[PATCH v11 19/23] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

Yi Liu
2023-05-13T13:29:48Z

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>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/vfio/device_cdev.c | 130 +++++++++++++++++++++++++++++++++++++
drivers/vfio/vfio.h | 13 ++++
drivers/vfio/vfio_main.c | 5 ++
include/linux/vfio.h | 3 +-
include/uapi/linux/vfio.h | 28 ++++++++
5 files changed, 178 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
index 1c640016a824..291cc678a18b 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 +45,135 @@ 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_device_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_device_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_device_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;
+
+ if (vfio_device_is_noiommu(device) && !capable(CAP_SYS_RAWIO))
+ return -EPERM;
+
+ 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_device_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);
+
+ if (vfio_device_is_noiommu(device))
+ dev_warn(device->dev, "noiommu device is bound to iommufd by user "
+ "(%s:%d)\n", current->comm, task_pid_nr(current));
+ return 0;
+
+out_close_device:
+ vfio_device_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 6861f8ebb64d..8b359a7794be 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -279,6 +279,9 @@ static inline void vfio_device_del(struct vfio_device *device)

void vfio_init_device_cdev(struct vfio_device *device);
int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep);
+void vfio_device_cdev_close(struct vfio_device_file *df);
+long vfio_device_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
@@ -302,6 +305,16 @@ static inline int vfio_device_fops_cdev_open(struct inode *inode,
return 0;
}

+static inline void vfio_device_cdev_close(struct vfio_device_file *df)
+{
+}
+
+static inline long vfio_device_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 c87cc7afe92c..c9fa39ac4b02 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -574,6 +574,8 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)

if (df->group)
vfio_device_group_close(df);
+ else
+ vfio_device_cdev_close(df);

vfio_device_put_registration(device);

@@ -1147,6 +1149,9 @@ 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_device_ioctl_bind_iommufd(df, (void __user *)arg);
+
/* Paired with smp_store_release() following vfio_device_open() */
if (!smp_load_acquire(&df->access_granted))
return -EINVAL;
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 873275419f13..cf9d082a623c 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -67,6 +67,7 @@ struct vfio_device {
struct iommufd_device *iommufd_device;
bool iommufd_attached;
#endif
+ bool cdev_opened:1;
};

/**
@@ -169,7 +170,7 @@ vfio_iommufd_physical_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 24858b650562..07c917de31e9 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -194,6 +194,34 @@ struct vfio_group_status {

/* --------------- IOCTLs for DEVICE file descriptors --------------- */

+/*
+ * VFIO_DEVICE_BIND_IOMMUFD - _IOR(VFIO_TYPE, VFIO_BASE + 19,
+ * struct vfio_device_bind_iommufd)
+ *
+ * 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.
+ *
+ * @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.
+ *
+ * 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 + 19)
+
/**
* VFIO_DEVICE_GET_INFO - _IOR(VFIO_TYPE, VFIO_BASE + 7,
* struct vfio_device_info)
--
2.34.1