From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp2130.oracle.com ([141.146.126.79]:47906 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729037AbfDJOjo (ORCPT ); Wed, 10 Apr 2019 10:39:44 -0400 Date: Wed, 10 Apr 2019 17:38:26 +0300 From: Yuval Shaia Subject: Re: [PATCH v5 2/5] virtio-pmem: Add virtio pmem driver Message-ID: <20190410143826.GA7856@lap1> References: <20190410040826.24371-1-pagupta@redhat.com> <20190410040826.24371-3-pagupta@redhat.com> <20190410142426.5bf0d9a4.cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190410142426.5bf0d9a4.cohuck@redhat.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Cornelia Huck , pagupta@redhat.com Cc: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-acpi@vger.kernel.org, qemu-devel@nongnu.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, dan.j.williams@intel.com, zwisler@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, mst@redhat.com, jasowang@redhat.com, willy@infradead.org, rjw@rjwysocki.net, hch@infradead.org, lenb@kernel.org, jack@suse.cz, tytso@mit.edu, adilger.kernel@dilger.ca, darrick.wong@oracle.com, lcapitulino@redhat.com, kwolf@redhat.com, imammedo@redhat.com, jmoyer@redhat.com, nilal@redhat.com, riel@surriel.com, stefanha@redhat.com, aarcange@redhat.com, david@redhat.com, david@fromorbit.com, xiaoguangrong.eric@gmail.com, pbonzini@redhat.com, kilobyte@angband.pl On Wed, Apr 10, 2019 at 02:24:26PM +0200, Cornelia Huck wrote: > On Wed, 10 Apr 2019 09:38:22 +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/nvdimm/virtio_pmem.c | 88 ++++++++++++++++++++++ > > drivers/virtio/Kconfig | 10 +++ > > drivers/virtio/Makefile | 1 + > > drivers/virtio/pmem.c | 124 +++++++++++++++++++++++++++++++ > > include/linux/virtio_pmem.h | 60 +++++++++++++++ > > include/uapi/linux/virtio_ids.h | 1 + > > include/uapi/linux/virtio_pmem.h | 10 +++ > > 7 files changed, 294 insertions(+) > > create mode 100644 drivers/nvdimm/virtio_pmem.c > > create mode 100644 drivers/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/pmem.c b/drivers/virtio/pmem.c > > new file mode 100644 > > index 000000000000..cc9de9589d56 > > --- /dev/null > > +++ b/drivers/virtio/pmem.c > > @@ -0,0 +1,124 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * virtio_pmem.c: Virtio pmem Driver > > + * > > + * Discovers persistent memory range information > > + * from host and registers the virtual pmem device > > + * with libnvdimm core. > > + */ > > +#include > > +#include <../../drivers/nvdimm/nd.h> > > + > > +static struct virtio_device_id id_table[] = { > > + { VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID }, > > + { 0 }, > > +}; > > + > > + /* Initialize virt queue */ > > +static int init_vq(struct virtio_pmem *vpmem) > > IMHO, you don't gain much by splitting off this function... It make sense to have all the vq-init-related stuff in one function, so here pmem_lock and req_list are used only for the vq. Saying that - maybe it would be better to have the 3 in one struct. > > > +{ > > + 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); > > I'm personally not a fan of chained assignments... I think I'd just > drop the 'vq' variable and operate on vpmem->req_vq directly. +1 > > > + > > + spin_lock_init(&vpmem->pmem_lock); > > + INIT_LIST_HEAD(&vpmem->req_list); > > + > > + return 0; > > +}; > > + > > +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", > > Maybe s/config disabled/config access disabled/ ? That seems to be the > more common message. > > > + __func__); > > + return -EINVAL; > > + } > > + > > + vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem), > > + GFP_KERNEL); > > Here, the vpmem variable makes sense for convenience, but I'm again not > a fan of the chaining :) +1 > > > + 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); > > And here :) > > > + if (!nvdimm_bus) > > + goto out_vq; > > + > > + dev_set_drvdata(&vdev->dev, nvdimm_bus); > > + > > + ndr_desc.res = &res; > > + ndr_desc.numa_node = nid; > > + ndr_desc.flush = virtio_pmem_flush; > > + set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags); > > + set_bit(ND_REGION_ASYNC, &ndr_desc.flags); > > + nd_region = nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc); > > + nd_region->provider_data = dev_to_virtio > > + (nd_region->dev.parent->parent); > > Isn't it clear that this parent chain will always end up at &vdev->dev? > Maybe simply set ->provider_data to vdev directly? (Does it need to > grab a reference count of the device, BTW?) > > > + > > + if (!nd_region) > > + goto out_nd; > > Probably better to do this check before you access nd_region's > members :) > > > + > > + 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); > > I haven't followed this around the nvdimm code, but is the nd_region > you created during probe cleaned up automatically, or would you need to > do something here? > > > + vdev->config->del_vqs(vdev); > > + vdev->config->reset(vdev); > > + kfree(vpmem); > > You allocated vpmem via devm_kzalloc; isn't it freed automatically on > remove? > > > +} > > + > > +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, > > +}; > > + > > +module_virtio_driver(virtio_pmem_driver); > > +MODULE_DEVICE_TABLE(virtio, id_table); > > +MODULE_DESCRIPTION("Virtio pmem driver"); > > +MODULE_LICENSE("GPL"); > > Only looked at this from the general virtio driver angle; seems fine > apart from some easy-to-fix issues and some personal style preference > things.