Re: [PATCH v12 18/24] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

Alex Williamson
2023-06-12T22:28:19Z

On Fri, 2 Jun 2023 05:16:47 -0700
Yi Liu <yi.l.liu@intel.com> wrote:

> This adds ioctl for userspace to bind device cdev fd to iommufd.
>
> VFIO_DEVICE_BIND_IOMMUFD: bind device to an iommufd, hence gain DMA
> control provided by the iommufd. open_device
> op is called after bind_iommufd op.
>
> Tested-by: Yanting Jiang <yanting.jiang@intel.com>
> Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Tested-by: Terrence Xu <terrence.xu@intel.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
> drivers/vfio/device_cdev.c | 123 +++++++++++++++++++++++++++++++++++++
> drivers/vfio/vfio.h | 13 ++++
> drivers/vfio/vfio_main.c | 5 ++
> include/linux/vfio.h | 3 +-
> include/uapi/linux/vfio.h | 27 ++++++++
> 5 files changed, 170 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
> index 1c640016a824..a4498ddbe774 100644
> --- a/drivers/vfio/device_cdev.c
> +++ b/drivers/vfio/device_cdev.c
> @@ -3,6 +3,7 @@
> * Copyright (c) 2023 Intel Corporation.
> */
> #include <linux/vfio.h>
> +#include <linux/iommufd.h>
>
> #include "vfio.h"
>
> @@ -44,6 +45,128 @@ int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep)
> return ret;
> }
>
> +static void vfio_device_get_kvm_safe(struct vfio_device_file *df)
> +{
> + spin_lock(&df->kvm_ref_lock);
> + if (df->kvm)
> + _vfio_device_get_kvm_safe(df->device, df->kvm);
> + spin_unlock(&df->kvm_ref_lock);
> +}
> +
> +void vfio_df_cdev_close(struct vfio_device_file *df)
> +{
> + struct vfio_device *device = df->device;
> +
> + /*
> + * In the time of close, there is no contention with another one
> + * changing this flag. So read df->access_granted without lock
> + * and no smp_load_acquire() is ok.
> + */
> + if (!df->access_granted)
> + return;
> +
> + mutex_lock(&device->dev_set->lock);
> + vfio_df_close(df);
> + vfio_device_put_kvm(device);
> + iommufd_ctx_put(df->iommufd);
> + device->cdev_opened = false;
> + mutex_unlock(&device->dev_set->lock);
> + vfio_device_unblock_group(device);
> +}
> +
> +static struct iommufd_ctx *vfio_get_iommufd_from_fd(int fd)
> +{
> + struct iommufd_ctx *iommufd;
> + struct fd f;
> +
> + f = fdget(fd);
> + if (!f.file)
> + return ERR_PTR(-EBADF);
> +
> + iommufd = iommufd_ctx_from_file(f.file);
> +
> + fdput(f);
> + return iommufd;
> +}
> +
> +long vfio_df_ioctl_bind_iommufd(struct vfio_device_file *df,
> + struct vfio_device_bind_iommufd __user *arg)
> +{
> + struct vfio_device *device = df->device;
> + struct vfio_device_bind_iommufd bind;
> + unsigned long minsz;
> + int ret;
> +
> + static_assert(__same_type(arg->out_devid, df->devid));
> +
> + minsz = offsetofend(struct vfio_device_bind_iommufd, out_devid);
> +
> + if (copy_from_user(&bind, arg, minsz))
> + return -EFAULT;
> +
> + if (bind.argsz < minsz || bind.flags || bind.iommufd < 0)
> + return -EINVAL;
> +
> + /* BIND_IOMMUFD only allowed for cdev fds */
> + if (df->group)
> + return -EINVAL;
> +
> + ret = vfio_device_block_group(device);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&device->dev_set->lock);
> + /* one device cannot be bound twice */
> + if (df->access_granted) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + df->iommufd = vfio_get_iommufd_from_fd(bind.iommufd);
> + if (IS_ERR(df->iommufd)) {
> + ret = PTR_ERR(df->iommufd);
> + df->iommufd = NULL;
> + goto out_unlock;
> + }
> +
> + /*
> + * Before the device open, get the KVM pointer currently
> + * associated with the device file (if there is) and obtain
> + * a reference. This reference is held until device closed.
> + * Save the pointer in the device for use by drivers.
> + */
> + vfio_device_get_kvm_safe(df);
> +
> + ret = vfio_df_open(df);
> + if (ret)
> + goto out_put_kvm;
> +
> + ret = copy_to_user(&arg->out_devid, &df->devid,
> + sizeof(df->devid)) ? -EFAULT : 0;
> + if (ret)
> + goto out_close_device;
> +
> + /*
> + * Paired with smp_load_acquire() in vfio_device_fops::ioctl/
> + * read/write/mmap
> + */
> + smp_store_release(&df->access_granted, true);
> + device->cdev_opened = true;
> + mutex_unlock(&device->dev_set->lock);
> + return 0;
> +
> +out_close_device:
> + vfio_df_close(df);
> +out_put_kvm:
> + vfio_device_put_kvm(device);
> + iommufd_ctx_put(df->iommufd);
> + df->iommufd = NULL;
> +out_unlock:
> + mutex_unlock(&device->dev_set->lock);
> + vfio_device_unblock_group(device);
> + return ret;
> +}
> +
> static char *vfio_device_devnode(const struct device *dev, umode_t *mode)
> {
> return kasprintf(GFP_KERNEL, "vfio/devices/%s", dev_name(dev));
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index d12b5b524bfc..42de40d2cd4d 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -287,6 +287,9 @@ static inline void vfio_device_del(struct vfio_device *device)
> }
>
> int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep);
> +void vfio_df_cdev_close(struct vfio_device_file *df);
> +long vfio_df_ioctl_bind_iommufd(struct vfio_device_file *df,
> + struct vfio_device_bind_iommufd __user *arg);
> int vfio_cdev_init(struct class *device_class);
> void vfio_cdev_cleanup(void);
> #else
> @@ -310,6 +313,16 @@ static inline int vfio_device_fops_cdev_open(struct inode *inode,
> return 0;
> }
>
> +static inline void vfio_df_cdev_close(struct vfio_device_file *df)
> +{
> +}
> +
> +static inline long vfio_df_ioctl_bind_iommufd(struct vfio_device_file *df,
> + struct vfio_device_bind_iommufd __user *arg)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> static inline int vfio_cdev_init(struct class *device_class)
> {
> return 0;
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index ef55af75f459..9ba4d420eda2 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -572,6 +572,8 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
>
> if (df->group)
> vfio_df_group_close(df);
> + else
> + vfio_df_cdev_close(df);
>
> vfio_device_put_registration(device);
>
> @@ -1145,6 +1147,9 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
> struct vfio_device *device = df->device;
> int ret;
>
> + if (cmd == VFIO_DEVICE_BIND_IOMMUFD)
> + return vfio_df_ioctl_bind_iommufd(df, (void __user *)arg);
> +
> /* Paired with smp_store_release() following vfio_df_open() */
> if (!smp_load_acquire(&df->access_granted))
> return -EINVAL;
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 83cc5dc28b7a..e80a8ac86e46 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -66,6 +66,7 @@ struct vfio_device {
> struct iommufd_device *iommufd_device;
> bool iommufd_attached;
> #endif
> + bool cdev_opened:1;

Perhaps a more strongly defined data type here as well and roll
iommufd_attached into the same bit field scheme.

> };
>
> /**
> @@ -170,7 +171,7 @@ vfio_iommufd_device_hot_reset_devid(struct vfio_device *vdev,
>
> static inline bool vfio_device_cdev_opened(struct vfio_device *device)
> {
> - return false;
> + return device->cdev_opened;
> }
>
> /**
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index f753124e1c82..7296012b7f36 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -194,6 +194,33 @@ struct vfio_group_status {
>
> /* --------------- IOCTLs for DEVICE file descriptors --------------- */
>
> +/*
> + * VFIO_DEVICE_BIND_IOMMUFD - _IOR(VFIO_TYPE, VFIO_BASE + 18,
> + * struct vfio_device_bind_iommufd)
> + * @argsz: User filled size of this data.
> + * @flags: Must be 0.
> + * @iommufd: iommufd to bind.
> + * @out_devid: The device id generated by this bind. devid is a handle for
> + * this device/iommufd bond and can be used in IOMMUFD commands.
> + *
> + * Bind a vfio_device to the specified iommufd.
> + *
> + * User is restricted from accessing the device before the binding operation
> + * is completed.
> + *
> + * Unbind is automatically conducted when device fd is closed.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +struct vfio_device_bind_iommufd {
> + __u32 argsz;
> + __u32 flags;
> + __s32 iommufd;
> + __u32 out_devid;
> +};
> +
> +#define VFIO_DEVICE_BIND_IOMMUFD _IO(VFIO_TYPE, VFIO_BASE + 18)
> +

Why are we still defining device ioctls 18-20 before existing device
ioctls? 18 should be defined after 17... Thanks,

Alex

> /**
> * VFIO_DEVICE_GET_INFO - _IOR(VFIO_TYPE, VFIO_BASE + 7,
> * struct vfio_device_info)