iommufd: Add IOMMU_DEVICE_GET_INFO

Under nested IOMMU translation, userspace owns the stage-1 translation
structure (e.g. the stage-1 page table of Intel VT-d or the context table
of ARM SMMUv3). Such stage-1 translation structures 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 structure to kernel.

This adds ioctl: IOMMU_DEVICE_GET_INFO to query the IOMMU hardware
capability for a given device.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>

drivers/iommu/iommufd/device.c

@@ -132,6 +132,83 @@ void iommufd_device_unbind(struct iommufd_device *idev)
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_device_unbind, 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 *)(ptr + index)))
+			return -EFAULT;
+	}
+	return 0;
+}
+
+int iommufd_device_get_info(struct iommufd_ucmd *ucmd)
+{
+	struct iommu_device_info *cmd = ucmd->cmd;
+	struct iommufd_object *dev_obj;
+	struct device *dev;
+	const struct iommu_ops *ops;
+	void *data;
+	unsigned int length, data_len;
+	int rc;
+
+	if (cmd->flags || cmd->__reserved || !cmd->data_len)
+		return -EOPNOTSUPP;
+
+	dev_obj = iommufd_get_object(ucmd->ictx, cmd->dev_id,
+				     IOMMUFD_OBJ_DEVICE);
+	if (IS_ERR(dev_obj))
+		return PTR_ERR(dev_obj);
+
+	dev = container_of(dev_obj, struct iommufd_device, obj)->dev;
+
+	ops = dev_iommu_ops(dev);
+	if (!ops || !ops->hw_info) {
+		rc = -EOPNOTSUPP;
+		goto out_put;
+	}
+
+	if (ops->driver_type == IOMMU_DEVICE_DATA_NONE) {
+		rc = -EOPNOTSUPP;
+		goto out_put;
+	}
+
+	data = ops->hw_info(dev, &data_len);
+	if (IS_ERR(data)) {
+		rc = PTR_ERR(data);
+		goto out_put;
+	}
+
+	length = min(cmd->data_len, data_len);
+	if (copy_to_user(u64_to_user_ptr(cmd->data_ptr), data, length)) {
+		rc = -EFAULT;
+		goto out_free_data;
+	}
+
+	/*
+	 * Zero the trailing bytes for userspace if the 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_free_data;
+	}
+
+	cmd->out_device_type = ops->driver_type;
+	cmd->data_len = data_len;
+
+	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
+
+out_free_data:
+	kfree(data);
+out_put:
+	iommufd_put_object(dev_obj);
+	return rc;
+}
+
 static int iommufd_device_setup_msi(struct iommufd_device *idev,
 				    struct iommufd_hw_pagetable *hwpt,
 				    phys_addr_t sw_msi_start)

drivers/iommu/iommufd/iommufd_private.h

@@ -9,6 +9,8 @@
 #include <linux/refcount.h>
 #include <linux/uaccess.h>
 
+#include "../iommu-priv.h"
+
 struct iommu_domain;
 struct iommu_group;
 struct iommu_option;
@@ -256,6 +258,7 @@ iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
 void iommufd_hw_pagetable_destroy(struct iommufd_object *obj);
 
 void iommufd_device_destroy(struct iommufd_object *obj);
+int iommufd_device_get_info(struct iommufd_ucmd *ucmd);
 
 struct iommufd_access {
 	struct iommufd_object obj;

drivers/iommu/iommufd/main.c

@@ -253,6 +253,7 @@ union ucmd_buffer {
 	struct iommu_ioas_alloc alloc;
 	struct iommu_ioas_allow_iovas allow_iovas;
 	struct iommu_ioas_iova_ranges iova_ranges;
+	struct iommu_device_info info;
 	struct iommu_ioas_map map;
 	struct iommu_ioas_unmap unmap;
 #ifdef CONFIG_IOMMUFD_TEST
@@ -286,6 +287,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
 		 src_iova),
 	IOCTL_OP(IOMMU_IOAS_IOVA_RANGES, iommufd_ioas_iova_ranges,
 		 struct iommu_ioas_iova_ranges, out_iova_alignment),
+	IOCTL_OP(IOMMU_DEVICE_GET_INFO, iommufd_device_get_info, struct iommu_device_info,
+		 __reserved),
 	IOCTL_OP(IOMMU_IOAS_MAP, iommufd_ioas_map, struct iommu_ioas_map,
 		 iova),
 	IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct iommu_ioas_unmap,

include/uapi/linux/iommufd.h

@@ -47,6 +47,7 @@ enum {
 	IOMMUFD_CMD_IOAS_UNMAP,
 	IOMMUFD_CMD_OPTION,
 	IOMMUFD_CMD_VFIO_IOAS,
+	IOMMUFD_CMD_DEVICE_GET_INFO,
 };
 
 /**
@@ -370,4 +371,40 @@ struct iommu_device_info_vtd {
 	__aligned_u64 cap_reg;
 	__aligned_u64 ecap_reg;
 };
+
+/**
+ * struct iommu_device_info - ioctl(IOMMU_DEVICE_GET_INFO)
+ * @size: sizeof(struct iommu_device_info)
+ * @flags: Must be 0
+ * @dev_id: The device being attached to the IOMMU
+ * @data_len: Input the type specific data buffer length in bytes
+ * @data_ptr: Pointer to the type specific structure (e.g.
+ *	      struct iommu_device_info_vtd)
+ * @out_data_type: Output the underlying iommu hardware type, it is one
+ *		   of enum iommu_device_data_type.
+ * @__reserved: Must be 0
+ *
+ * Query the hardware iommu capability for given device which has been
+ * bound to iommufd. @data_len is set to be the size of the buffer to
+ * 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
+ * vIOMMU and the hardware IOMMU, also for the availabillity checking of
+ * iommu hardware feature like dirty page tracking in IOMMU page table.
+ *
+ * The @out_device_type will be filled if the ioctl succeeds. It would
+ * be used in multiple iommufd operations like hw_pagetable allocation,
+ * iommu cache invalidation.
+ */
+struct iommu_device_info {
+	__u32 size;
+	__u32 flags;
+	__u32 dev_id;
+	__u32 data_len;
+	__aligned_u64 data_ptr;
+	__u32 out_device_type;
+	__u32 __reserved;
+};
+#define IOMMU_DEVICE_GET_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_DEVICE_GET_INFO)
 #endif