[PATCH v2 13/14] vfio: Add ioctls for device cdev using iommufd

Yi Liu
2023-02-06T09:07:26Z

This adds three vfio device ioctls for userspace using iommufd to set up
secure DMA context for device access.

VFIO_DEVICE_BIND_IOMMUFD: bind device to an iommufd, hence gain DMA
control provided by the iommufd. VFIO no
iommu mode is indicated by passing a minus
fd value.
VFIO_DEVICE_ATTACH_IOMMUFD_PT: attach device to IOAS, hw_pagetable
managed by iommufd. Attach can be
undo by VFIO_DEVICE_DETACH_IOMMUFD_PT
or device fd close.
VFIO_DEVICE_DETACH_IOMMUFD_PT: detach device from the current attached
IOAS or hw_pagetable managed by iommufd.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/vfio/device_cdev.c | 176 +++++++++++++++++++++++++++++++++++++
drivers/vfio/vfio.h | 33 ++++++-
drivers/vfio/vfio_main.c | 47 +++++++++-
include/linux/iommufd.h | 6 ++
include/uapi/linux/vfio.h | 86 ++++++++++++++++++
5 files changed, 343 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
index f024833c9e2c..4105cc939b7b 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"

@@ -46,6 +47,181 @@ int vfio_device_fops_open(struct inode *inode, struct file *filep)
return ret;
}

+void vfio_device_cdev_close(struct vfio_device_file *df)
+{
+ mutex_lock(&df->device->dev_set->lock);
+ vfio_device_close(df);
+ vfio_device_put_kvm(df->device);
+ mutex_unlock(&df->device->dev_set->lock);
+}
+
+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);
+}
+
+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;
+ struct fd f;
+ int ret;
+
+ minsz = offsetofend(struct vfio_device_bind_iommufd, iommufd);
+
+ 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;
+
+ 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 first 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 + minsz,
+ &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));
+ mutex_unlock(&device->dev_set->lock);
+ return 0;
+
+out_close_device:
+ vfio_device_close(df);
+out_put_kvm:
+ vfio_device_put_kvm(device);
+out_put_file:
+ if (iommufd)
+ fdput(f);
+out_unlock:
+ df->iommufd = NULL;
+ df->noiommu = false;
+ mutex_unlock(&device->dev_set->lock);
+ return ret;
+}
+
+int vfio_ioctl_device_attach(struct vfio_device_file *df,
+ void __user *arg)
+{
+ struct vfio_device *device = df->device;
+ struct vfio_device_attach_iommufd_pt attach;
+ int ret;
+
+ if (copy_from_user(&attach, (void __user *)arg, sizeof(attach)))
+ return -EFAULT;
+
+ if (attach.flags || attach.pt_id == IOMMUFD_INVALID_ID)
+ return -EINVAL;
+
+ if (!device->ops->bind_iommufd)
+ return -ENODEV;
+
+ mutex_lock(&device->dev_set->lock);
+ if (df->noiommu)
+ return -ENODEV;
+
+ ret = device->ops->attach_ioas(device, &attach.pt_id);
+ if (ret)
+ goto out_unlock;
+
+ ret = copy_to_user((void __user *)arg + offsetofend(
+ struct vfio_device_attach_iommufd_pt, flags),
+ &attach.pt_id,
+ sizeof(attach.pt_id)) ? -EFAULT : 0;
+ if (ret)
+ goto out_detach;
+ mutex_unlock(&device->dev_set->lock);
+ return 0;
+
+out_detach:
+ device->ops->detach_ioas(device);
+out_unlock:
+ mutex_unlock(&device->dev_set->lock);
+ return ret;
+}
+
+int vfio_ioctl_device_detach(struct vfio_device_file *df,
+ void __user *arg)
+{
+ struct vfio_device *device = df->device;
+ struct vfio_device_detach_iommufd_pt detach;
+
+ if (copy_from_user(&detach, (void __user *)arg, sizeof(detach)))
+ return -EFAULT;
+
+ if (detach.flags)
+ return -EINVAL;
+
+ if (!device->ops->bind_iommufd)
+ return -ENODEV;
+
+ mutex_lock(&device->dev_set->lock);
+ if (df->noiommu)
+ return -ENODEV;
+ device->ops->detach_ioas(device);
+ mutex_unlock(&device->dev_set->lock);
+ return 0;
+}
+
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 c7c75865afec..8a290c1455e1 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);
@@ -253,6 +255,13 @@ static inline void vfio_iommufd_unbind(struct vfio_device *device)
#if IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV)
void vfio_init_device_cdev(struct vfio_device *device);
int vfio_device_fops_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_ioctl_device_attach(struct vfio_device_file *df,
+ void __user *arg);
+int vfio_ioctl_device_detach(struct vfio_device_file *df,
+ void __user *arg);
int vfio_cdev_init(struct class *device_class);
void vfio_cdev_cleanup(void);
#else
@@ -266,6 +275,28 @@ static inline int vfio_device_fops_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_ioctl_device_attach(struct vfio_device_file *df,
+ void __user *arg)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int vfio_ioctl_device_detach(struct vfio_device_file *df,
+ void __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 035730dc6ad4..8559c3dfb335 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"
@@ -442,16 +443,41 @@ 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);

+ /* df->iommufd and df->noiommu should be exclusive */
+ if (WARN_ON(iommufd && df->noiommu))
+ return -EINVAL;
+
if (!try_module_get(device->dev->driver->owner))
return -ENODEV;

+ /*
+ * For group path, iommufd pointer is NULL when comes into this
+ * helper. Its noiommu support is in container.c.
+ *
+ * For iommufd compat mode, iommufd pointer here is a valid value.
+ * Its noiommu support is supposed to be 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. The reason is
+ * that userspace uses iommufd==-1 to indicate noiommu mode in this
+ * path. So caller of this helper will pass in a NULL iommufd
+ * pointer. To differentiate it from the group path which also
+ * passes NULL iommufd pointer in, df->noiommu is used. For cdev
+ * noiommu, df->noiommu would be set to mark noiommu case for cdev
+ * path.
+ *
+ * So if df->noiommu is set then this helper just goes ahead to
+ * open device. If not, it depends on if iommufd pointer is NULL
+ * to handle the group path, iommufd compat mode, normal cases in
+ * the cdev path.
+ */
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;
@@ -466,7 +492,7 @@ 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);
@@ -484,7 +510,7 @@ 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);
}
@@ -588,6 +614,8 @@ 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);

@@ -1162,6 +1190,9 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
bool access;
int ret;

+ if (cmd == VFIO_DEVICE_BIND_IOMMUFD)
+ return vfio_device_ioctl_bind_iommufd(df, arg);
+
/* Paired with smp_store_release() in vfio_device_open() */
access = smp_load_acquire(&df->access_granted);
if (!access)
@@ -1176,6 +1207,14 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
ret = vfio_ioctl_device_feature(device, (void __user *)arg);
break;

+ case VFIO_DEVICE_ATTACH_IOMMUFD_PT:
+ ret = vfio_ioctl_device_attach(df, (void __user *)arg);
+ break;
+
+ case VFIO_DEVICE_DETACH_IOMMUFD_PT:
+ ret = vfio_ioctl_device_detach(df, (void __user *)arg);
+ break;
+
default:
if (unlikely(!device->ops->ioctl))
ret = -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 23105eb036fa..c86cfe442884 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -190,6 +190,92 @@ 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. iommufd < 0 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_ATTACH_IOMMUFD_PT - _IOW(VFIO_TYPE, VFIO_BASE + 20,
+ * struct vfio_device_attach_iommufd_pt)
+ *
+ * Attach a vfio device to an iommufd address space specified by IOAS
+ * id or hw_pagetable (hwpt) id.
+ *
+ * Available only after a device has been bound to iommufd via
+ * VFIO_DEVICE_BIND_IOMMUFD
+ *
+ * Undo by VFIO_DEVICE_DETACH_IOMMUFD_PT or device fd close.
+ *
+ * @argsz: user filled size of this data.
+ * @flags: must be 0.
+ * @pt_id: Input the target id which can represent an ioas or a hwpt
+ * allocated via iommufd subsystem.
+ * Output the attached hwpt id which could be the specified
+ * hwpt itself or a hwpt automatically created for the
+ * specified ioas by kernel during the attachment.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+struct vfio_device_attach_iommufd_pt {
+ __u32 argsz;
+ __u32 flags;
+ __u32 pt_id;
+};
+
+#define VFIO_DEVICE_ATTACH_IOMMUFD_PT _IO(VFIO_TYPE, VFIO_BASE + 20)
+
+/*
+ * VFIO_DEVICE_DETACH_IOMMUFD_PT - _IOW(VFIO_TYPE, VFIO_BASE + 21,
+ * struct vfio_device_detach_iommufd_pt)
+ *
+ * Detach a vfio device from the iommufd address space it has been
+ * attached to. After it, device should be in a blocking DMA state.
+ *
+ * Available only after a device has been bound to iommufd via
+ * VFIO_DEVICE_BIND_IOMMUFD
+ *
+ * @argsz: user filled size of this data.
+ * @flags: must be 0.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+struct vfio_device_detach_iommufd_pt {
+ __u32 argsz;
+ __u32 flags;
+};
+
+#define VFIO_DEVICE_DETACH_IOMMUFD_PT _IO(VFIO_TYPE, VFIO_BASE + 21)
+
/**
* VFIO_DEVICE_GET_INFO - _IOR(VFIO_TYPE, VFIO_BASE + 7,
* struct vfio_device_info)
--
2.34.1