> > 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 <pagupta@xxxxxxxxxx>
> > Reviewed-by: Yuval Shaia <yuval.shaia@xxxxxxxxxx>
>
> Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Thank you, Michael.
Best regards,
Pankaj
>
> > ---
> > drivers/nvdimm/Makefile | 1 +
> > drivers/nvdimm/nd_virtio.c | 129 +++++++++++++++++++++++++++++++
> > drivers/nvdimm/virtio_pmem.c | 117 ++++++++++++++++++++++++++++
> > drivers/virtio/Kconfig | 10 +++
> > include/linux/virtio_pmem.h | 60 ++++++++++++++
> > include/uapi/linux/virtio_ids.h | 1 +
> > include/uapi/linux/virtio_pmem.h | 10 +++
> > 7 files changed, 328 insertions(+)
> > create mode 100644 drivers/nvdimm/nd_virtio.c
> > create mode 100644 drivers/nvdimm/virtio_pmem.c
> > create mode 100644 include/linux/virtio_pmem.h
> > create mode 100644 include/uapi/linux/virtio_pmem.h
> >
> > diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
> > index 6f2a088afad6..cefe233e0b52 100644
> > --- a/drivers/nvdimm/Makefile
> > +++ b/drivers/nvdimm/Makefile
> > @@ -5,6 +5,7 @@ obj-$(CONFIG_ND_BTT) += nd_btt.o
> > obj-$(CONFIG_ND_BLK) += nd_blk.o
> > obj-$(CONFIG_X86_PMEM_LEGACY) += nd_e820.o
> > obj-$(CONFIG_OF_PMEM) += of_pmem.o
> > +obj-$(CONFIG_VIRTIO_PMEM) += virtio_pmem.o nd_virtio.o
> >
> > nd_pmem-y := pmem.o
> >
> > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
> > new file mode 100644
> > index 000000000000..ed7ddcc5a62c
> > --- /dev/null
> > +++ b/drivers/nvdimm/nd_virtio.c
> > @@ -0,0 +1,129 @@
> > +// 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 <linux/virtio_pmem.h>
> > +#include "nd.h"
> > +
> > + /* The interrupt handler */
> > +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);
> > + req_buf->wq_buf_avail = true;
> > + wake_up(&req_buf->wq_buf);
> > + list_del(&req_buf->list);
> > + }
> > + }
> > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > +}
> > +EXPORT_SYMBOL_GPL(host_ack);
> > +
> > + /* The request submission function */
> > +int virtio_pmem_flush(struct nd_region *nd_region)
> > +{
> > + int err, err1;
> > + unsigned long flags;
> > + struct scatterlist *sgs[2], sg, ret;
> > + struct virtio_device *vdev = nd_region->provider_data;
> > + struct virtio_pmem *vpmem = vdev->priv;
> > + struct virtio_pmem_request *req;
> > +
> > + might_sleep();
> > + req = kmalloc(sizeof(*req), GFP_KERNEL);
> > + if (!req)
> > + return -ENOMEM;
> > +
> > + req->done = false;
> > + strcpy(req->name, "FLUSH");
> > + init_waitqueue_head(&req->host_acked);
> > + init_waitqueue_head(&req->wq_buf);
> > + INIT_LIST_HEAD(&req->list);
> > + sg_init_one(&sg, req->name, strlen(req->name));
> > + sgs[0] = &sg;
> > + sg_init_one(&ret, &req->ret, sizeof(req->ret));
> > + sgs[1] = &ret;
> > +
> > + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > + /*
> > + * If virtqueue_add_sgs returns -ENOSPC then req_vq virtual
> > + * queue does not have free descriptor. We add the request
> > + * to req_list and wait for host_ack to wake us up when free
> > + * slots are available.
> > + */
> > + while ((err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req,
> > + GFP_ATOMIC)) == -ENOSPC) {
> > +
> > + dev_err(&vdev->dev, "failed to send command to virtio pmem"\
> > + "device, no free slots in the virtqueue\n");
> > + req->wq_buf_avail = false;
> > + list_add_tail(&req->list, &vpmem->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);
> > + }
> > + err1 = virtqueue_kick(vpmem->req_vq);
> > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > +
> > + /*
> > + * virtqueue_add_sgs failed with error different than -ENOSPC, we can't
> > + * do anything about that.
> > + */
> > + if (err || !err1) {
> > + dev_info(&vdev->dev, "failed to send command to virtio pmem device\n");
> > + err = -EIO;
> > + goto ret;
> > + }
> > +
> > + /* When host has read buffer, this completes via host_ack */
> > + wait_event(req->host_acked, req->done);
> > + err = req->ret;
> > +ret:
> > + kfree(req);
> > + return err;
> > +};
> > +
> > +/* The asynchronous flush callback function */
> > +int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
> > +{
> > + int rc = 0;
> > +
> > + /* Create child bio for asynchronous flush and chain with
> > + * parent bio. Otherwise directly call nd_region flush.
> > + */
> > + if (bio && bio->bi_iter.bi_sector != -1) {
> > + struct bio *child = bio_alloc(GFP_ATOMIC, 0);
> > +
> > + if (!child)
> > + return -ENOMEM;
> > + bio_copy_dev(child, bio);
> > + child->bi_opf = REQ_PREFLUSH;
> > + child->bi_iter.bi_sector = -1;
> > + bio_chain(child, bio);
> > + submit_bio(child);
> > + } else {
> > + if (virtio_pmem_flush(nd_region))
> > + rc = -EIO;
> > + }
> > +
> > + return rc;
> > +};
> > +EXPORT_SYMBOL_GPL(async_pmem_flush);
> > +MODULE_LICENSE("GPL");
> > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> > new file mode 100644
> > index 000000000000..cfc6381c4e5d
> > --- /dev/null
> > +++ b/drivers/nvdimm/virtio_pmem.c
> > @@ -0,0 +1,117 @@
> > +// 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 <linux/virtio_pmem.h>
> > +#include "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)
> > +{
> > + /* single vq */
> > + vpmem->req_vq = virtio_find_single_vq(vpmem->vdev,
> > + host_ack, "flush_queue");
> > + if (IS_ERR(vpmem->req_vq))
> > + return PTR_ERR(vpmem->req_vq);
> > +
> > + 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 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 access disabled\n",
> > + __func__);
> > + return -EINVAL;
> > + }
> > +
> > + vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem), GFP_KERNEL);
> > + if (!vpmem) {
> > + err = -ENOMEM;
> > + goto out_err;
> > + }
> > +
> > + vpmem->vdev = vdev;
> > + vdev->priv = vpmem;
> > + 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_register(&vdev->dev,
> > + &vpmem->nd_desc);
> > + if (!vpmem->nvdimm_bus)
> > + goto out_vq;
> > +
> > + dev_set_drvdata(&vdev->dev, vpmem->nvdimm_bus);
> > +
> > + ndr_desc.res = &res;
> > + ndr_desc.numa_node = nid;
> > + ndr_desc.flush = async_pmem_flush;
> > + set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
> > + set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
> > + nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
> > +
> > + if (!nd_region)
> > + goto out_nd;
> > + nd_region->provider_data = dev_to_virtio(nd_region->dev.parent->parent);
> > + return 0;
> > +out_nd:
> > + err = -ENXIO;
> > + nvdimm_bus_unregister(vpmem->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 nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
> > +
> > + nvdimm_bus_unregister(nvdimm_bus);
> > + vdev->config->del_vqs(vdev);
> > + vdev->config->reset(vdev);
> > +}
> > +
> > +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");
> > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> > index 35897649c24f..9f634a2ed638 100644
> > --- a/drivers/virtio/Kconfig
> > +++ b/drivers/virtio/Kconfig
> > @@ -42,6 +42,16 @@ config VIRTIO_PCI_LEGACY
> >
> > If unsure, say Y.
> >
> > +config VIRTIO_PMEM
> > + tristate "Support for virtio pmem driver"
> > + depends on VIRTIO
> > + depends on LIBNVDIMM
> > + 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/include/linux/virtio_pmem.h b/include/linux/virtio_pmem.h
> > new file mode 100644
> > index 000000000000..ab1da877575d
> > --- /dev/null
> > +++ b/include/linux/virtio_pmem.h
> > @@ -0,0 +1,60 @@
> > +/* 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 <linux/virtio_ids.h>
> > +#include <linux/module.h>
> > +#include <linux/virtio_config.h>
> > +#include <uapi/linux/virtio_pmem.h>
> > +#include <linux/libnvdimm.h>
> > +#include <linux/spinlock.h>
> > +
> > +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;
> > + 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;
> > +};
> > +
> > +void host_ack(struct virtqueue *vq);
> > +int async_pmem_flush(struct nd_region *nd_region, struct bio *bio);
> > +#endif
> > diff --git a/include/uapi/linux/virtio_ids.h
> > b/include/uapi/linux/virtio_ids.h
> > index 6d5c3b2d4f4d..32b2f94d1f58 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 27 /* 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 000000000000..fa3f7d52717a
> > --- /dev/null
> > +++ b/include/uapi/linux/virtio_pmem.h
> > @@ -0,0 +1,10 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +#ifndef _UAPI_LINUX_VIRTIO_PMEM_H
> > +#define _UAPI_LINUX_VIRTIO_PMEM_H
> > +
> > +struct virtio_pmem_config {
> > + __le64 start;
> > + __le64 size;
> > +};
> > +#endif
> > --
> > 2.20.1
>
>
