On Tue, Oct 22, 2019 at 09:30:16PM +0800, Jason Wang wrote: > On 2019/10/22 下午5:52, 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. > > > > Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx> > > --- > > This patch depends on below series: > > https://lkml.org/lkml/2019/10/17/286 > > > > 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; > > > Any idea on how to extend it to support devices other than net? I think we > want a generic API or an API that could be made generic in the future. > > Do we want to e.g having a generic vhost mdev for all kinds of devices or > introducing e.g vhost-net-mdev and vhost-scsi-mdev? One possible way is to do what vhost-user does. I.e. Apart from the generic ring, features, ... related ioctls, we also introduce device specific ioctls when we need them. As vhost-mdev just needs to forward configs between parent and userspace and even won't cache any info when possible, I think it might be better to do this in one generic vhost-mdev module. > > > > - 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 | 12 + > > drivers/vhost/Kconfig | 9 + > > drivers/vhost/Makefile | 3 + > > drivers/vhost/mdev.c | 415 ++++++++++++++++++++++++++++++++++ > > include/linux/mdev.h | 3 + > > include/uapi/linux/vhost.h | 13 ++ > > 6 files changed, 455 insertions(+) > > create mode 100644 drivers/vhost/mdev.c > > > > diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c > > index 5834f6b7c7a5..2963f65e6648 100644 > > --- a/drivers/vfio/mdev/mdev_core.c > > +++ b/drivers/vfio/mdev/mdev_core.c > > @@ -69,6 +69,18 @@ void mdev_set_virtio_ops(struct mdev_device *mdev, > > } > > EXPORT_SYMBOL(mdev_set_virtio_ops); > > +/* 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, > > + const struct virtio_mdev_device_ops *vhost_ops) > > +{ > > + WARN_ON(mdev->class_id); > > + mdev->class_id = MDEV_CLASS_ID_VHOST; > > + mdev->device_ops = vhost_ops; > > +} > > +EXPORT_SYMBOL(mdev_set_vhost_ops); > > + > > const void *mdev_get_dev_ops(struct mdev_device *mdev) > > { > > return mdev->device_ops; > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig > > index 3d03ccbd1adc..7b5c2f655af7 100644 > > --- a/drivers/vhost/Kconfig > > +++ b/drivers/vhost/Kconfig > > @@ -34,6 +34,15 @@ config VHOST_VSOCK > > To compile this driver as a module, choose M here: the module will be called > > vhost_vsock. > > +config VHOST_MDEV > > + tristate "Vhost driver for Mediated devices" > > + depends on EVENTFD && VFIO && VFIO_MDEV > > + select VHOST > > + default n > > + ---help--- > > + Say M here to enable the vhost_mdev module for use with > > + the mediated device based hardware vhost accelerators. > > + > > config VHOST > > tristate > > ---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 := vsock.o > > obj-$(CONFIG_VHOST_RING) += vringh.o > > +obj-$(CONFIG_VHOST_MDEV) += vhost_mdev.o > > +vhost_mdev-y := mdev.o > > + > > obj-$(CONFIG_VHOST) += vhost.o > > diff --git a/drivers/vhost/mdev.c b/drivers/vhost/mdev.c > > new file mode 100644 > > index 000000000000..5f9cae61018c > > --- /dev/null > > +++ b/drivers/vhost/mdev.c > > @@ -0,0 +1,415 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Copyright (C) 2018-2019 Intel Corporation. > > + */ > > + > > +#include <linux/compat.h> > > +#include <linux/kernel.h> > > +#include <linux/miscdevice.h> > > +#include <linux/mdev.h> > > +#include <linux/module.h> > > +#include <linux/vfio.h> > > +#include <linux/vhost.h> > > +#include <linux/virtio_mdev.h> > > +#include <linux/virtio_ids.h> > > + > > +#include "vhost.h" > > + > > +/* Currently, only network backend w/o multiqueue is supported. */ > > +#define VHOST_MDEV_VQ_MAX 2 > > + > > +struct vhost_mdev { > > + /* The lock is to protect this structure. */ > > + struct mutex mutex; > > + struct vhost_dev dev; > > + struct vhost_virtqueue *vqs; > > + int nvqs; > > + u64 status; > > + u64 features; > > + u64 acked_features; > > + bool opened; > > + struct mdev_device *mdev; > > +}; > > + > > +static void handle_vq_kick(struct vhost_work *work) > > +{ > > + struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue, > > + poll.work); > > + struct vhost_mdev *m = container_of(vq->dev, struct vhost_mdev, dev); > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(m->mdev); > > + > > + ops->kick_vq(m->mdev, vq - m->vqs); > > +} > > + > > +static irqreturn_t vhost_mdev_virtqueue_cb(void *private) > > +{ > > + struct vhost_virtqueue *vq = private; > > + struct eventfd_ctx *call_ctx = vq->call_ctx; > > + > > + if (call_ctx) > > + eventfd_signal(call_ctx, 1); > > + return IRQ_HANDLED; > > +} > > + > > +static void vhost_mdev_reset(struct vhost_mdev *m) > > +{ > > + struct mdev_device *mdev = m->mdev; > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev); > > + > > + m->status = 0; > > + return ops->set_status(mdev, m->status); > > +} > > + > > +static long vhost_mdev_get_status(struct vhost_mdev *m, u8 __user *statusp) > > +{ > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(m->mdev); > > + struct mdev_device *mdev = m->mdev; > > + u8 status; > > + > > + status = ops->get_status(mdev); > > + m->status = status; > > + > > + if (copy_to_user(statusp, &status, sizeof(status))) > > + return -EFAULT; > > + > > + return 0; > > +} > > + > > +static long vhost_mdev_set_status(struct vhost_mdev *m, u8 __user *statusp) > > +{ > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(m->mdev); > > + struct mdev_device *mdev = m->mdev; > > + u8 status; > > + > > + if (copy_from_user(&status, statusp, sizeof(status))) > > + return -EFAULT; > > + > > + /* > > + * Userspace shouldn't remove status bits unless reset the > > + * status to 0. > > + */ > > + if (status != 0 && (m->status & ~status) != 0) > > + return -EINVAL; > > > We don't cache vq ready information but we cache status and features here, > any reason for this? +1, I think it's better to not cache any unnecessary information in vhost-mdev. > > > > + > > + ops->set_status(mdev, status); > > + m->status = ops->get_status(mdev); > > + > > + return 0; > > +} > > + > > +static long vhost_mdev_get_features(struct vhost_mdev *m, u64 __user *featurep) > > +{ > > + if (copy_to_user(featurep, &m->features, sizeof(m->features))) > > + return -EFAULT; > > > As discussed in previous version do we need to filter out MQ feature here? I think it's more straightforward to let the parent drivers to filter out the unsupported features. Otherwise it would be tricky when we want to add more features in vhost-mdev module, i.e. if the parent drivers may expose unsupported features and relay on vhost-mdev to filter them out, these features will be exposed to userspace automatically when they are enabled in vhost-mdev in the future. > > > > + return 0; > > +} > > + > > +static long vhost_mdev_set_features(struct vhost_mdev *m, u64 __user *featurep) > > +{ > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(m->mdev); > > + struct mdev_device *mdev = m->mdev; > > + u64 features; > > + > > + /* > > + * It's not allowed to change the features after they have > > + * been negotiated. > > + */ > > + if (m->status & VIRTIO_CONFIG_S_FEATURES_OK) > > + return -EPERM; > > > -EBUSY? Yeah, definitely. > > > > + > > + if (copy_from_user(&features, featurep, sizeof(features))) > > + return -EFAULT; > > + > > + if (features & ~m->features) > > + return -EINVAL; > > + > > + m->acked_features = features; > > + if (ops->set_features(mdev, m->acked_features)) > > + return -ENODEV; > > > -EINVAL should be better, this would be more obvious for parent that wants > to force any feature. +1. Agree. > > > > + > > + return 0; > > +} > > + > > +static long vhost_mdev_get_vring_num(struct vhost_mdev *m, u16 __user *argp) > > +{ > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(m->mdev); > > + struct mdev_device *mdev = m->mdev; > > + u16 num; > > + > > + num = ops->get_vq_num_max(mdev); > > + > > + if (copy_to_user(argp, &num, sizeof(num))) > > + return -EFAULT; > > + return 0; > > +} > > + > > +static long vhost_mdev_get_queue_num(struct vhost_mdev *m, u32 __user *argp) > > +{ > > + u32 nvqs = m->nvqs; > > + > > + if (copy_to_user(argp, &nvqs, sizeof(nvqs))) > > + return -EFAULT; > > + return 0; > > +} > > + > > +static long vhost_mdev_vring_ioctl(struct vhost_mdev *m, unsigned int cmd, > > + void __user *argp) > > +{ > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(m->mdev); > > + struct mdev_device *mdev = m->mdev; > > + struct virtio_mdev_callback cb; > > + struct vhost_virtqueue *vq; > > + struct vhost_vring_state s; > > + u32 idx; > > + long r; > > + > > + r = get_user(idx, (u32 __user *)argp); > > + if (r < 0) > > + return r; > > + if (idx >= m->nvqs) > > + return -ENOBUFS; > > + > > + /* > > + * It's not allowed to detect and program vqs before > > + * features negotiation or after enabling driver. > > + */ > > + if (!(m->status & VIRTIO_CONFIG_S_FEATURES_OK) || > > + (m->status & VIRTIO_CONFIG_S_DRIVER_OK)) > > + return -EPERM; > > > So the question is: is it better to do this in parent or not? I think it will duplicate the generic code in each parent. > > > > + > > + vq = &m->vqs[idx]; > > + > > + if (cmd == VHOST_MDEV_SET_VRING_ENABLE) { > > + if (copy_from_user(&s, argp, sizeof(s))) > > + return -EFAULT; > > + ops->set_vq_ready(mdev, idx, s.num); > > + return 0; > > + } > > + > > + /* > > + * It's not allowed to detect and program vqs with > > + * vqs enabled. > > + */ > > + if (ops->get_vq_ready(mdev, idx)) > > + return -EPERM; > > + > > + if (cmd == VHOST_GET_VRING_BASE) > > + vq->last_avail_idx = ops->get_vq_state(m->mdev, idx); > > + > > + r = vhost_vring_ioctl(&m->dev, cmd, argp); > > + if (r) > > + return r; > > + > > + switch (cmd) { > > + case VHOST_SET_VRING_ADDR: > > + /* > > + * In vhost-mdev, the ring addresses set by userspace should > > + * be the DMA addresses within the VFIO container/group. > > + */ > > + if (ops->set_vq_address(mdev, idx, (u64)vq->desc, > > + (u64)vq->avail, (u64)vq->used)) > > + r = -ENODEV; > > + break; > > + > > + case VHOST_SET_VRING_BASE: > > + if (ops->set_vq_state(mdev, idx, vq->last_avail_idx)) > > + r = -ENODEV; > > + break; > > + > > + case VHOST_SET_VRING_CALL: > > + if (vq->call_ctx) { > > + cb.callback = vhost_mdev_virtqueue_cb; > > + cb.private = vq; > > + } else { > > + cb.callback = NULL; > > + cb.private = NULL; > > + } > > + ops->set_vq_cb(mdev, idx, &cb); > > + break; > > + > > + case VHOST_SET_VRING_NUM: > > + ops->set_vq_num(mdev, idx, vq->num); > > + break; > > + } > > + > > + return r; > > +} > > + > > +static int vhost_mdev_open(void *device_data) > > +{ > > + struct vhost_mdev *m = device_data; > > + struct vhost_dev *dev; > > + struct vhost_virtqueue **vqs; > > + int nvqs, i, r; > > + > > + if (!try_module_get(THIS_MODULE)) > > + return -ENODEV; > > + > > + mutex_lock(&m->mutex); > > + > > + if (m->opened) { > > + r = -EBUSY; > > + goto err; > > + } > > + > > + nvqs = m->nvqs; > > + vhost_mdev_reset(m); > > + > > + memset(&m->dev, 0, sizeof(m->dev)); > > + memset(m->vqs, 0, nvqs * sizeof(struct vhost_virtqueue)); > > + > > + vqs = kmalloc_array(nvqs, sizeof(*vqs), GFP_KERNEL); > > + if (!vqs) { > > + r = -ENOMEM; > > + goto err; > > + } > > + > > + dev = &m->dev; > > + for (i = 0; i < nvqs; i++) { > > + vqs[i] = &m->vqs[i]; > > + vqs[i]->handle_kick = handle_vq_kick; > > + } > > + vhost_dev_init(dev, vqs, nvqs, 0, 0, 0); > > + m->opened = true; > > + mutex_unlock(&m->mutex); > > + > > + return 0; > > + > > +err: > > + mutex_unlock(&m->mutex); > > + module_put(THIS_MODULE); > > + return r; > > +} > > + > > +static void vhost_mdev_release(void *device_data) > > +{ > > + struct vhost_mdev *m = device_data; > > + > > + mutex_lock(&m->mutex); > > + vhost_mdev_reset(m); > > + vhost_dev_stop(&m->dev); > > + vhost_dev_cleanup(&m->dev); > > + > > + kfree(m->dev.vqs); > > + m->opened = false; > > + mutex_unlock(&m->mutex); > > + module_put(THIS_MODULE); > > +} > > + > > +static long vhost_mdev_unlocked_ioctl(void *device_data, > > + unsigned int cmd, unsigned long arg) > > +{ > > + struct vhost_mdev *m = device_data; > > + void __user *argp = (void __user *)arg; > > + long r; > > + > > + mutex_lock(&m->mutex); > > + > > + switch (cmd) { > > + case VHOST_MDEV_GET_STATUS: > > + r = vhost_mdev_get_status(m, argp); > > + break; > > + case VHOST_MDEV_SET_STATUS: > > + r = vhost_mdev_set_status(m, argp); > > + break; > > + case VHOST_GET_FEATURES: > > + r = vhost_mdev_get_features(m, argp); > > + break; > > + case VHOST_SET_FEATURES: > > + r = vhost_mdev_set_features(m, argp); > > + break; > > + case VHOST_MDEV_GET_VRING_NUM: > > + r = vhost_mdev_get_vring_num(m, argp); > > + break; > > + case VHOST_MDEV_GET_QUEUE_NUM: > > + r = vhost_mdev_get_queue_num(m, argp); > > + break; > > > It's not clear to me that how this API will be used by userspace? I think > e.g features without MQ implies the queue num here. I was thinking about always letting _GET_QUEUE_NUM return the supported number of queues. For virtio devices other than virtio-net, can we always expect to have a fixed default number of queues when there is no MQ feature? > > > > + default: > > + r = vhost_dev_ioctl(&m->dev, cmd, argp); > > > I believe having SET_MEM_TABLE/SET_LOG_BASE/SET_LOG_FD is for future > support of those features. If it's true need add some comments on this. OK. > > > > + if (r == -ENOIOCTLCMD) > > + r = vhost_mdev_vring_ioctl(m, cmd, argp); > > + } > > + > > + mutex_unlock(&m->mutex); > > + return r; > > +} > > + > > +static const struct vfio_device_ops vfio_vhost_mdev_dev_ops = { > > + .name = "vfio-vhost-mdev", > > + .open = vhost_mdev_open, > > + .release = vhost_mdev_release, > > + .ioctl = vhost_mdev_unlocked_ioctl, > > +}; > > + > > +static int vhost_mdev_probe(struct device *dev) > > +{ > > + struct mdev_device *mdev = mdev_from_dev(dev); > > + const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev); > > + struct vhost_mdev *m; > > + int nvqs, r; > > + > > + /* Currently, only network backend is supported. */ > > + if (ops->get_device_id(mdev) != VIRTIO_ID_NET) > > + return -ENOTSUPP; > > > If we decide to go with the way of vhost-net-mdev, probably need something > smarter. E.g a vhost bus etc. > > > > + > > + if (ops->get_mdev_features(mdev) != VIRTIO_MDEV_F_VERSION_1) > > + return -ENOTSUPP; > > + > > + m = devm_kzalloc(dev, sizeof(*m), GFP_KERNEL | __GFP_RETRY_MAYFAIL); > > + if (!m) > > + return -ENOMEM; > > + > > + nvqs = VHOST_MDEV_VQ_MAX; > > + m->nvqs = nvqs; > > + > > + m->vqs = devm_kmalloc_array(dev, nvqs, sizeof(struct vhost_virtqueue), > > + GFP_KERNEL); > > + if (!m->vqs) > > + return -ENOMEM; > > > Is it better to move those allocation to open? Otherwise the memset there > seems strange. OK. > > > > + > > + r = vfio_add_group_dev(dev, &vfio_vhost_mdev_dev_ops, m); > > + if (r) > > + return r; > > + > > + mutex_init(&m->mutex); > > + m->features = ops->get_features(mdev); > > + m->mdev = mdev; > > + return 0; > > +} > > + > > +static void vhost_mdev_remove(struct device *dev) > > +{ > > + struct vhost_mdev *m; > > + > > + m = vfio_del_group_dev(dev); > > + mutex_destroy(&m->mutex); > > +} > > + > > +static const struct mdev_class_id vhost_mdev_match[] = { > > + { MDEV_CLASS_ID_VHOST }, > > + { 0 }, > > +}; > > +MODULE_DEVICE_TABLE(mdev, vhost_mdev_match); > > + > > +static struct mdev_driver vhost_mdev_driver = { > > + .name = "vhost_mdev", > > + .probe = vhost_mdev_probe, > > + .remove = vhost_mdev_remove, > > + .id_table = vhost_mdev_match, > > +}; > > + > > +static int __init vhost_mdev_init(void) > > +{ > > + return mdev_register_driver(&vhost_mdev_driver, THIS_MODULE); > > +} > > +module_init(vhost_mdev_init); > > + > > +static void __exit vhost_mdev_exit(void) > > +{ > > + mdev_unregister_driver(&vhost_mdev_driver); > > +} > > +module_exit(vhost_mdev_exit); > > + > > +MODULE_VERSION("0.0.1"); > > +MODULE_LICENSE("GPL v2"); > > +MODULE_DESCRIPTION("Mediated device based accelerator for virtio"); > > diff --git a/include/linux/mdev.h b/include/linux/mdev.h > > index 13e045e09d3b..6060cdbe6d3e 100644 > > --- a/include/linux/mdev.h > > +++ b/include/linux/mdev.h > > @@ -114,6 +114,8 @@ void mdev_set_vfio_ops(struct mdev_device *mdev, > > const struct vfio_mdev_device_ops *vfio_ops); > > void mdev_set_virtio_ops(struct mdev_device *mdev, > > const struct virtio_mdev_device_ops *virtio_ops); > > +void mdev_set_vhost_ops(struct mdev_device *mdev, > > + const struct virtio_mdev_device_ops *vhost_ops); > > const void *mdev_get_dev_ops(struct mdev_device *mdev); > > extern struct bus_type mdev_bus_type; > > @@ -131,6 +133,7 @@ struct mdev_device *mdev_from_dev(struct device *dev); > > enum { > > MDEV_CLASS_ID_VFIO = 1, > > MDEV_CLASS_ID_VIRTIO = 2, > > + MDEV_CLASS_ID_VHOST = 3, > > /* New entries must be added here */ > > }; > > diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h > > index 40d028eed645..dad3c62bd91b 100644 > > --- a/include/uapi/linux/vhost.h > > +++ b/include/uapi/linux/vhost.h > > @@ -116,4 +116,17 @@ > > #define VHOST_VSOCK_SET_GUEST_CID _IOW(VHOST_VIRTIO, 0x60, __u64) > > #define VHOST_VSOCK_SET_RUNNING _IOW(VHOST_VIRTIO, 0x61, int) > > +/* VHOST_MDEV specific defines */ > > + > > +/* Get and set the status of the backend. The status bits follow the > > + * same definition of the device status defined in virtio-spec. */ > > +#define VHOST_MDEV_GET_STATUS _IOW(VHOST_VIRTIO, 0x70, __u8) > > +#define VHOST_MDEV_SET_STATUS _IOW(VHOST_VIRTIO, 0x71, __u8) > > +/* Enable/disable the ring. */ > > +#define VHOST_MDEV_SET_VRING_ENABLE _IOW(VHOST_VIRTIO, 0x72, struct vhost_vring_state) > > +/* Get the max ring size. */ > > +#define VHOST_MDEV_GET_VRING_NUM _IOW(VHOST_VIRTIO, 0x73, __u16) > > +/* Get the max number of queues. */ > > +#define VHOST_MDEV_GET_QUEUE_NUM _IOW(VHOST_VIRTIO, 0x74, __u32) > > > Do we need API for userspace to get backend capability? (that calls > get_mdev_device_features()) Vhost already has the features and backend features ioctls. In vhost-mdev, it might be better to still just use them to expose the backend capability to userspace. Thanks for the review! Tiwei > > Thanks > > > > + > > #endif >
