[PATCH v5 16/19] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

Yi Liu
2023-02-27T11:12:25Z

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 | 146 +++++++++++++++++++++++++++++++++++++
drivers/vfio/vfio.h | 17 ++++-
drivers/vfio/vfio_main.c | 54 ++++++++++++--
include/linux/iommufd.h | 6 ++
include/uapi/linux/vfio.h | 34 +++++++++
5 files changed, 248 insertions(+), 9 deletions(-)

diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
index 9e2c1ecaaf4f..37f80e368551 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 +46,151 @@ 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);
+ /*
+ * 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) {
+ 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);
+}
+
+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,
+ unsigned long arg)
+{
+ struct vfio_device *device = df->device;
+ struct vfio_device_bind_iommufd bind;
+ struct iommufd_ctx *iommufd = NULL;
+ 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 {
+ 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, &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 (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);
+ 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/vfio.h b/drivers/vfio/vfio.h
index 8661de75f94b..4716a904e63b 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -23,7 +23,9 @@ struct vfio_device_file {
bool access_granted;
spinlock_t kvm_ref_lock; /* protect kvm field */
struct kvm *kvm;
- struct iommufd_ctx *iommufd; /* protected by struct vfio_device_set::lock */
+ /* protected by struct vfio_device_set::lock */
+ struct iommufd_ctx *iommufd;
+ bool noiommu;
};

void vfio_device_put_registration(struct vfio_device *device);
@@ -269,6 +271,9 @@ 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,
+ unsigned long arg);
int vfio_cdev_init(struct class *device_class);
void vfio_cdev_cleanup(void);
#else
@@ -292,6 +297,16 @@ 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,
+ unsigned long 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 3f83447d022e..69d0add930bb 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -37,6 +37,7 @@
#include <linux/interval_tree.h>
#include <linux/iova_bitmap.h>
#include <linux/iommufd.h>
+#include <uapi/linux/iommufd.h>
#include "vfio.h"

#define DRIVER_VERSION "0.3"
@@ -422,16 +423,32 @@ static int vfio_device_first_open(struct vfio_device_file *df,
{
struct vfio_device *device = df->device;
struct iommufd_ctx *iommufd = df->iommufd;
- int ret;
+ int ret = 0;

lockdep_assert_held(&device->dev_set->lock);

+ if (WARN_ON(iommufd && df->noiommu))
+ return -EINVAL;
+
if (!try_module_get(device->dev->driver->owner))
return -ENODEV;

+ /*
+ * For group/container path, iommufd pointer is NULL when comes
+ * into this helper. Its noiommu support is handled by
+ * vfio_device_group_use_iommu()
+ *
+ * For iommufd compat mode, iommufd pointer here is a valid value.
+ * Its noiommu support is in vfio_iommufd_bind().
+ *
+ * For device cdev path, iommufd pointer here is a valid value for
+ * normal cases, but it is NULL if it's noiommu. Check df->noiommu
+ * to differentiate cdev noiommu from the group/container path which
+ * also passes NULL iommufd pointer in. If set then do nothing.
+ */
if (iommufd)
ret = vfio_iommufd_bind(device, iommufd, dev_id, pt_id);
- else
+ else if (!df->noiommu)
ret = vfio_device_group_use_iommu(device);
if (ret)
goto err_module_put;
@@ -446,7 +463,7 @@ static int vfio_device_first_open(struct vfio_device_file *df,
err_unuse_iommu:
if (iommufd)
vfio_iommufd_unbind(device);
- else
+ else if (!df->noiommu)
vfio_device_group_unuse_iommu(device);
err_module_put:
module_put(device->dev->driver->owner);
@@ -464,7 +481,7 @@ static void vfio_device_last_close(struct vfio_device_file *df)
device->ops->close_device(device);
if (iommufd)
vfio_iommufd_unbind(device);
- else
+ else if (!df->noiommu)
vfio_device_group_unuse_iommu(device);
module_put(device->dev->driver->owner);
}
@@ -549,6 +566,8 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)

if (!df->is_cdev_device)
vfio_device_group_close(df);
+ else
+ vfio_device_cdev_close(df);

vfio_device_put_registration(device);

@@ -1122,7 +1141,14 @@ 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, 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;

@@ -1153,7 +1179,11 @@ 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;

@@ -1170,7 +1200,11 @@ 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;

@@ -1185,7 +1219,11 @@ 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/linux/iommufd.h b/include/linux/iommufd.h
index 650d45629647..9672cf839687 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -17,6 +17,12 @@ struct iommufd_ctx;
struct iommufd_access;
struct file;

+/*
+ * iommufd core init xarray with flags==XA_FLAGS_ALLOC1, so valid
+ * ID starts from 1.
+ */
+#define IOMMUFD_INVALID_ID 0
+
struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
struct device *dev, u32 *id);
void iommufd_device_unbind(struct iommufd_device *idev);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 4bf11ee8de53..92aa8dbc970a 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -194,6 +194,40 @@ 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. capability query via iommufd).
+ *
+ * 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.
+ *
+ * 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