[PATCH v6 21/24] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

Yi Liu
2023-03-08T13:33:24Z

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@intel.com>
---
drivers/vfio/device_cdev.c | 166 +++++++++++++++++++++++++++++++++++++
drivers/vfio/group.c | 15 ++++
drivers/vfio/vfio.h | 15 ++++
drivers/vfio/vfio_main.c | 29 ++++++-
include/uapi/linux/vfio.h | 37 +++++++++
5 files changed, 258 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
index 1c640016a824..568cc9da16c7 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 +45,171 @@ 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;
+
+ /*
+ * As df->access_granted writer is under dev_set->lock as well,
+ * so this read no need to use smp_load_acquire() to pair with
+ * smp_store_release() in the caller of vfio_device_open().
+ */
+ if (!df->access_granted)
+ return;
+
+ mutex_lock(&device->dev_set->lock);
+ 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);
+}
+
+static int vfio_device_cdev_probe_noiommu(struct vfio_device *device)
+{
+ struct iommu_group *iommu_group;
+ int ret = 0;
+
+ if (!IS_ENABLED(CONFIG_VFIO_NOIOMMU) || !vfio_noiommu)
+ return -EINVAL;
+
+ if (!capable(CAP_SYS_RAWIO))
+ return -EPERM;
+
+ iommu_group = iommu_group_get(device->dev);
+ if (!iommu_group)
+ return 0;
+
+ /*
+ * We cannot support noiommu mode for devices that are protected
+ * by IOMMU. So check the iommu_group, if it is a no-iommu group
+ * created by VFIO, we support. If not, we refuse.
+ */
+ if (!vfio_group_find_noiommu_group_from_iommu(iommu_group))
+ ret = -EINVAL;
+ iommu_group_put(iommu_group);
+ return ret;
+}
+
+static struct iommufd_ctx *vfio_get_iommufd_from_fd(int fd)
+{
+ struct fd f;
+ struct iommufd_ctx *iommufd;
+
+ 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;
+ struct iommufd_ctx *iommufd = NULL;
+ unsigned long minsz;
+ int ret;
+
+ static_assert(__same_type(arg->out_devid, bind.out_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)
+ 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 got access, should fail it. */
+ if (df->access_granted) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ /* iommufd < 0 means noiommu mode */
+ if (bind.iommufd < 0) {
+ ret = vfio_device_cdev_probe_noiommu(device);
+ if (ret)
+ goto out_unlock;
+ } else {
+ iommufd = vfio_get_iommufd_from_fd(bind.iommufd);
+ if (IS_ERR(iommufd)) {
+ ret = PTR_ERR(iommufd);
+ 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);
+
+ df->iommufd = iommufd;
+ ret = vfio_device_open(df);
+ if (ret)
+ goto out_put_kvm;
+
+ if (df->iommufd)
+ bind.out_devid = df->devid;
+ else
+ bind.out_devid = IOMMUFD_INVALID_ID;
+
+ ret = copy_to_user(&arg->out_devid, &bind.out_devid,
+ sizeof(bind.out_devid)) ? -EFAULT : 0;
+ if (ret)
+ goto out_close_device;
+
+ if (bind.iommufd < 0)
+ dev_warn(device->dev, "device is bound to vfio-noiommu 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;
+ vfio_device_put_kvm(device);
+ if (iommufd)
+ iommufd_ctx_put(iommufd);
+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/group.c b/drivers/vfio/group.c
index 51c027134814..fc49f2459b1a 100644
--- a/drivers/vfio/group.c
+++ b/drivers/vfio/group.c
@@ -701,6 +701,21 @@ static struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
return group;
}

+struct vfio_group *
+vfio_group_find_noiommu_group_from_iommu(struct iommu_group *iommu_group)
+{
+ struct vfio_group *group;
+ bool found = false;
+
+ mutex_lock(&vfio.group_lock);
+ group = vfio_group_find_from_iommu(iommu_group);
+ if (group && group->type == VFIO_NO_IOMMU)
+ found = true;
+ mutex_unlock(&vfio.group_lock);
+
+ return found ? group : NULL;
+}
+
int vfio_device_set_group(struct vfio_device *device,
enum vfio_group_type type)
{
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index 3f359f04b754..5df737b24102 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -91,6 +91,8 @@ struct vfio_group {

int vfio_device_block_group(struct vfio_device *device);
void vfio_device_unblock_group(struct vfio_device *device);
+struct vfio_group *
+vfio_group_find_noiommu_group_from_iommu(struct iommu_group *iommu_group);
int vfio_device_set_group(struct vfio_device *device,
enum vfio_group_type type);
void vfio_device_remove_group(struct vfio_device *device);
@@ -273,6 +275,9 @@ 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
@@ -296,6 +301,16 @@ 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 b0c2a7544524..08bb1705d02d 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -575,6 +575,8 @@ 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);

@@ -1148,7 +1150,14 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
struct vfio_device *device = df->device;
int ret;

- /* Paired with smp_store_release() in vfio_device_group_open() */
+ if (cmd == VFIO_DEVICE_BIND_IOMMUFD)
+ return vfio_device_ioctl_bind_iommufd(df, (void __user *)arg);
+
+ /*
+ * Paired with smp_store_release() in the caller of
+ * vfio_device_open(). e.g. vfio_device_group_open()
+ * and vfio_device_ioctl_bind_iommufd()
+ */
if (!smp_load_acquire(&df->access_granted))
return -EINVAL;

@@ -1179,7 +1188,11 @@ static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf,
struct vfio_device_file *df = filep->private_data;
struct vfio_device *device = df->device;

- /* Paired with smp_store_release() in vfio_device_group_open() */
+ /*
+ * Paired with smp_store_release() in the caller of
+ * vfio_device_open(). e.g. vfio_device_group_open()
+ * and vfio_device_ioctl_bind_iommufd()
+ */
if (!smp_load_acquire(&df->access_granted))
return -EINVAL;

@@ -1196,7 +1209,11 @@ static ssize_t vfio_device_fops_write(struct file *filep,
struct vfio_device_file *df = filep->private_data;
struct vfio_device *device = df->device;

- /* Paired with smp_store_release() in vfio_device_group_open() */
+ /*
+ * Paired with smp_store_release() in the caller of
+ * vfio_device_open(). e.g. vfio_device_group_open()
+ * and vfio_device_ioctl_bind_iommufd()
+ */
if (!smp_load_acquire(&df->access_granted))
return -EINVAL;

@@ -1211,7 +1228,11 @@ static int vfio_device_fops_mmap(struct file *filep, struct vm_area_struct *vma)
struct vfio_device_file *df = filep->private_data;
struct vfio_device *device = df->device;

- /* Paired with smp_store_release() in vfio_device_group_open() */
+ /*
+ * Paired with smp_store_release() in the caller of
+ * vfio_device_open(). e.g. vfio_device_group_open()
+ * and vfio_device_ioctl_bind_iommufd()
+ */
if (!smp_load_acquire(&df->access_granted))
return -EINVAL;

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 382d95455f89..a53afe349a34 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -194,6 +194,43 @@ 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.
+ *
+ * The user should provide a device cookie when calling this ioctl. The
+ * cookie is carried only in event e.g. I/O fault reported to userspace
+ * via iommufd. The user should use devid returned by this ioctl to mark
+ * the target device in other ioctls (e.g. iommu hardware infomration query
+ * via iommufd, and etc.).
+ *
+ * User is not allowed to access 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: reserved for future extension.
+ * @dev_cookie: a per device cookie provided by userspace.
+ * @iommufd: iommufd to bind. a negative value means noiommu.
+ * @out_devid: the device id generated by this bind. This field is valid
+ * as long as the input @iommufd is valid. Otherwise, it is
+ * meaningless.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+struct vfio_device_bind_iommufd {
+ __u32 argsz;
+ __u32 flags;
+ __aligned_u64 dev_cookie;
+ __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