Date:   Mon, 23 Sep 2019 22:28:30 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Jason Wang <jasowang@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
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CC:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
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Subject: RE: [PATCH 4/6] virtio: introduce a mdev based transport



> -----Original Message-----
> From: Jason Wang <jasowang@...hat.com>
> Sent: Monday, September 23, 2019 8:03 AM
> To: kvm@...r.kernel.org; linux-s390@...r.kernel.org; linux-
> kernel@...r.kernel.org; dri-devel@...ts.freedesktop.org; intel-
> gfx@...ts.freedesktop.org; intel-gvt-dev@...ts.freedesktop.org;
> kwankhede@...dia.com; alex.williamson@...hat.com; mst@...hat.com;
> tiwei.bie@...el.com
> Cc: virtualization@...ts.linux-foundation.org; netdev@...r.kernel.org;
> cohuck@...hat.com; maxime.coquelin@...hat.com;
> cunming.liang@...el.com; zhihong.wang@...el.com;
> rob.miller@...adcom.com; xiao.w.wang@...el.com;
> haotian.wang@...ive.com; zhenyuw@...ux.intel.com; zhi.a.wang@...el.com;
> jani.nikula@...ux.intel.com; joonas.lahtinen@...ux.intel.com;
> rodrigo.vivi@...el.com; airlied@...ux.ie; daniel@...ll.ch;
> farman@...ux.ibm.com; pasic@...ux.ibm.com; sebott@...ux.ibm.com;
> oberpar@...ux.ibm.com; heiko.carstens@...ibm.com; gor@...ux.ibm.com;
> borntraeger@...ibm.com; akrowiak@...ux.ibm.com; freude@...ux.ibm.com;
> lingshan.zhu@...el.com; Ido Shamay <idos@...lanox.com>;
> eperezma@...hat.com; lulu@...hat.com; Parav Pandit
> <parav@...lanox.com>; Jason Wang <jasowang@...hat.com>
> Subject: [PATCH 4/6] virtio: introduce a mdev based transport
> 
> 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 device specific opswhich is a part of
> mdev_parent_ops now.
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  MAINTAINERS                     |   1 +
>  drivers/vfio/mdev/Kconfig       |   7 +
>  drivers/vfio/mdev/Makefile      |   1 +
>  drivers/vfio/mdev/virtio_mdev.c | 416 ++++++++++++++++++++++++++++++++
>  4 files changed, 425 insertions(+)
>  create mode 100644 drivers/vfio/mdev/virtio_mdev.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 89832b316500..820ec250cc52 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17202,6 +17202,7 @@ F:	include/linux/virtio*.h
>  F:	include/uapi/linux/virtio_*.h
>  F:	drivers/crypto/virtio/
>  F:	mm/balloon_compaction.c
> +F:	drivers/vfio/mdev/virtio_mdev.c
> 
>  VIRTIO BLOCK AND SCSI DRIVERS
>  M:	"Michael S. Tsirkin" <mst@...hat.com>
> diff --git a/drivers/vfio/mdev/Kconfig b/drivers/vfio/mdev/Kconfig index
> 5da27f2100f9..c488c31fc137 100644
> --- a/drivers/vfio/mdev/Kconfig
> +++ b/drivers/vfio/mdev/Kconfig
> @@ -16,3 +16,10 @@ config VFIO_MDEV_DEVICE
>  	default n
>  	help
>  	  VFIO based driver for Mediated devices.
> +
> +config VIRTIO_MDEV_DEVICE
> +	tristate "VIRTIO driver for Mediated devices"
> +	depends on VFIO_MDEV && VIRTIO
> +	default n
> +	help
> +	  VIRTIO based driver for Mediated devices.
> diff --git a/drivers/vfio/mdev/Makefile b/drivers/vfio/mdev/Makefile index
> 101516fdf375..99d31e29c23e 100644
> --- a/drivers/vfio/mdev/Makefile
> +++ b/drivers/vfio/mdev/Makefile
> @@ -4,3 +4,4 @@ mdev-y := mdev_core.o mdev_sysfs.o mdev_driver.o
> 
>  obj-$(CONFIG_VFIO_MDEV) += mdev.o
>  obj-$(CONFIG_VFIO_MDEV_DEVICE) += vfio_mdev.o
> +obj-$(CONFIG_VIRTIO_MDEV_DEVICE) += virtio_mdev.o
> diff --git a/drivers/vfio/mdev/virtio_mdev.c b/drivers/vfio/mdev/virtio_mdev.c
> new file mode 100644 index 000000000000..919a082adc9c
> --- /dev/null
> +++ b/drivers/vfio/mdev/virtio_mdev.c
> @@ -0,0 +1,416 @@
> +// 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@...hat.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/mdev.h>
> +#include <linux/virtio_mdev.h>
> +#include <linux/virtio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ring.h>
> +#include "mdev_private.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;
> +	unsigned long version;
> +
> +	struct virtqueue **vqs;
Every lock must need a comment to describe what it locks.
I don't see this lock is used in this patch. Please introduce in the patch that uses it.
> +	spinlock_t lock;
> +};
> +
> +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 const struct virtio_mdev_parent_ops *mdev_get_parent_ops(struct
> +mdev_device *mdev) {
> +	struct mdev_parent *parent = mdev->parent;
> +
> +	return parent->ops->device_ops;
> +}
> +
> +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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +	return ops->get_generation(mdev);
> +}
> +
> +static u8 virtio_mdev_get_status(struct virtio_device *vdev) {
> +	struct mdev_device *mdev = vm_get_mdev(vdev);
> +	const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 index,
> +		     void (*callback)(struct virtqueue *vq),
> +		     const char *name, bool ctx)
> +{
> +	struct mdev_device *mdev = vm_get_mdev(vdev);
> +	const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +	struct virtio_mdev_vq_info *info;
> +	struct virtio_mdev_callback cb;
> +	struct virtqueue *vq;
> +	u32 align, num;
> +	u64 desc_addr, driver_addr, device_addr;
> +	int err;
> +
> +	if (!name)
> +		return NULL;
> +
> +	/* Queue shouldn't already be set up. */
> +	if (ops->get_vq_ready(mdev, index)) {
> +		err = -ENOENT;
> +		goto error_available;
> +	}
> +
No need for a goto, to single return done later.
Just do 
	if (ops->get_vq_ready(mdev, index))
		return -ENOENT;

> +	/* Allocate and fill out our active queue description */
> +	info = kmalloc(sizeof(*info), GFP_KERNEL);
> +	if (!info) {
> +		err = -ENOMEM;
> +		goto error_kmalloc;
> +	}
> +
Similar to above one.

> +	num = ops->get_queue_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;
> +
> +	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);
> +error_kmalloc:
> +error_available:
> +	return ERR_PTR(err);
> +
> +}
> +
> +static void virtio_mdev_del_vq(struct virtqueue *vq) {
> +	struct mdev_device *mdev = vm_get_mdev(vq->vdev);
> +	const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +	struct virtio_mdev_vq_info *info = vq->priv;
> +	unsigned int index = vq->index;
> +
> +	/* 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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +	struct virtio_mdev_callback cb;
> +	int i, err, queue_idx = 0;
> +
> +	vm_dev->vqs = kmalloc_array(queue_idx, sizeof(*vm_dev->vqs),
> +				    GFP_KERNEL);
> +	if (!vm_dev->vqs)
> +		return -ENOMEM;
> +
> +	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:
> +	kfree(vm_dev->vqs);
> +	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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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 virtio_mdev_parent_ops *ops =
> mdev_get_parent_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);
> +}
> +
> +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);
> +
> +	devm_kfree(_d, vm_dev);
> +}
> +
> +static int virtio_mdev_probe(struct device *dev) {
> +	struct mdev_device *mdev = to_mdev_device(dev);
> +	const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_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;
> +	vm_dev->vqs = NULL;
> +	spin_lock_init(&vm_dev->lock);
> +
> +	vm_dev->version = ops->get_version(mdev);
> +	if (vm_dev->version != 1) {
> +		dev_err(dev, "Version %ld not supported!\n",
> +			vm_dev->version);
> +		return -ENXIO;
> +	}
> +
> +	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);
> +
> +	dev_set_drvdata(dev, vm_dev);
No need to set drvdata when there is error returned from register_virtio_device().

> +
> +	return rc;
> +
Extra line not needed.
> +}
> +
> +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 struct mdev_class_id id_table[] = {
> +	{ MDEV_ID_VIRTIO },
> +	{ 0 },
> +};
> +
> +static struct mdev_driver virtio_mdev_driver = {
> +	.name	= "virtio_mdev",
> +	.probe	= virtio_mdev_probe,
> +	.remove	= virtio_mdev_remove,
No need for tab, just do single white space.

> +	.id_table = id_table,
> +};
> +
> +static int __init virtio_mdev_init(void) {
> +	return mdev_register_driver(&virtio_mdev_driver, THIS_MODULE); }
> +
> +static void __exit virtio_mdev_exit(void) {
> +	mdev_unregister_driver(&virtio_mdev_driver);
> +}
> +
> +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);
> --
> 2.19.1

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