[PATCH v3 3/4] iommufd: Add IOMMU_DEVICE_GET_HW_INFO

Yi Liu
2023-05-11T14:32:29Z

Under nested IOMMU translation, userspace owns the stage-1 translation
table (e.g. the stage-1 page table of Intel VT-d or the context table
of ARM SMMUv3, and etc.). Stage-1 translation tables are vendor specific,
and needs to be compatiable with the underlying IOMMU hardware. Hence,
userspace should know the IOMMU hardware capability before creating and
configuring the stage-1 translation table to kernel.

This adds IOMMU_DEVICE_GET_HW_INFO to query the IOMMU hardware information
for a given device. The returned data is vendor specific, userspace needs
to decode it with the structure mapped by the @out_data_type field.

As only physical devices have IOMMU hardware, so this will return error
if the given device is not a physical device.

Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/iommu/iommufd/device.c | 72 +++++++++++++++++++++++++
drivers/iommu/iommufd/iommufd_private.h | 1 +
drivers/iommu/iommufd/main.c | 3 ++
include/uapi/linux/iommufd.h | 37 +++++++++++++
4 files changed, 113 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 051bd8e99858..bc99d092de8f 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -263,6 +263,78 @@ u32 iommufd_device_to_id(struct iommufd_device *idev)
}
EXPORT_SYMBOL_NS_GPL(iommufd_device_to_id, IOMMUFD);

+static int iommufd_zero_fill_user(u64 ptr, int bytes)
+{
+ int index = 0;
+
+ for (; index < bytes; index++) {
+ if (put_user(0, (uint8_t __user *)u64_to_user_ptr(ptr + index)))
+ return -EFAULT;
+ }
+ return 0;
+}
+
+int iommufd_device_get_hw_info(struct iommufd_ucmd *ucmd)
+{
+ struct iommu_hw_info *cmd = ucmd->cmd;
+ unsigned int length = 0, data_len;
+ struct iommufd_device *idev;
+ const struct iommu_ops *ops;
+ void *data = NULL;
+ int rc = 0;
+
+ if (cmd->flags || cmd->__reserved || !cmd->data_len)
+ return -EOPNOTSUPP;
+
+ idev = iommufd_get_device(ucmd, cmd->dev_id);
+ if (IS_ERR(idev))
+ return PTR_ERR(idev);
+
+ ops = dev_iommu_ops(idev->dev);
+ if (!ops->hw_info)
+ goto done;
+
+ /* driver has hw_info callback should have a unique hw_info_type */
+ if (ops->hw_info_type == IOMMU_HW_INFO_TYPE_NONE) {
+ pr_warn_ratelimited("iommu driver set an invalid type\n");
+ rc = -ENODEV;
+ goto out_err;
+ }
+
+ data = ops->hw_info(idev->dev, &data_len);
+ if (IS_ERR(data)) {
+ rc = PTR_ERR(data);
+ goto out_err;
+ }
+
+ length = min(cmd->data_len, data_len);
+ if (copy_to_user(u64_to_user_ptr(cmd->data_ptr), data, length)) {
+ rc = -EFAULT;
+ goto out_err;
+ }
+
+ /*
+ * Zero the trailing bytes if the user buffer is bigger than the
+ * data size kernel actually has.
+ */
+ if (length < cmd->data_len) {
+ rc = iommufd_zero_fill_user(cmd->data_ptr + length,
+ cmd->data_len - length);
+ if (rc)
+ goto out_err;
+ }
+
+done:
+ cmd->data_len = length;
+ cmd->out_data_type = ops->hw_info_type;
+ rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
+
+out_err:
+ kfree(data);
+ iommufd_put_object(&idev->obj);
+ return rc;
+}
+
static int iommufd_group_setup_msi(struct iommufd_group *igroup,
struct iommufd_hw_pagetable *hwpt)
{
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index dba730129b8c..69d6bb61d387 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -308,6 +308,7 @@ iommufd_get_device(struct iommufd_ucmd *ucmd, u32 id)
}

void iommufd_device_destroy(struct iommufd_object *obj);
+int iommufd_device_get_hw_info(struct iommufd_ucmd *ucmd);

struct iommufd_access {
struct iommufd_object obj;
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 3932fe26522b..5c24e8971f09 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -269,6 +269,7 @@ static int iommufd_option(struct iommufd_ucmd *ucmd)
union ucmd_buffer {
struct iommu_destroy destroy;
struct iommu_hwpt_alloc hwpt;
+ struct iommu_hw_info info;
struct iommu_ioas_alloc alloc;
struct iommu_ioas_allow_iovas allow_iovas;
struct iommu_ioas_copy ioas_copy;
@@ -302,6 +303,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id),
IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc,
__reserved),
+ IOCTL_OP(IOMMU_DEVICE_GET_HW_INFO, iommufd_device_get_hw_info,
+ struct iommu_hw_info, __reserved),
IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
struct iommu_ioas_alloc, out_ioas_id),
IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 99bf0715f545..e9d42838dcbd 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -46,6 +46,7 @@ enum {
IOMMUFD_CMD_OPTION,
IOMMUFD_CMD_VFIO_IOAS,
IOMMUFD_CMD_HWPT_ALLOC,
+ IOMMUFD_CMD_DEVICE_GET_HW_INFO,
};

/**
@@ -377,4 +378,40 @@ struct iommu_hwpt_alloc {
enum iommu_hw_info_type {
IOMMU_HW_INFO_TYPE_NONE,
};
+
+/**
+ * struct iommu_hw_info - ioctl(IOMMU_DEVICE_GET_HW_INFO)
+ * @size: sizeof(struct iommu_hw_info)
+ * @flags: Must be 0
+ * @dev_id: The device bound to the iommufd
+ * @data_len: Input the length of the user buffer in bytes. Output the
+ * length of data filled in the user buffer.
+ * @data_ptr: Pointer to the user buffer
+ * @out_data_type: Output the iommu hardware info type as defined by
+ * enum iommu_hw_info_type.
+ * @__reserved: Must be 0
+ *
+ * Query the hardware iommu information for given device which has been
+ * bound to iommufd. @data_len is the size of the buffer which captures
+ * iommu type specific data and the data will be filled. Trailing bytes
+ * are zeroed if the user buffer is larger than the data kernel has.
+ *
+ * The type specific data would be used to sync capability between the
+ * virtual IOMMU and the hardware IOMMU. e.g. nested translation requires
+ * to check the hardware IOMMU capability so guest stage-1 page table
+ * uses a format compatible to the hardware IOMMU.
+ *
+ * The @out_data_type will be filled if the ioctl succeeds. It would
+ * be used to decode the data filled in the buffer pointed by @data_ptr.
+ */
+struct iommu_hw_info {
+ __u32 size;
+ __u32 flags;
+ __u32 dev_id;
+ __u32 data_len;
+ __aligned_u64 data_ptr;
+ __u32 out_data_type;
+ __u32 __reserved;
+};
+#define IOMMU_DEVICE_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_DEVICE_GET_HW_INFO)
#endif
--
2.34.1