > > > > > 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(). > > I think 'virtio_pmem_flush' can be called from atomic context. If you're certain of this, then everything I said in my previous email should be correct (ie. GFP_ATOMIC in kmalloc() and the fact that you can't sleep). Now, if for some reason virtio_pmem_flush() is not called from atomic context (say, because it's never called from the ACPI code), then my review was wrong and I think your code is correct, since you're disabling irqs to protect the virtqueue against the interrupt handler. In this case you can sleep outside the atomic context. > > Thanks, > Pankaj > > > > > > + > > > + 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 > > > > > > >