Re: [Qemu-devel] [PATCH v3 2/5] virtio-pmem: Add virtio pmem driver

[Michael S. Tsirkin]

On Wed, Jan 09, 2019 at 08:17:33PM +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 <address@hidden>
> ---
>  drivers/nvdimm/virtio_pmem.c     |  84 ++++++++++++++++++++++++++
>  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 ++++

As with any uapi change, you need to CC the virtio dev
mailing list (subscribers only, sorry about that).


>  7 files changed, 290 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/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> new file mode 100644
> index 0000000..2a1b1ba
> --- /dev/null
> +++ b/drivers/nvdimm/virtio_pmem.c
> @@ -0,0 +1,84 @@
> +// 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);
> +                     list_del(&vpmem->req_list);
> +                     req_buf->wq_buf_avail = true;
> +                     wake_up(&req_buf->wq_buf);
> +             }
> +     }
> +     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;
> +     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 = req->wq_buf_avail = false;
> +     strcpy(req->name, "FLUSH");
> +     init_waitqueue_head(&req->host_acked);
> +     init_waitqueue_head(&req->wq_buf);
> +     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);
> +     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);
> +     err = req->ret;
> +     kfree(req);
> +
> +     return err;
> +};
> +EXPORT_SYMBOL_GPL(virtio_pmem_flush);
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 3589764..9f634a2 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/drivers/virtio/Makefile b/drivers/virtio/Makefile
> index 3a2b5c5..143ce91 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) += pmem.o ../nvdimm/virtio_pmem.o
> diff --git a/drivers/virtio/pmem.c b/drivers/virtio/pmem.c
> new file mode 100644
> index 0000000..51f5349
> --- /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 <linux/virtio_pmem.h>
> +#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)
> +{
> +     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;
> +};
> +
> +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);
> +     nd_region->provider_data =  dev_to_virtio
> +                                     (nd_region->dev.parent->parent);
> +
> +     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);
> +}
> +
> +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/include/linux/virtio_pmem.h b/include/linux/virtio_pmem.h
> new file mode 100644
> index 0000000..224f9d9
> --- /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 virtio_pmem_flush(struct nd_region *nd_region);
> +#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..fa3f7d5
> --- /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
> -- 
> 2.9.3