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Subject: Re: [PATCH v3] vhost: introduce mdev based hardware backend
To:     Tiwei Bie <tiwei.bie@intel.com>
Cc:     mst@redhat.com, alex.williamson@redhat.com,
        maxime.coquelin@redhat.com, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, dan.daly@intel.com,
        cunming.liang@intel.com, zhihong.wang@intel.com,
        lingshan.zhu@intel.com
References: <20191029100734.9861-1-tiwei.bie@intel.com>
 <e653058c-d480-2195-8915-7bf7378ac76e@redhat.com> <20191030055228.GA9578@___>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <1a7a10c7-0772-8fce-fb18-78c2dcf15fbc@redhat.com>
Date:   Wed, 30 Oct 2019 15:07:12 +0800
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On 2019/10/30 =E4=B8=8B=E5=8D=881:52, Tiwei Bie wrote:
> On Wed, Oct 30, 2019 at 09:55:57AM +0800, Jason Wang wrote:
>> On 2019/10/29 =E4=B8=8B=E5=8D=886:07, Tiwei Bie wrote:
>>> This patch introduces a mdev based hardware vhost backend.
>>> This backend is built on top of the same abstraction used
>>> in virtio-mdev and provides a generic vhost interface for
>>> userspace to accelerate the virtio devices in guest.
>>>
>>> This backend is implemented as a mdev device driver on top
>>> of the same mdev device ops used in virtio-mdev but using
>>> a different mdev class id, and it will register the device
>>> as a VFIO device for userspace to use. Userspace can setup
>>> the IOMMU with the existing VFIO container/group APIs and
>>> then get the device fd with the device name. After getting
>>> the device fd of this device, userspace can use vhost ioctls
>>> to setup the backend.
>>
>> Hi Tiwei:
>>
>> The patch looks good overall, just few comments & nits.
> Thanks for the review! I do appreciate it.


You're welcome :)


>
>>
>>> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
>>> ---
>>> This patch depends on below series:
>>> https://lkml.org/lkml/2019/10/23/614
>>>
>>> v2 -> v3:
>>> - Fix the return value (Jason);
>>> - Don't cache unnecessary information in vhost-mdev (Jason);
>>> - Get rid of the memset in open (Jason);
>>> - Add comments for VHOST_SET_MEM_TABLE, ... (Jason);
>>> - Filter out unsupported features in vhost-mdev (Jason);
>>> - Add _GET_DEVICE_ID ioctl (Jason);
>>> - Add _GET_CONFIG/_SET_CONFIG ioctls (Jason);
>>> - Drop _GET_QUEUE_NUM ioctl (Jason);
>>> - Fix the copy-paste errors in _IOW/_IOR usage;
>>> - Some minor fixes and improvements;
>>>
>>> v1 -> v2:
>>> - Replace _SET_STATE with _SET_STATUS (MST);
>>> - Check status bits at each step (MST);
>>> - Report the max ring size and max number of queues (MST);
>>> - Add missing MODULE_DEVICE_TABLE (Jason);
>>> - Only support the network backend w/o multiqueue for now;
>>> - Some minor fixes and improvements;
>>> - Rebase on top of virtio-mdev series v4;
>>>
>>> RFC v4 -> v1:
>>> - Implement vhost-mdev as a mdev device driver directly and
>>>   connect it to VFIO container/group. (Jason);
>>> - Pass ring addresses as GPAs/IOVAs in vhost-mdev to avoid
>>>   meaningless HVA->GPA translations (Jason);
>>>
>>> RFC v3 -> RFC v4:
>>> - Build vhost-mdev on top of the same abstraction used by
>>>   virtio-mdev (Jason);
>>> - Introduce vhost fd and pass VFIO fd via SET_BACKEND ioctl (MST);
>>>
>>> RFC v2 -> RFC v3:
>>> - Reuse vhost's ioctls instead of inventing a VFIO regions/irqs
>>>   based vhost protocol on top of vfio-mdev (Jason);
>>>
>>> RFC v1 -> RFC v2:
>>> - Introduce a new VFIO device type to build a vhost protocol
>>>   on top of vfio-mdev;
>>>
>>>  drivers/vfio/mdev/mdev_core.c    |  20 ++
>>>  drivers/vfio/mdev/mdev_private.h |   1 +
>>>  drivers/vhost/Kconfig            |  12 +
>>>  drivers/vhost/Makefile           |   3 +
>>>  drivers/vhost/mdev.c             | 554 +++++++++++++++++++++++++++++++
>>>  include/linux/mdev.h             |   5 +
>>>  include/uapi/linux/vhost.h       |  18 +
>>>  include/uapi/linux/vhost_types.h |   8 +
>>>  8 files changed, 621 insertions(+)
>>>  create mode 100644 drivers/vhost/mdev.c
>>>
>>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_cor=
e.c
>>> index 9b00c3513120..3cfd787d605c 100644
>>> --- a/drivers/vfio/mdev/mdev_core.c
>>> +++ b/drivers/vfio/mdev/mdev_core.c
>>> @@ -96,6 +96,26 @@ mdev_get_virtio_ops(struct mdev_device *mdev)
>>>  }
>>>  EXPORT_SYMBOL(mdev_get_virtio_ops);
>>> =20
>>> +/* Specify the vhost device ops for the mdev device, this
>>> + * must be called during create() callback for vhost mdev device.
>>> + */
>>> +void mdev_set_vhost_ops(struct mdev_device *mdev,
>>> +=09=09=09const struct virtio_mdev_device_ops *vhost_ops)
>>> +{
>>> +=09mdev_set_class(mdev, MDEV_CLASS_ID_VHOST);
>>> +=09mdev->vhost_ops =3D vhost_ops;
>>> +}
>>> +EXPORT_SYMBOL(mdev_set_vhost_ops);
>>> +
>>> +/* Get the vhost device ops for the mdev device. */
>>> +const struct virtio_mdev_device_ops *
>>> +mdev_get_vhost_ops(struct mdev_device *mdev)
>>> +{
>>> +=09WARN_ON(mdev->class_id !=3D MDEV_CLASS_ID_VHOST);
>>> +=09return mdev->vhost_ops;
>>> +}
>>> +EXPORT_SYMBOL(mdev_get_vhost_ops);
>>> +
>>>  struct device *mdev_dev(struct mdev_device *mdev)
>>>  {
>>>  =09return &mdev->dev;
>>> diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_=
private.h
>>> index 7b47890c34e7..5597c846e52f 100644
>>> --- a/drivers/vfio/mdev/mdev_private.h
>>> +++ b/drivers/vfio/mdev/mdev_private.h
>>> @@ -40,6 +40,7 @@ struct mdev_device {
>>>  =09union {
>>>  =09=09const struct vfio_mdev_device_ops *vfio_ops;
>>>  =09=09const struct virtio_mdev_device_ops *virtio_ops;
>>> +=09=09const struct virtio_mdev_device_ops *vhost_ops;
>>>  =09};
>>>  };
>>> =20
>>> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
>>> index 3d03ccbd1adc..062cada28f89 100644
>>> --- a/drivers/vhost/Kconfig
>>> +++ b/drivers/vhost/Kconfig
>>> @@ -34,6 +34,18 @@ config VHOST_VSOCK
>>>  =09To compile this driver as a module, choose M here: the module will =
be called
>>>  =09vhost_vsock.
>>> =20
>>> +config VHOST_MDEV
>>> +=09tristate "Vhost driver for Mediated devices"
>>> +=09depends on EVENTFD && VFIO && VFIO_MDEV
>>> +=09select VHOST
>>> +=09default n
>>> +=09---help---
>>> +=09This kernel module can be loaded in host kernel to accelerate
>>> +=09guest virtio devices with the mediated device based backends.
>>> +
>>> +=09To compile this driver as a module, choose M here: the module will
>>> +=09be called vhost_mdev.
>>> +
>>>  config VHOST
>>>  =09tristate
>>>  =09---help---
>>> diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
>>> index 6c6df24f770c..ad9c0f8c6d8c 100644
>>> --- a/drivers/vhost/Makefile
>>> +++ b/drivers/vhost/Makefile
>>> @@ -10,4 +10,7 @@ vhost_vsock-y :=3D vsock.o
>>> =20
>>>  obj-$(CONFIG_VHOST_RING) +=3D vringh.o
>>> =20
>>> +obj-$(CONFIG_VHOST_MDEV) +=3D vhost_mdev.o
>>> +vhost_mdev-y :=3D mdev.o
>>> +
>>>  obj-$(CONFIG_VHOST)=09+=3D vhost.o
>>> diff --git a/drivers/vhost/mdev.c b/drivers/vhost/mdev.c
>>> new file mode 100644
>>> index 000000000000..35b2fb33e686
>>> --- /dev/null
>>> +++ b/drivers/vhost/mdev.c
>>> @@ -0,0 +1,554 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Vhost driver for mediated device based backends.
>>> + *
>>> + * Copyright (C) 2018-2019 Intel Corporation.
>>> + *
>>> + * Author: Tiwei Bie <tiwei.bie@intel.com>
>>> + *
>>> + * Thanks to Jason Wang and Michael S. Tsirkin for the valuable
>>> + * comments and suggestions.  And thanks to Cunming Liang and
>>> + * Zhihong Wang for all their supports.
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/module.h>
>>> +#include <linux/mdev.h>
>>> +#include <linux/vfio.h>
>>> +#include <linux/vhost.h>
>>> +#include <linux/virtio_net.h>
>>> +#include <linux/virtio_mdev_ops.h>
>>> +
>>> +#include "vhost.h"
>>> +
>>> +enum {
>>> +=09VHOST_MDEV_FEATURES =3D
>>> +=09=09(1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
>>> +=09=09(1ULL << VIRTIO_F_ANY_LAYOUT) |
>>> +=09=09(1ULL << VIRTIO_F_VERSION_1) |
>>> +=09=09(1ULL << VIRTIO_F_IOMMU_PLATFORM) |
>>> +=09=09(1ULL << VIRTIO_F_RING_PACKED) |
>>> +=09=09(1ULL << VIRTIO_F_ORDER_PLATFORM) |
>>> +=09=09(1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
>>> +=09=09(1ULL << VIRTIO_RING_F_EVENT_IDX),
>>> +
>>> +=09VHOST_MDEV_NET_FEATURES =3D VHOST_MDEV_FEATURES |
>>> +=09=09(1ULL << VIRTIO_NET_F_CSUM) |
>>> +=09=09(1ULL << VIRTIO_NET_F_GUEST_CSUM) |
>>> +=09=09(1ULL << VIRTIO_NET_F_MTU) |
>>> +=09=09(1ULL << VIRTIO_NET_F_MAC) |
>>> +=09=09(1ULL << VIRTIO_NET_F_GUEST_TSO4) |
>>> +=09=09(1ULL << VIRTIO_NET_F_GUEST_TSO6) |
>>> +=09=09(1ULL << VIRTIO_NET_F_GUEST_ECN) |
>>> +=09=09(1ULL << VIRTIO_NET_F_GUEST_UFO) |
>>> +=09=09(1ULL << VIRTIO_NET_F_HOST_TSO4) |
>>> +=09=09(1ULL << VIRTIO_NET_F_HOST_TSO6) |
>>> +=09=09(1ULL << VIRTIO_NET_F_HOST_ECN) |
>>> +=09=09(1ULL << VIRTIO_NET_F_HOST_UFO) |
>>> +=09=09(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
>>> +=09=09(1ULL << VIRTIO_NET_F_STATUS) |
>>> +=09=09(1ULL << VIRTIO_NET_F_SPEED_DUPLEX),
>>> +};
>>> +
>>> +/* Currently, only network backend w/o multiqueue is supported. */
>>> +#define VHOST_MDEV_VQ_MAX=092
>>> +
>>> +struct vhost_mdev {
>>> +=09/* The lock is to protect this structure. */
>>> +=09struct mutex mutex;
>>> +=09struct vhost_dev dev;
>>> +=09struct vhost_virtqueue *vqs;
>>> +=09int nvqs;
>>> +=09int virtio_id;
>>> +=09bool opened;
>>> +=09struct mdev_device *mdev;
>>> +};
>>> +
>>> +static const u64 vhost_mdev_features[] =3D {
>>> +=09[VIRTIO_ID_NET] =3D VHOST_MDEV_NET_FEATURES,
>>> +};
>>> +
>>> +static void handle_vq_kick(struct vhost_work *work)
>>> +{
>>> +=09struct vhost_virtqueue *vq =3D container_of(work, struct vhost_virt=
queue,
>>> +=09=09=09=09=09=09  poll.work);
>>> +=09struct vhost_mdev *m =3D container_of(vq->dev, struct vhost_mdev, d=
ev);
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(m->=
mdev);
>>> +
>>> +=09ops->kick_vq(m->mdev, vq - m->vqs);
>>> +}
>>> +
>>> +static irqreturn_t vhost_mdev_virtqueue_cb(void *private)
>>> +{
>>> +=09struct vhost_virtqueue *vq =3D private;
>>> +=09struct eventfd_ctx *call_ctx =3D vq->call_ctx;
>>> +
>>> +=09if (call_ctx)
>>> +=09=09eventfd_signal(call_ctx, 1);
>>> +
>>> +=09return IRQ_HANDLED;
>>> +}
>>> +
>>> +static void vhost_mdev_reset(struct vhost_mdev *m)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +
>>> +=09ops->set_status(mdev, 0);
>>> +}
>>> +
>>> +static long vhost_mdev_get_device_id(struct vhost_mdev *m, u8 __user *=
argp)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09u32 device_id;
>>> +
>>> +=09device_id =3D ops->get_device_id(mdev);
>>> +
>>> +=09if (copy_to_user(argp, &device_id, sizeof(device_id)))
>>> +=09=09return -EFAULT;
>>> +
>>> +=09return 0;
>>> +}
>>
>> I believe we need get_vendor_id() as well?
> Currently, there is no official way for vendors to do vendor
> specific extensions in vhost-mdev yet. It might be better to
> add this ioctl when we support this.


Good point.


>
>>
>>> +
>>> +static long vhost_mdev_get_status(struct vhost_mdev *m, u8 __user *sta=
tusp)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09u8 status;
>>> +
>>> +=09status =3D ops->get_status(mdev);
>>> +
>>> +=09if (copy_to_user(statusp, &status, sizeof(status)))
>>> +=09=09return -EFAULT;
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_set_status(struct vhost_mdev *m, u8 __user *sta=
tusp)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09u8 status;
>>> +
>>> +=09if (copy_from_user(&status, statusp, sizeof(status)))
>>> +=09=09return -EFAULT;
>>> +
>>> +=09/*
>>> +=09 * Userspace shouldn't remove status bits unless reset the
>>> +=09 * status to 0.
>>> +=09 */
>>> +=09if (status !=3D 0 && (ops->get_status(mdev) & ~status) !=3D 0)
>>> +=09=09return -EINVAL;
>>> +
>>> +=09ops->set_status(mdev, status);
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static int vhost_mdev_config_validate(struct vhost_mdev *m,
>>> +=09=09=09=09      struct vhost_mdev_config *c)
>>> +{
>>> +=09long size =3D 0;
>>> +
>>> +=09switch (m->virtio_id) {
>>> +=09case VIRTIO_ID_NET:
>>> +=09=09size =3D sizeof(struct virtio_net_config);
>>> +=09=09break;
>>> +=09}
>>> +
>>> +=09if (c->len =3D=3D 0)
>>> +=09=09return -EINVAL;
>>> +
>>> +=09if (c->off >=3D size || c->len > size || c->off + c->len > size)
>>> +=09=09return -E2BIG;
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_get_config(struct vhost_mdev *m,
>>> +=09=09=09=09  struct vhost_mdev_config __user *c)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09struct vhost_mdev_config config;
>>> +=09unsigned long size =3D offsetof(struct vhost_mdev_config, buf);
>>> +=09u8 *buf;
>>> +
>>> +=09if (copy_from_user(&config, c, size))
>>> +=09=09return -EFAULT;
>>> +=09if (vhost_mdev_config_validate(m, &config))
>>> +=09=09return -EINVAL;
>>
>> I think it's better to let the parent to do such validation. Especially
>> consider that the size of config may depend on feature (e.g MQ).
> Above check is just a basic sanity check to make sure
> that e.g. we won't alloc a huge amount of memory.


I see.


>
>>
>>> +=09buf =3D kvzalloc(config.len, GFP_KERNEL);
>>> +=09if (!buf)
>>> +=09=09return -ENOMEM;
>>> +
>>> +=09ops->get_config(mdev, config.off, buf, config.len);
>>> +
>>> +=09if (copy_to_user(c->buf, buf, config.len)) {
>>> +=09=09kvfree(buf);
>>> +=09=09return -EFAULT;
>>> +=09}
>>> +
>>> +=09kvfree(buf);
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_set_config(struct vhost_mdev *m,
>>> +=09=09=09=09  struct vhost_mdev_config __user *c)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09struct vhost_mdev_config config;
>>> +=09unsigned long size =3D offsetof(struct vhost_mdev_config, buf);
>>> +=09u8 *buf;
>>> +
>>> +=09if (copy_from_user(&config, c, size))
>>> +=09=09return -EFAULT;
>>> +=09if (vhost_mdev_config_validate(m, &config))
>>> +=09=09return -EINVAL;
>>> +=09buf =3D kvzalloc(config.len, GFP_KERNEL);
>>> +=09if (!buf)
>>> +=09=09return -ENOMEM;
>>> +
>>> +=09if (copy_from_user(buf, c->buf, config.len)) {
>>> +=09=09kvfree(buf);
>>> +=09=09return -EFAULT;
>>> +=09}
>>> +
>>> +=09ops->set_config(mdev, config.off, buf, config.len);
>>> +
>>> +=09kvfree(buf);
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_get_features(struct vhost_mdev *m, u64 __user *=
featurep)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09u64 features;
>>> +
>>> +=09features =3D ops->get_features(mdev);
>>> +=09features &=3D vhost_mdev_features[m->virtio_id];
>>> +
>>> +=09if (copy_to_user(featurep, &features, sizeof(features)))
>>> +=09=09return -EFAULT;
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_set_features(struct vhost_mdev *m, u64 __user *=
featurep)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09u64 features;
>>> +
>>> +=09/*
>>> +=09 * It's not allowed to change the features after they have
>>> +=09 * been negotiated.
>>> +=09 */
>>> +=09if (ops->get_status(mdev) & VIRTIO_CONFIG_S_FEATURES_OK)
>>> +=09=09return -EBUSY;
>>> +
>>> +=09if (copy_from_user(&features, featurep, sizeof(features)))
>>> +=09=09return -EFAULT;
>>> +
>>> +=09if (features & ~vhost_mdev_features[m->virtio_id])
>>> +=09=09return -EINVAL;
>>> +
>>> +=09if (ops->set_features(mdev, features))
>>> +=09=09return -EINVAL;
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_get_vring_num(struct vhost_mdev *m, u16 __user =
*argp)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09u16 num;
>>> +
>>> +=09num =3D ops->get_vq_num_max(mdev);
>>> +
>>> +=09if (copy_to_user(argp, &num, sizeof(num)))
>>> +=09=09return -EFAULT;
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static long vhost_mdev_vring_ioctl(struct vhost_mdev *m, unsigned int =
cmd,
>>> +=09=09=09=09   void __user *argp)
>>> +{
>>> +=09struct mdev_device *mdev =3D m->mdev;
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09struct virtio_mdev_callback cb;
>>> +=09struct vhost_virtqueue *vq;
>>> +=09struct vhost_vring_state s;
>>> +=09u8 status;
>>> +=09u32 idx;
>>> +=09long r;
>>> +
>>> +=09r =3D get_user(idx, (u32 __user *)argp);
>>> +=09if (r < 0)
>>> +=09=09return r;
>>> +=09if (idx >=3D m->nvqs)
>>> +=09=09return -ENOBUFS;
>>> +
>>> +=09status =3D ops->get_status(mdev);
>>> +
>>> +=09/*
>>> +=09 * It's not allowed to detect and program vqs before
>>> +=09 * features negotiation or after enabling driver.
>>> +=09 */
>>> +=09if (!(status & VIRTIO_CONFIG_S_FEATURES_OK) ||
>>> +=09    (status & VIRTIO_CONFIG_S_DRIVER_OK))
>>> +=09=09return -EBUSY;
>>> +
>>> +=09vq =3D &m->vqs[idx];
>>> +
>>> +=09if (cmd =3D=3D VHOST_MDEV_SET_VRING_ENABLE) {
>>> +=09=09if (copy_from_user(&s, argp, sizeof(s)))
>>> +=09=09=09return -EFAULT;
>>> +=09=09ops->set_vq_ready(mdev, idx, s.num);
>>> +=09=09return 0;
>>> +=09}
>>> +
>>> +=09/*
>>> +=09 * It's not allowed to detect and program vqs with
>>> +=09 * vqs enabled.
>>> +=09 */
>>> +=09if (ops->get_vq_ready(mdev, idx))
>>> +=09=09return -EBUSY;
>>> +
>>> +=09if (cmd =3D=3D VHOST_GET_VRING_BASE)
>>> +=09=09vq->last_avail_idx =3D ops->get_vq_state(m->mdev, idx);
>>> +
>>> +=09r =3D vhost_vring_ioctl(&m->dev, cmd, argp);
>>> +=09if (r)
>>> +=09=09return r;
>>> +
>>> +=09switch (cmd) {
>>> +=09case VHOST_SET_VRING_ADDR:
>>> +=09=09/*
>>> +=09=09 * In vhost-mdev, the ring addresses set by userspace should
>>> +=09=09 * be the DMA addresses within the VFIO container/group.
>>> +=09=09 */
>>> +=09=09if (ops->set_vq_address(mdev, idx, (u64)vq->desc,
>>> +=09=09=09=09=09(u64)vq->avail, (u64)vq->used))
>>> +=09=09=09r =3D -ENODEV;
>>
>> Nit: It looks to me that we need expose alignment of vq to userspace
>> (get_vq_align()).
> Guest drivers are using (maybe hardcoded) alignments based
> on the alignment requirements defined in the spec. It might
> be better to let backends follow the same standard for the
> compatibility.


Ok.

Thanks


>
>> Thanks
>>
>>
>>> +=09=09break;
>>> +
>>> +=09case VHOST_SET_VRING_BASE:
>>> +=09=09if (ops->set_vq_state(mdev, idx, vq->last_avail_idx))
>>> +=09=09=09r =3D -ENODEV;
>>> +=09=09break;
>>> +
>>> +=09case VHOST_SET_VRING_CALL:
>>> +=09=09if (vq->call_ctx) {
>>> +=09=09=09cb.callback =3D vhost_mdev_virtqueue_cb;
>>> +=09=09=09cb.private =3D vq;
>>> +=09=09} else {
>>> +=09=09=09cb.callback =3D NULL;
>>> +=09=09=09cb.private =3D NULL;
>>> +=09=09}
>>> +=09=09ops->set_vq_cb(mdev, idx, &cb);
>>> +=09=09break;
>>> +
>>> +=09case VHOST_SET_VRING_NUM:
>>> +=09=09ops->set_vq_num(mdev, idx, vq->num);
>>> +=09=09break;
>>> +=09}
>>> +
>>> +=09return r;
>>> +}
>>> +
>>> +static int vhost_mdev_open(void *device_data)
>>> +{
>>> +=09struct vhost_mdev *m =3D device_data;
>>> +=09struct vhost_dev *dev;
>>> +=09struct vhost_virtqueue **vqs;
>>> +=09int nvqs, i, r;
>>> +
>>> +=09if (!try_module_get(THIS_MODULE))
>>> +=09=09return -ENODEV;
>>> +
>>> +=09mutex_lock(&m->mutex);
>>> +
>>> +=09if (m->opened) {
>>> +=09=09r =3D -EBUSY;
>>> +=09=09goto err;
>>> +=09}
>>> +
>>> +=09nvqs =3D m->nvqs;
>>> +=09vhost_mdev_reset(m);
>>> +
>>> +=09vqs =3D kmalloc_array(nvqs, sizeof(*vqs), GFP_KERNEL);
>>> +=09if (!vqs) {
>>> +=09=09r =3D -ENOMEM;
>>> +=09=09goto err;
>>> +=09}
>>> +
>>> +=09dev =3D &m->dev;
>>> +=09for (i =3D 0; i < nvqs; i++) {
>>> +=09=09vqs[i] =3D &m->vqs[i];
>>> +=09=09vqs[i]->handle_kick =3D handle_vq_kick;
>>> +=09}
>>> +=09vhost_dev_init(dev, vqs, nvqs, 0, 0, 0);
>>> +=09m->opened =3D true;
>>> +=09mutex_unlock(&m->mutex);
>>> +
>>> +=09return 0;
>>> +
>>> +err:
>>> +=09mutex_unlock(&m->mutex);
>>> +=09module_put(THIS_MODULE);
>>> +=09return r;
>>> +}
>>> +
>>> +static void vhost_mdev_release(void *device_data)
>>> +{
>>> +=09struct vhost_mdev *m =3D device_data;
>>> +
>>> +=09mutex_lock(&m->mutex);
>>> +=09vhost_mdev_reset(m);
>>> +=09vhost_dev_stop(&m->dev);
>>> +=09vhost_dev_cleanup(&m->dev);
>>> +
>>> +=09kfree(m->dev.vqs);
>>> +=09m->opened =3D false;
>>> +=09mutex_unlock(&m->mutex);
>>> +=09module_put(THIS_MODULE);
>>> +}
>>> +
>>> +static long vhost_mdev_unlocked_ioctl(void *device_data,
>>> +=09=09=09=09      unsigned int cmd, unsigned long arg)
>>> +{
>>> +=09struct vhost_mdev *m =3D device_data;
>>> +=09void __user *argp =3D (void __user *)arg;
>>> +=09long r;
>>> +
>>> +=09mutex_lock(&m->mutex);
>>> +
>>> +=09switch (cmd) {
>>> +=09case VHOST_MDEV_GET_DEVICE_ID:
>>> +=09=09r =3D vhost_mdev_get_device_id(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_MDEV_GET_STATUS:
>>> +=09=09r =3D vhost_mdev_get_status(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_MDEV_SET_STATUS:
>>> +=09=09r =3D vhost_mdev_set_status(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_MDEV_GET_CONFIG:
>>> +=09=09r =3D vhost_mdev_get_config(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_MDEV_SET_CONFIG:
>>> +=09=09r =3D vhost_mdev_set_config(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_GET_FEATURES:
>>> +=09=09r =3D vhost_mdev_get_features(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_SET_FEATURES:
>>> +=09=09r =3D vhost_mdev_set_features(m, argp);
>>> +=09=09break;
>>> +=09case VHOST_MDEV_GET_VRING_NUM:
>>> +=09=09r =3D vhost_mdev_get_vring_num(m, argp);
>>> +=09=09break;
>>> +=09default:
>>> +=09=09/*
>>> +=09=09 * VHOST_SET_MEM_TABLE, VHOST_SET_LOG_BASE, and
>>> +=09=09 * VHOST_SET_LOG_FD are not used yet.
>>> +=09=09 */
>>> +=09=09r =3D vhost_dev_ioctl(&m->dev, cmd, argp);
>>> +=09=09if (r =3D=3D -ENOIOCTLCMD)
>>> +=09=09=09r =3D vhost_mdev_vring_ioctl(m, cmd, argp);
>>> +=09}
>>> +
>>> +=09mutex_unlock(&m->mutex);
>>> +=09return r;
>>> +}
>>> +
>>> +static const struct vfio_device_ops vfio_vhost_mdev_dev_ops =3D {
>>> +=09.name=09=09=3D "vfio-vhost-mdev",
>>> +=09.open=09=09=3D vhost_mdev_open,
>>> +=09.release=09=3D vhost_mdev_release,
>>> +=09.ioctl=09=09=3D vhost_mdev_unlocked_ioctl,
>>> +};
>>> +
>>> +static int vhost_mdev_probe(struct device *dev)
>>> +{
>>> +=09struct mdev_device *mdev =3D mdev_from_dev(dev);
>>> +=09const struct virtio_mdev_device_ops *ops =3D mdev_get_vhost_ops(mde=
v);
>>> +=09struct vhost_mdev *m;
>>> +=09int nvqs, r;
>>> +
>>> +=09/* Currently, we only accept the network devices. */
>>> +=09if (ops->get_device_id(mdev) !=3D VIRTIO_ID_NET)
>>> +=09=09return -ENOTSUPP;
>>> +
>>> +=09if (ops->get_mdev_features(mdev) !=3D VIRTIO_MDEV_F_VERSION_1)
>>> +=09=09return -ENOTSUPP;
>>> +
>>> +=09m =3D devm_kzalloc(dev, sizeof(*m), GFP_KERNEL | __GFP_RETRY_MAYFAI=
L);
>>> +=09if (!m)
>>> +=09=09return -ENOMEM;
>>> +
>>> +=09nvqs =3D VHOST_MDEV_VQ_MAX;
>>> +
>>> +=09m->vqs =3D devm_kmalloc_array(dev, nvqs, sizeof(struct vhost_virtqu=
eue),
>>> +=09=09=09=09    GFP_KERNEL);
>>> +=09if (!m->vqs)
>>> +=09=09return -ENOMEM;
>>> +
>>> +=09mutex_init(&m->mutex);
>>> +
>>> +=09m->mdev =3D mdev;
>>> +=09m->nvqs =3D nvqs;
>>> +=09m->virtio_id =3D ops->get_device_id(mdev);
>>> +
>>> +=09r =3D vfio_add_group_dev(dev, &vfio_vhost_mdev_dev_ops, m);
>>> +=09if (r) {
>>> +=09=09mutex_destroy(&m->mutex);
>>> +=09=09return r;
>>> +=09}
>>> +
>>> +=09return 0;
>>> +}
>>> +
>>> +static void vhost_mdev_remove(struct device *dev)
>>> +{
>>> +=09struct vhost_mdev *m;
>>> +
>>> +=09m =3D vfio_del_group_dev(dev);
>>> +=09mutex_destroy(&m->mutex);
>>> +}
>>> +
>>> +static const struct mdev_class_id vhost_mdev_match[] =3D {
>>> +=09{ MDEV_CLASS_ID_VHOST },
>>> +=09{ 0 },
>>> +};
>>> +MODULE_DEVICE_TABLE(mdev, vhost_mdev_match);
>>> +
>>> +static struct mdev_driver vhost_mdev_driver =3D {
>>> +=09.name=09=3D "vhost_mdev",
>>> +=09.probe=09=3D vhost_mdev_probe,
>>> +=09.remove=09=3D vhost_mdev_remove,
>>> +=09.id_table =3D vhost_mdev_match,
>>> +};
>>> +
>>> +static int __init vhost_mdev_init(void)
>>> +{
>>> +=09return mdev_register_driver(&vhost_mdev_driver, THIS_MODULE);
>>> +}
>>> +module_init(vhost_mdev_init);
>>> +
>>> +static void __exit vhost_mdev_exit(void)
>>> +{
>>> +=09mdev_unregister_driver(&vhost_mdev_driver);
>>> +}
>>> +module_exit(vhost_mdev_exit);
>>> +
>>> +MODULE_VERSION("0.0.1");
>>> +MODULE_LICENSE("GPL v2");
>>> +MODULE_AUTHOR("Intel Corporation");
>>> +MODULE_DESCRIPTION("Mediated device based accelerator for virtio");
>>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>>> index 9b69b0bbebfd..3e1e03926355 100644
>>> --- a/include/linux/mdev.h
>>> +++ b/include/linux/mdev.h
>>> @@ -117,6 +117,10 @@ void mdev_set_virtio_ops(struct mdev_device *mdev,
>>>  =09=09=09 const struct virtio_mdev_device_ops *virtio_ops);
>>>  const struct virtio_mdev_device_ops *
>>>  mdev_get_virtio_ops(struct mdev_device *mdev);
>>> +void mdev_set_vhost_ops(struct mdev_device *mdev,
>>> +=09=09=09const struct virtio_mdev_device_ops *vhost_ops);
>>> +const struct virtio_mdev_device_ops *
>>> +mdev_get_vhost_ops(struct mdev_device *mdev);
>>> =20
>>>  extern struct bus_type mdev_bus_type;
>>> =20
>>> @@ -133,6 +137,7 @@ struct mdev_device *mdev_from_dev(struct device *de=
v);
>>>  enum {
>>>  =09MDEV_CLASS_ID_VFIO =3D 1,
>>>  =09MDEV_CLASS_ID_VIRTIO =3D 2,
>>> +=09MDEV_CLASS_ID_VHOST =3D 3,
>>>  =09/* New entries must be added here */
>>>  };
>>> =20
>>> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
>>> index 40d028eed645..061a2824a1b3 100644
>>> --- a/include/uapi/linux/vhost.h
>>> +++ b/include/uapi/linux/vhost.h
>>> @@ -116,4 +116,22 @@
>>>  #define VHOST_VSOCK_SET_GUEST_CID=09_IOW(VHOST_VIRTIO, 0x60, __u64)
>>>  #define VHOST_VSOCK_SET_RUNNING=09=09_IOW(VHOST_VIRTIO, 0x61, int)
>>> =20
>>> +/* VHOST_MDEV specific defines */
>>> +
>>> +/* Get the device id. The device ids follow the same definition of
>>> + * the device id defined in virtio-spec. */
>>> +#define VHOST_MDEV_GET_DEVICE_ID=09_IOR(VHOST_VIRTIO, 0x70, __u32)
>>> +/* Get and set the status. The status bits follow the same definition
>>> + * of the device status defined in virtio-spec. */
>>> +#define VHOST_MDEV_GET_STATUS=09=09_IOR(VHOST_VIRTIO, 0x71, __u8)
>>> +#define VHOST_MDEV_SET_STATUS=09=09_IOW(VHOST_VIRTIO, 0x72, __u8)
>>> +/* Get and set the device config. The device config follows the same
>>> + * definition of the device config defined in virtio-spec. */
>>> +#define VHOST_MDEV_GET_CONFIG=09=09_IOR(VHOST_VIRTIO, 0x73, struct vho=
st_mdev_config)
>>> +#define VHOST_MDEV_SET_CONFIG=09=09_IOW(VHOST_VIRTIO, 0x74, struct vho=
st_mdev_config)
>>> +/* Enable/disable the ring. */
>>> +#define VHOST_MDEV_SET_VRING_ENABLE=09_IOW(VHOST_VIRTIO, 0x75, struct =
vhost_vring_state)
>>> +/* Get the max ring size. */
>>> +#define VHOST_MDEV_GET_VRING_NUM=09_IOR(VHOST_VIRTIO, 0x76, __u16)
>>> +
>>>  #endif
>>> diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhos=
t_types.h
>>> index c907290ff065..7b105d0b2fb9 100644
>>> --- a/include/uapi/linux/vhost_types.h
>>> +++ b/include/uapi/linux/vhost_types.h
>>> @@ -119,6 +119,14 @@ struct vhost_scsi_target {
>>>  =09unsigned short reserved;
>>>  };
>>> =20
>>> +/* VHOST_MDEV specific definitions */
>>> +
>>> +struct vhost_mdev_config {
>>> +=09__u32 off;
>>> +=09__u32 len;
>>> +=09__u8 buf[0];
>>> +};
>>> +
>>>  /* Feature bits */
>>>  /* Log all write descriptors. Can be changed while device is active. *=
/
>>>  #define VHOST_F_LOG_ALL 26