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Message-ID: <20191106144952.GA10926@___>
Date: Wed, 6 Nov 2019 22:49:52 +0800
From: Tiwei Bie <tiwei.bie@...el.com>
To: Jason Wang <jasowang@...hat.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, alex.williamson@...hat.com,
maxime.coquelin@...hat.com, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, dan.daly@...el.com,
cunming.liang@...el.com, zhihong.wang@...el.com,
lingshan.zhu@...el.com
Subject: Re: [PATCH v5] vhost: introduce mdev based hardware backend
On Wed, Nov 06, 2019 at 09:20:20PM +0800, Jason Wang wrote:
> On 2019/11/6 下午8:57, Michael S. Tsirkin wrote:
> > On Wed, Nov 06, 2019 at 08:22:50PM +0800, Tiwei Bie wrote:
> > > On Wed, Nov 06, 2019 at 03:54:45PM +0800, Jason Wang wrote:
> > > > On 2019/11/5 下午7:53, 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, userspace can use vhost ioctls on top of it
> > > > > to setup the backend.
> > > > >
> > > > > Signed-off-by: Tiwei Bie <tiwei.bie@...el.com>
> > > >
> > > > Looks good to me. Only minor nits which could be addressed on top.
> > > >
> > > > Reviewed-by: Jason Wang <jasowang@...hat.com>
> > > Thanks!
> > >
> > > >
> > > > > ---
> > > > > This patch depends on below series:
> > > > > https://lkml.org/lkml/2019/11/5/217
> > > > >
> > > > > v4 -> v5:
> > > > > - Rebase on top of virtio-mdev series v8;
> > > > > - Use the virtio_ops of mdev_device in vhost-mdev (Jason);
> > > > > - Some minor improvements on commit log;
> > > > >
> > > > > v3 -> v4:
> > > > > - Rebase on top of virtio-mdev series v6;
> > > > > - Some minor tweaks and improvements;
> > > > >
> > > > > 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 | 21 ++
> > > > > drivers/vhost/Kconfig | 12 +
> > > > > drivers/vhost/Makefile | 3 +
> > > > > drivers/vhost/mdev.c | 553 +++++++++++++++++++++++++++++++
> > > > > include/linux/mdev.h | 5 +
> > > > > include/uapi/linux/vhost.h | 18 +
> > > > > include/uapi/linux/vhost_types.h | 8 +
> > > > > 7 files changed, 620 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 c58253404ed5..d855be5afbae 100644
> > > > > --- a/drivers/vfio/mdev/mdev_core.c
> > > > > +++ b/drivers/vfio/mdev/mdev_core.c
> > > > > @@ -99,6 +99,27 @@ mdev_get_virtio_ops(struct mdev_device *mdev)
> > > > > }
> > > > > EXPORT_SYMBOL(mdev_get_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 mdev_virtio_device_ops *vhost_ops)
> > > > > +{
> > > > > + mdev_set_class(mdev, MDEV_CLASS_ID_VHOST);
> > > > > + mdev->virtio_ops = vhost_ops;
> > > > > +}
> > > > > +EXPORT_SYMBOL(mdev_set_vhost_ops);
> > > > > +
> > > > > +/* Get the vhost device ops for the mdev device. */
> > > > > +const struct mdev_virtio_device_ops *
> > > > > +mdev_get_vhost_ops(struct mdev_device *mdev)
> > > > > +{
> > > > > + WARN_ON(mdev->class_id != MDEV_CLASS_ID_VHOST);
> > > > > + return mdev->virtio_ops;
> > > > > +}
> > > > > +EXPORT_SYMBOL(mdev_get_vhost_ops);
> > > > > +
> > > > > struct device *mdev_dev(struct mdev_device *mdev)
> > > > > {
> > > > > return &mdev->dev;
> > > > > 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
> > > > > 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---
> > > > > + This kernel module can be loaded in host kernel to accelerate
> > > > > + guest virtio devices with the mediated device based backends.
> > > > > +
> > > > > + To compile this driver as a module, choose M here: the module will
> > > > > + be called vhost_mdev.
> > > > > +
> > > > > 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..0bcde0f3a9cd
> > > > > --- /dev/null
> > > > > +++ b/drivers/vhost/mdev.c
> > > > > @@ -0,0 +1,553 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > +/*
> > > > > + * Vhost driver for mediated device based backends.
> > > > > + *
> > > > > + * Copyright (C) 2018-2019 Intel Corporation.
> > > > > + *
> > > > > + * Author: Tiwei Bie <tiwei.bie@...el.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/mdev_virtio_ops.h>
> > > > > +#include <linux/nospec.h>
> > > > > +#include <linux/vfio.h>
> > > > > +#include <linux/vhost.h>
> > > > > +#include <linux/virtio_net.h>
> > > > > +
> > > > > +#include "vhost.h"
> > > > > +
> > > > > +enum {
> > > > > + VHOST_MDEV_FEATURES =
> > > > > + (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
> > > > > + (1ULL << VIRTIO_F_ANY_LAYOUT) |
> > > > > + (1ULL << VIRTIO_F_VERSION_1) |
> > > > > + (1ULL << VIRTIO_F_IOMMU_PLATFORM) |
> > > > > + (1ULL << VIRTIO_F_RING_PACKED) |
> > > > > + (1ULL << VIRTIO_F_ORDER_PLATFORM) |
> > > > > + (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
> > > > > + (1ULL << VIRTIO_RING_F_EVENT_IDX),
> > > > > +
> > > > > + VHOST_MDEV_NET_FEATURES = VHOST_MDEV_FEATURES |
> > > > > + (1ULL << VIRTIO_NET_F_CSUM) |
> > > > > + (1ULL << VIRTIO_NET_F_GUEST_CSUM) |
> > > > > + (1ULL << VIRTIO_NET_F_MTU) |
> > > > > + (1ULL << VIRTIO_NET_F_MAC) |
> > > > > + (1ULL << VIRTIO_NET_F_GUEST_TSO4) |
> > > > > + (1ULL << VIRTIO_NET_F_GUEST_TSO6) |
> > > > > + (1ULL << VIRTIO_NET_F_GUEST_ECN) |
> > > > > + (1ULL << VIRTIO_NET_F_GUEST_UFO) |
> > > > > + (1ULL << VIRTIO_NET_F_HOST_TSO4) |
> > > > > + (1ULL << VIRTIO_NET_F_HOST_TSO6) |
> > > > > + (1ULL << VIRTIO_NET_F_HOST_ECN) |
> > > > > + (1ULL << VIRTIO_NET_F_HOST_UFO) |
> > > > > + (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
> > > > > + (1ULL << VIRTIO_NET_F_STATUS) |
> > > > > + (1ULL << VIRTIO_NET_F_SPEED_DUPLEX),
> > > > > +};
> > > > > +
> > > > > +/* 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;
> > > > > + int virtio_id;
> > > > > + bool opened;
> > > > > + struct mdev_device *mdev;
> > > > > +};
> > > > > +
> > > > > +static const u64 vhost_mdev_features[] = {
> > > > > + [VIRTIO_ID_NET] = VHOST_MDEV_NET_FEATURES,
> > > > > +};
> > > > > +
> > > > > +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 mdev_virtio_device_ops *ops = mdev_get_vhost_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 mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > +
> > > > > + ops->set_status(mdev, 0);
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_get_device_id(struct vhost_mdev *m, u8 __user *argp)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + u32 device_id;
> > > > > +
> > > > > + device_id = ops->get_device_id(mdev);
> > > > > +
> > > > > + if (copy_to_user(argp, &device_id, sizeof(device_id)))
> > > > > + return -EFAULT;
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_get_status(struct vhost_mdev *m, u8 __user *statusp)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + u8 status;
> > > > > +
> > > > > + status = ops->get_status(mdev);
> > > > > +
> > > > > + 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)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(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 && (ops->get_status(mdev) & ~status) != 0)
> > > > > + return -EINVAL;
> > > > > +
> > > > > + ops->set_status(mdev, status);
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static int vhost_mdev_config_validate(struct vhost_mdev *m,
> > > > > + struct vhost_mdev_config *c)
> > > > > +{
> > > > > + long size = 0;
> > > > > +
> > > > > + switch (m->virtio_id) {
> > > > > + case VIRTIO_ID_NET:
> > > > > + size = sizeof(struct virtio_net_config);
> > > > > + break;
> > > > > + }
> > > > > +
> > > > > + if (c->len == 0)
> > > > > + return -EINVAL;
> > > > > +
> > > > > + if (c->off >= size || c->len > size || c->off + c->len > size)
> > > > > + return -E2BIG;
> > > >
> > > > Nit: It should be the same as check with c->off + c->len > size only.
> > > I did a quick test with below program:
> > >
> > > #include <stdio.h>
> > >
> > > int main(void)
> > > {
> > > unsigned int a, b;
> > > long c;
> > >
> > > scanf("%u%u%ld", &a, &b, &c);
> > > printf("%d\n", a + b > c);
> > > printf("%d\n", (long)a + b > c);
> > >
> > > return 0;
> > > }
> > >
> > > And I got this:
> > >
> > > $ echo 4294967295 1 1 | ./a.out
> > > 0
> > > 1
> > >
> > > As c->off and c->len are __u32, we would need to cast one of
> > > them to long if we want to just check c->off + c->len > size,
> > > e.g. (long)c->off + c->len > size
>
>
> I miss that, you're right.
>
>
> > >
> > > Off the topic, one thing I'm not quite sure about and want to
> > > confirm is that, will it be better to define c->off and c->len
> > > as __u64 (they are parts of UAPI)?
> >
> > Can't hurt but then we need to be very careful with range checking.
>
>
> Yes, so I tend to keep the code as is since set/get_config use unsigned int.
I see. Thanks for the confirmation. I will keep the code as is.
>
>
> >
> >
> > > >
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_get_config(struct vhost_mdev *m,
> > > > > + struct vhost_mdev_config __user *c)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + struct vhost_mdev_config config;
> > > > > + unsigned long size = offsetof(struct vhost_mdev_config, buf);
> > > > > + u8 *buf;
> > > > > +
> > > > > + if (copy_from_user(&config, c, size))
> > > > > + return -EFAULT;
> > > > > + if (vhost_mdev_config_validate(m, &config))
> > > > > + return -EINVAL;
> > > > > + buf = kvzalloc(config.len, GFP_KERNEL);
> > > > > + if (!buf)
> > > > > + return -ENOMEM;
> > > > > +
> > > > > + ops->get_config(mdev, config.off, buf, config.len);
> > > > > +
> > > > > + if (copy_to_user(c->buf, buf, config.len)) {
> > > > > + kvfree(buf);
> > > > > + return -EFAULT;
> > > > > + }
> > > > > +
> > > > > + kvfree(buf);
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_set_config(struct vhost_mdev *m,
> > > > > + struct vhost_mdev_config __user *c)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + struct vhost_mdev_config config;
> > > > > + unsigned long size = offsetof(struct vhost_mdev_config, buf);
> > > > > + u8 *buf;
> > > > > +
> > > > > + if (copy_from_user(&config, c, size))
> > > > > + return -EFAULT;
> > > > > + if (vhost_mdev_config_validate(m, &config))
> > > > > + return -EINVAL;
> > > > > + buf = kvzalloc(config.len, GFP_KERNEL);
> > > > > + if (!buf)
> > > > > + return -ENOMEM;
> > > > > +
> > > > > + if (copy_from_user(buf, c->buf, config.len)) {
> > > > > + kvfree(buf);
> > > > > + return -EFAULT;
> > > > > + }
> > > > > +
> > > > > + ops->set_config(mdev, config.off, buf, config.len);
> > > > > +
> > > > > + kvfree(buf);
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_get_features(struct vhost_mdev *m, u64 __user *featurep)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + u64 features;
> > > > > +
> > > > > + features = ops->get_features(mdev);
> > > > > + features &= vhost_mdev_features[m->virtio_id];
> > > > > +
> > > > > + if (copy_to_user(featurep, &features, sizeof(features)))
> > > > > + return -EFAULT;
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_set_features(struct vhost_mdev *m, u64 __user *featurep)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + u64 features;
> > > > > +
> > > > > + /*
> > > > > + * It's not allowed to change the features after they have
> > > > > + * been negotiated.
> > > > > + */
> > > > > + if (ops->get_status(mdev) & VIRTIO_CONFIG_S_FEATURES_OK)
> > > > > + return -EBUSY;
> > > > > +
> > > > > + if (copy_from_user(&features, featurep, sizeof(features)))
> > > > > + return -EFAULT;
> > > > > +
> > > > > + if (features & ~vhost_mdev_features[m->virtio_id])
> > > > > + return -EINVAL;
> > > > > +
> > > > > + if (ops->set_features(mdev, features))
> > > > > + return -EINVAL;
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > +static long vhost_mdev_get_vring_num(struct vhost_mdev *m, u16 __user *argp)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(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_vring_ioctl(struct vhost_mdev *m, unsigned int cmd,
> > > > > + void __user *argp)
> > > > > +{
> > > > > + struct mdev_device *mdev = m->mdev;
> > > > > + const struct mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + struct virtio_mdev_callback cb;
> > > > > + struct vhost_virtqueue *vq;
> > > > > + struct vhost_vring_state s;
> > > > > + u8 status;
> > > > > + u32 idx;
> > > > > + long r;
> > > > > +
> > > > > + r = get_user(idx, (u32 __user *)argp);
> > > > > + if (r < 0)
> > > > > + return r;
> > > > > + if (idx >= m->nvqs)
> > > > > + return -ENOBUFS;
> > > > > +
> > > > > + idx = array_index_nospec(idx, m->nvqs);
> > > > > + vq = &m->vqs[idx];
> > > > > +
> > > > > + status = ops->get_status(mdev);
> > > > > +
> > > > > + /*
> > > > > + * It's not allowed to detect and program vqs before
> > > > > + * features negotiation or after enabling driver.
> > > > > + */
> > > > > + if (!(status & VIRTIO_CONFIG_S_FEATURES_OK) ||
> > > > > + (status & VIRTIO_CONFIG_S_DRIVER_OK))
> > > > > + return -EBUSY;
> > > > > +
> > > > > + 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 -EBUSY;
> > > > > +
> > > > > + 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 = -EINVAL;
> > > > > + break;
> > > > > +
> > > > > + case VHOST_SET_VRING_BASE:
> > > > > + if (ops->set_vq_state(mdev, idx, vq->last_avail_idx))
> > > > > + r = -EINVAL;
> > > > > + 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);
> > > > > +
> > > > > + 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_DEVICE_ID:
> > > > > + r = vhost_mdev_get_device_id(m, argp);
> > > > > + break;
> > > > > + 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_MDEV_GET_CONFIG:
> > > > > + r = vhost_mdev_get_config(m, argp);
> > > > > + break;
> > > > > + case VHOST_MDEV_SET_CONFIG:
> > > > > + r = vhost_mdev_set_config(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;
> > > > > + default:
> > > > > + /*
> > > > > + * VHOST_SET_MEM_TABLE, VHOST_SET_LOG_BASE, and
> > > > > + * VHOST_SET_LOG_FD are not used yet.
> > > > > + */
> > > >
> > > > If we don't even use them, there's probably no need to call
> > > > vhost_dev_ioctl(). This may help to avoid confusion when we want to develop
> > > > new API for e.g dirty page tracking.
> > > Good point. It's better to reject these ioctls for now.
> > >
> > > PS. One thing I may need to clarify is that, we need the
> > > VHOST_SET_OWNER ioctl to get the vq->handle_kick to work.
> > > So if we don't call vhost_dev_ioctl(), we will need to
> > > call vhost_dev_set_owner() directly.
>
>
> I may miss something, it looks to me the there's no owner check in
> vhost_vring_ioctl() and the vhost_poll_start() can make sure handle_kick
> works?
Yeah, there is no owner check in vhost_vring_ioctl().
IIUC, vhost_poll_start() will start polling the file. And when
event arrives, vhost_poll_wakeup() will be called, and it will
queue work to work_list and wakeup worker to finish the work.
And the worker is created by vhost_dev_set_owner().
>
>
> > >
> > > >
> > > > > + r = vhost_dev_ioctl(&m->dev, cmd, argp);
> > > > > + 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 mdev_virtio_device_ops *ops = mdev_get_vhost_ops(mdev);
> > > > > + struct vhost_mdev *m;
> > > > > + int nvqs, r;
> > > > > +
> > > > > + /* Currently, we only accept the network devices. */
> > > > > + if (ops->get_device_id(mdev) != VIRTIO_ID_NET)
> > > > > + return -ENOTSUPP;
> > > > > +
> > > > > + m = devm_kzalloc(dev, sizeof(*m), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
> > > > > + if (!m)
> > > > > + return -ENOMEM;
> > > > > +
> > > > > + nvqs = VHOST_MDEV_VQ_MAX;
> > > >
> > > > On top. I think we probably need a better way other than hard-coded value
> > > > here.
> > > >
> > > > E.g we can read config and detect the max virtqueue supported based on
> > > > device id.
> > > Totally agree. We do need a better way than the hardcoded
> > > value in the future. For now, it might be better to keep
> > > it as is for simplicity before we have the MQ support.
>
>
> Yes, not for this patch for sure.
>
> Thanks
>
>
> > >
> > >
> > > > Thanks
> > > >
> > > >
> > > > > +
> > > > > + m->vqs = devm_kmalloc_array(dev, nvqs, sizeof(struct vhost_virtqueue),
> > > > > + GFP_KERNEL);
> > > > > + if (!m->vqs)
> > > > > + return -ENOMEM;
> > > > > +
> > > > > + mutex_init(&m->mutex);
> > > > > +
> > > > > + m->mdev = mdev;
> > > > > + m->nvqs = nvqs;
> > > > > + m->virtio_id = ops->get_device_id(mdev);
> > > > > +
> > > > > + r = vfio_add_group_dev(dev, &vfio_vhost_mdev_dev_ops, m);
> > > > > + if (r) {
> > > > > + mutex_destroy(&m->mutex);
> > > > > + return r;
> > > > > + }
> > > > > +
> > > > > + 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_AUTHOR("Intel Corporation");
> > > > > +MODULE_DESCRIPTION("Mediated device based accelerator for virtio");
> > > > > diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> > > > > index f3d75a60c2b5..8af7fb9e0149 100644
> > > > > --- a/include/linux/mdev.h
> > > > > +++ b/include/linux/mdev.h
> > > > > @@ -117,6 +117,10 @@ void mdev_set_virtio_ops(struct mdev_device *mdev,
> > > > > const struct mdev_virtio_device_ops *virtio_ops);
> > > > > const struct mdev_virtio_device_ops *
> > > > > mdev_get_virtio_ops(struct mdev_device *mdev);
> > > > > +void mdev_set_vhost_ops(struct mdev_device *mdev,
> > > > > + const struct mdev_virtio_device_ops *vhost_ops);
> > > > > +const struct mdev_virtio_device_ops *
> > > > > +mdev_get_vhost_ops(struct mdev_device *mdev);
> > > > > extern struct bus_type mdev_bus_type;
> > > > > @@ -133,6 +137,7 @@ 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..061a2824a1b3 100644
> > > > > --- a/include/uapi/linux/vhost.h
> > > > > +++ b/include/uapi/linux/vhost.h
> > > > > @@ -116,4 +116,22 @@
> > > > > #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 the device id. The device ids follow the same definition of
> > > > > + * the device id defined in virtio-spec. */
> > > > > +#define VHOST_MDEV_GET_DEVICE_ID _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 _IOR(VHOST_VIRTIO, 0x71, __u8)
> > > > > +#define VHOST_MDEV_SET_STATUS _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 _IOR(VHOST_VIRTIO, 0x73, struct vhost_mdev_config)
> > > > > +#define VHOST_MDEV_SET_CONFIG _IOW(VHOST_VIRTIO, 0x74, struct vhost_mdev_config)
> > > > > +/* Enable/disable the ring. */
> > > > > +#define VHOST_MDEV_SET_VRING_ENABLE _IOW(VHOST_VIRTIO, 0x75, struct vhost_vring_state)
> > > > > +/* Get the max ring size. */
> > > > > +#define VHOST_MDEV_GET_VRING_NUM _IOR(VHOST_VIRTIO, 0x76, __u16)
> > > > > +
> > > > > #endif
> > > > > diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_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 {
> > > > > unsigned short reserved;
> > > > > };
> > > > > +/* VHOST_MDEV specific definitions */
> > > > > +
> > > > > +struct vhost_mdev_config {
> > > > > + __u32 off;
> > > > > + __u32 len;
> > > > > + __u8 buf[0];
> > > > > +};
> > > > > +
> > > > > /* Feature bits */
> > > > > /* Log all write descriptors. Can be changed while device is active. */
> > > > > #define VHOST_F_LOG_ALL 26
>
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