Re: [PATCH V12 5/6] virtio: introduce a mdev based transport

Michael S. Tsirkin
2019-11-18T10:44:46Z

On Mon, Nov 18, 2019 at 02:17:02PM +0800, Jason Wang wrote:
> This patch introduces a new mdev transport for virtio. This is used to
> use kernel virtio driver to drive the mediated device that is capable
> of populating virtqueue directly.
>
> A new virtio-mdev driver will be registered to the mdev bus, when a
> new virtio-mdev device is probed, it will register the device with
> mdev based config ops. This means it is a software transport between
> mdev driver and mdev device. The transport was implemented through
> bus_ops of mdev parent.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/virtio/Kconfig | 13 ++
> drivers/virtio/Makefile | 1 +
> drivers/virtio/virtio_mdev.c | 409 +++++++++++++++++++++++++++++++++++
> include/linux/mdev_virtio.h | 5 +
> 4 files changed, 428 insertions(+)
> create mode 100644 drivers/virtio/virtio_mdev.c
>
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 078615cf2afc..6a89b3de97d3 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -43,6 +43,19 @@ config VIRTIO_PCI_LEGACY
>
> If unsure, say Y.
>
> +config VIRTIO_MDEV
> + tristate "MDEV driver for virtio devices"
> + depends on MDEV_VIRTIO
> + default n
> + help
> + This driver provides support for virtio based paravirtual
> + device driver over MDEV bus. For this to be useful, you need
> + an appropriate virtio mdev device implementation that
> + operates on a physical device to allow the datapath of virtio
> + to be offloaded to hardware.
> +
> + If unsure, say M.
> +
> config VIRTIO_PMEM
> tristate "Support for virtio pmem driver"
> depends on VIRTIO
> diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
> index 3a2b5c5dcf46..f2997b6c812f 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_MDEV) += virtio_mdev.o
> diff --git a/drivers/virtio/virtio_mdev.c b/drivers/virtio/virtio_mdev.c
> new file mode 100644
> index 000000000000..7fdb42f055df
> --- /dev/null
> +++ b/drivers/virtio/virtio_mdev.c
> @@ -0,0 +1,409 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * VIRTIO based driver for Mediated device
> + *
> + * Copyright (c) 2019, Red Hat. All rights reserved.
> + * Author: Jason Wang <jasowang@redhat.com>
> + *
> + */
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/uuid.h>
> +#include <linux/virtio.h>
> +#include <linux/mdev_virtio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ring.h>
> +
> +#define DRIVER_VERSION "0.1"
> +#define DRIVER_AUTHOR "Red Hat Corporation"
> +#define DRIVER_DESC "VIRTIO based driver for Mediated device"
> +
> +#define to_virtio_mdev_device(dev) \
> + container_of(dev, struct virtio_mdev_device, vdev)
> +
> +struct virtio_mdev_device {
> + struct virtio_device vdev;
> + struct mdev_device *mdev;
> + u64 features;
> +
> + /* The lock to protect virtqueue list */
> + spinlock_t lock;
> + /* List of virtio_mdev_vq_info */
> + struct list_head virtqueues;
> +};
> +
> +struct virtio_mdev_vq_info {
> + /* the actual virtqueue */
> + struct virtqueue *vq;
> +
> + /* the list node for the virtqueues list */
> + struct list_head node;
> +};
> +
> +static struct mdev_device *vm_get_mdev(struct virtio_device *vdev)
> +{
> + struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> + struct mdev_device *mdev = vm_dev->mdev;
> +
> + return mdev;
> +}
> +
> +static void virtio_mdev_get(struct virtio_device *vdev, unsigned offset,
> + void *buf, unsigned len)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + ops->get_config(mdev, offset, buf, len);
> +}
> +
> +static void virtio_mdev_set(struct virtio_device *vdev, unsigned offset,
> + const void *buf, unsigned len)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + ops->set_config(mdev, offset, buf, len);
> +}
> +
> +static u32 virtio_mdev_generation(struct virtio_device *vdev)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> +
> + if (ops->get_generation)
> + return ops->get_generation(mdev);
> +
> + return 0;
> +}
> +
> +static u8 virtio_mdev_get_status(struct virtio_device *vdev)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + return ops->get_status(mdev);
> +}
> +
> +static void virtio_mdev_set_status(struct virtio_device *vdev, u8 status)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + return ops->set_status(mdev, status);
> +}
> +
> +static void virtio_mdev_reset(struct virtio_device *vdev)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + return ops->set_status(mdev, 0);
> +}
> +
> +static bool virtio_mdev_notify(struct virtqueue *vq)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vq->vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + ops->kick_vq(mdev, vq->index);
> +
> + return true;
> +}
> +
> +static irqreturn_t virtio_mdev_config_cb(void *private)
> +{
> + struct virtio_mdev_device *vm_dev = private;
> +
> + virtio_config_changed(&vm_dev->vdev);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t virtio_mdev_virtqueue_cb(void *private)
> +{
> + struct virtio_mdev_vq_info *info = private;
> +
> + return vring_interrupt(0, info->vq);
> +}
> +
> +static struct virtqueue *
> +virtio_mdev_setup_vq(struct virtio_device *vdev, unsigned int index,
> + void (*callback)(struct virtqueue *vq),
> + const char *name, bool ctx)
> +{
> + struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> + struct virtio_mdev_vq_info *info;
> + struct virtio_mdev_callback cb;
> + struct virtqueue *vq;
> + u64 desc_addr, driver_addr, device_addr;
> + unsigned long flags;
> + u32 align, num;
> + int err;
> +
> + if (!name)
> + return NULL;
> +
> + /* Queue shouldn't already be set up. */
> + if (ops->get_vq_ready(mdev, index))
> + return ERR_PTR(-ENOENT);
> +
> + /* Allocate and fill out our active queue description */
> + info = kmalloc(sizeof(*info), GFP_KERNEL);
> + if (!info)
> + return ERR_PTR(-ENOMEM);
> +
> + num = ops->get_vq_num_max(mdev);
> + if (num == 0) {
> + err = -ENOENT;
> + goto error_new_virtqueue;
> + }
> +
> + /* Create the vring */
> + align = ops->get_vq_align(mdev);
> + vq = vring_create_virtqueue(index, num, align, vdev,
> + true, true, ctx,
> + virtio_mdev_notify, callback, name);
> + if (!vq) {
> + err = -ENOMEM;
> + goto error_new_virtqueue;
> + }
> +
> + /* Setup virtqueue callback */
> + cb.callback = virtio_mdev_virtqueue_cb;
> + cb.private = info;
> + ops->set_vq_cb(mdev, index, &cb);
> + ops->set_vq_num(mdev, index, virtqueue_get_vring_size(vq));
> +
> + desc_addr = virtqueue_get_desc_addr(vq);
> + driver_addr = virtqueue_get_avail_addr(vq);
> + device_addr = virtqueue_get_used_addr(vq);
> +
> + if (ops->set_vq_address(mdev, index,
> + desc_addr, driver_addr,
> + device_addr)) {
> + err = -EINVAL;
> + goto err_vq;
> + }
> +
> + ops->set_vq_ready(mdev, index, 1);
> +
> + vq->priv = info;
> + info->vq = vq;
> +
> + spin_lock_irqsave(&vm_dev->lock, flags);
> + list_add(&info->node, &vm_dev->virtqueues);
> + spin_unlock_irqrestore(&vm_dev->lock, flags);
> +
> + return vq;
> +
> +err_vq:
> + vring_del_virtqueue(vq);
> +error_new_virtqueue:
> + ops->set_vq_ready(mdev, index, 0);
> + WARN_ON(ops->get_vq_ready(mdev, index));
> + kfree(info);
> + return ERR_PTR(err);
> +}
> +
> +static void virtio_mdev_del_vq(struct virtqueue *vq)
> +{
> + struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vq->vdev);
> + struct mdev_device *mdev = vm_dev->mdev;
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> + struct virtio_mdev_vq_info *info = vq->priv;
> + unsigned int index = vq->index;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&vm_dev->lock, flags);
> + list_del(&info->node);
> + spin_unlock_irqrestore(&vm_dev->lock, flags);
> +
> + /* Select and deactivate the queue */
> + ops->set_vq_ready(mdev, index, 0);
> + WARN_ON(ops->get_vq_ready(mdev, index));
> +
> + vring_del_virtqueue(vq);
> +
> + kfree(info);
> +}
> +
> +static void virtio_mdev_del_vqs(struct virtio_device *vdev)
> +{
> + struct virtqueue *vq, *n;
> +
> + list_for_each_entry_safe(vq, n, &vdev->vqs, list)
> + virtio_mdev_del_vq(vq);
> +}
> +
> +static int virtio_mdev_find_vqs(struct virtio_device *vdev, unsigned nvqs,
> + struct virtqueue *vqs[],
> + vq_callback_t *callbacks[],
> + const char * const names[],
> + const bool *ctx,
> + struct irq_affinity *desc)
> +{
> + struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> + struct virtio_mdev_callback cb;
> + int i, err, queue_idx = 0;
> +
> + for (i = 0; i < nvqs; ++i) {
> + if (!names[i]) {
> + vqs[i] = NULL;
> + continue;
> + }
> +
> + vqs[i] = virtio_mdev_setup_vq(vdev, queue_idx++,
> + callbacks[i], names[i], ctx ?
> + ctx[i] : false);
> + if (IS_ERR(vqs[i])) {
> + err = PTR_ERR(vqs[i]);
> + goto err_setup_vq;
> + }
> + }
> +
> + cb.callback = virtio_mdev_config_cb;
> + cb.private = vm_dev;
> + ops->set_config_cb(mdev, &cb);
> +
> + return 0;
> +
> +err_setup_vq:
> + virtio_mdev_del_vqs(vdev);
> + return err;
> +}
> +
> +static u64 virtio_mdev_get_features(struct virtio_device *vdev)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + return ops->get_features(mdev);
> +}
> +
> +static int virtio_mdev_finalize_features(struct virtio_device *vdev)
> +{
> + struct mdev_device *mdev = vm_get_mdev(vdev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> +
> + /* Give virtio_ring a chance to accept features. */
> + vring_transport_features(vdev);
> +
> + return ops->set_features(mdev, vdev->features);
> +}
> +
> +static const char *virtio_mdev_bus_name(struct virtio_device *vdev)
> +{
> + struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> + struct mdev_device *mdev = vm_dev->mdev;
> +
> + return dev_name(mdev_dev(mdev));
> +}
> +
> +static const struct virtio_config_ops virtio_mdev_config_ops = {
> + .get = virtio_mdev_get,
> + .set = virtio_mdev_set,
> + .generation = virtio_mdev_generation,
> + .get_status = virtio_mdev_get_status,
> + .set_status = virtio_mdev_set_status,
> + .reset = virtio_mdev_reset,
> + .find_vqs = virtio_mdev_find_vqs,
> + .del_vqs = virtio_mdev_del_vqs,
> + .get_features = virtio_mdev_get_features,
> + .finalize_features = virtio_mdev_finalize_features,
> + .bus_name = virtio_mdev_bus_name,
> +};
> +
> +static void virtio_mdev_release_dev(struct device *_d)
> +{
> + struct virtio_device *vdev =
> + container_of(_d, struct virtio_device, dev);
> + struct virtio_mdev_device *vm_dev =
> + container_of(vdev, struct virtio_mdev_device, vdev);
> + struct mdev_device *mdev = vm_dev->mdev;
> +
> + devm_kfree(mdev_dev(mdev), vm_dev);
> +}
> +
> +static int virtio_mdev_probe(struct device *dev)
> +{
> + struct mdev_device *mdev = mdev_virtio_from_dev(dev);
> + const struct mdev_virtio_ops *ops = mdev_virtio_get_ops(mdev);
> + struct virtio_mdev_device *vm_dev;
> + int rc;
> +
> + vm_dev = devm_kzalloc(dev, sizeof(*vm_dev), GFP_KERNEL);
> + if (!vm_dev)
> + return -ENOMEM;
> +
> + vm_dev->vdev.dev.parent = dev;
> + vm_dev->vdev.dev.release = virtio_mdev_release_dev;
> + vm_dev->vdev.config = &virtio_mdev_config_ops;
> + vm_dev->mdev = mdev;
> + INIT_LIST_HEAD(&vm_dev->virtqueues);
> + spin_lock_init(&vm_dev->lock);
> +
> + vm_dev->vdev.id.device = ops->get_device_id(mdev);
> + if (vm_dev->vdev.id.device == 0)
> + return -ENODEV;
> +
> + vm_dev->vdev.id.vendor = ops->get_vendor_id(mdev);
> + rc = register_virtio_device(&vm_dev->vdev);
> + if (rc)
> + put_device(dev);
> + else
> + dev_set_drvdata(dev, vm_dev);
> +
> + return rc;
> +}
> +
> +static void virtio_mdev_remove(struct device *dev)
> +{
> + struct virtio_mdev_device *vm_dev = dev_get_drvdata(dev);
> +
> + unregister_virtio_device(&vm_dev->vdev);
> +}
> +
> +static const struct mdev_virtio_class_id virtio_id_table[] = {
> + { MDEV_VIRTIO_CLASS_ID_VIRTIO },
> + { 0 },
> +};
> +

Do we still need the class ID? It's a virtio mdev bus,
do we need a virtio class as well?

> +MODULE_DEVICE_TABLE(mdev_virtio, virtio_id_table);
> +
> +static struct mdev_virtio_driver virtio_mdev_driver = {
> + .drv = {
> + .name = "virtio_mdev",
> + .probe = virtio_mdev_probe,
> + .remove = virtio_mdev_remove,
> + },
> + .id_table = virtio_id_table,
> +};
> +
> +static int __init virtio_mdev_init(void)
> +{
> + return mdev_register_driver(&virtio_mdev_driver.drv, THIS_MODULE,
> + &mdev_virtio_bus_type);
> +}
> +
> +static void __exit virtio_mdev_exit(void)
> +{
> + mdev_unregister_driver(&virtio_mdev_driver.drv);
> +}
> +
> +module_init(virtio_mdev_init)
> +module_exit(virtio_mdev_exit)
> +
> +MODULE_VERSION(DRIVER_VERSION);
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR(DRIVER_AUTHOR);
> +MODULE_DESCRIPTION(DRIVER_DESC);
> diff --git a/include/linux/mdev_virtio.h b/include/linux/mdev_virtio.h
> index ef2dbb6c383a..5f75f3cf59e1 100644
> --- a/include/linux/mdev_virtio.h
> +++ b/include/linux/mdev_virtio.h
> @@ -25,6 +25,11 @@ struct virtio_mdev_callback {
> void *private;
> };
>
> +enum {
> + MDEV_VIRTIO_CLASS_ID_VIRTIO = 1,
> + /* New entries must be added here */
> +};
> +
> /**
> * struct mdev_virtio_device_ops - Structure to be registered for each
> * mdev device to register the device for virtio/vhost drivers.
> --
> 2.19.1