On Mon, Feb 20, 2023 at 07:48:09PM -0800, Yi Liu 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.
> VFIO no iommu mode is indicated by passing
> a negative iommufd value.
>
> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> ---
> drivers/vfio/device_cdev.c | 137 +++++++++++++++++++++++++++++++++++++
> drivers/vfio/vfio.h | 17 ++++-
> drivers/vfio/vfio_main.c | 30 ++++++--
> include/linux/iommufd.h | 6 ++
> include/uapi/linux/vfio.h | 34 +++++++++
> 5 files changed, 219 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
> index 9e2c1ecaaf4f..be62f0a5687e 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"
>
> @@ -45,6 +46,142 @@ 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)
> + goto unlock;
> +
> + _vfio_device_get_kvm_safe(df->device, df->kvm);
> +
> +unlock:
> + spin_unlock(&df->kvm_ref_lock);
> +}
> +
> +void vfio_device_cdev_close(struct vfio_device_file *df)
> +{
> + struct vfio_device *device = df->device;
> +
> + mutex_lock(&device->dev_set->lock);
> + if (!smp_load_acquire(&df->access_granted)) {
> + mutex_unlock(&device->dev_set->lock);
> + return;
> + }
> + vfio_device_close(df);
> + vfio_device_put_kvm(device);
> + if (df->iommufd)
> + iommufd_ctx_put(df->iommufd);
> + mutex_unlock(&device->dev_set->lock);
> + vfio_device_unblock_group(device);
> +}
> +
> +long vfio_device_ioctl_bind_iommufd(struct vfio_device_file *df,
> + unsigned long arg)
> +{
> + struct vfio_device *device = df->device;
> + struct vfio_device_bind_iommufd bind;
> + struct iommufd_ctx *iommufd = NULL;
> + struct fd f;
> + unsigned long minsz;
> + int ret;
> +
> + minsz = offsetofend(struct vfio_device_bind_iommufd, out_devid);
> +
> + if (copy_from_user(&bind, (void __user *)arg, minsz))
> + return -EFAULT;
> +
> + if (bind.argsz < minsz || bind.flags)
> + return -EINVAL;
> +
> + if (!device->ops->bind_iommufd)
> + return -ENODEV;
> +
> + ret = vfio_device_block_group(device);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&device->dev_set->lock);
> + /*
> + * If already been bound to an iommufd, or already set noiommu
> + * then fail it.
> + */
> + if (df->iommufd || df->noiommu) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + /* iommufd < 0 means noiommu mode */
> + if (bind.iommufd < 0) {
> + if (!capable(CAP_SYS_RAWIO)) {
> + ret = -EPERM;
> + goto out_unlock;
> + }
> + df->noiommu = true;
> + } else {
> + f = fdget(bind.iommufd);
> + if (!f.file) {
> + ret = -EBADF;
> + goto out_unlock;
> + }
> + iommufd = iommufd_ctx_from_file(f.file);
> + if (IS_ERR(iommufd)) {
> + ret = PTR_ERR(iommufd);
> + goto out_put_file;
> + }
> + }
> +
> + /*
> + * 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);
> +
> + df->iommufd = iommufd;
> + ret = vfio_device_open(df, &bind.out_devid, NULL);
> + if (ret)
> + goto out_put_kvm;
> +
> + ret = copy_to_user((void __user *)arg +
> + offsetofend(struct vfio_device_bind_iommufd, iommufd),
> + &bind.out_devid,
> + sizeof(bind.out_devid)) ? -EFAULT : 0;
> + if (ret)
> + goto out_close_device;
> +
> + if (iommufd)
> + fdput(f);
> + else if (df->noiommu)
> + dev_warn(device->dev, "vfio-noiommu device used by user "
> + "(%s:%d)\n", current->comm, task_pid_nr(current));
> +
> + /*
> + * Paired with smp_load_acquire() in vfio_device_fops::ioctl/
> + * read/write/mmap
> + */
> + smp_store_release(&df->access_granted, true);
> + mutex_unlock(&device->dev_set->lock);
> +
> + return 0;
> +
> +out_close_device:
> + vfio_device_close(df);
> +out_put_kvm:
> + df->iommufd = NULL;
> + df->noiommu = false;
> + vfio_device_put_kvm(device);
> +out_put_file:
> + if (iommufd) {
> + iommufd_ctx_put(iommufd);
> + fdput(f);
even if iommufd is NULL, still need to fdput(f) if f.file is true, right?
> + }
> +out_unlock:
> + mutex_unlock(&device->dev_set->lock);
> + vfio_device_unblock_group(device);
> + return ret;
> +}
> +
