[PATCH v4 02/17] iommu: Add nested domain support

[Yi Liu]

From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Introduce a new domain type for a user I/O page table, which is nested on
top of another user space address represented by a UNMANAGED domain. The
mappings of a nested domain are managed by user space software, so it is
not necessary to have map/unmap callbacks. But the updates of the PTEs in
the nested page table will be propagated to the hardware caches on both
IOMMU (IOTLB) and devices (DevTLB/ATC).

A nested domain is allocated by the domain_alloc_user op, and attached to
a device through the existing iommu_attach_device/group() interfaces.

Add a new domain op cache_invalidate_user for the userspace to flush the
hardware caches for a nested domain through iommufd. No wrapper for it,
as it's only supposed to be used by iommufd.

Pass in invalidation requests to the cache_invalidate_user op, in form of
a user data array that conatins a number of invalidation entries. Add an
iommu_user_data_array struct and an iommu_copy_user_data_from_array helper
for iommu drivers to walk through the invalidation request array and fetch
the data entry inside.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Co-developed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
 include/linux/iommu.h | 59 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 12e12e5563e6..439e295c91a3 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -66,6 +66,9 @@ struct iommu_domain_geometry {
 
 #define __IOMMU_DOMAIN_SVA	(1U << 4)  /* Shared process address space */
 
+#define __IOMMU_DOMAIN_NESTED	(1U << 5)  /* User-managed address space nested
+					      on a stage-2 translation        */
+
 #define IOMMU_DOMAIN_ALLOC_FLAGS ~__IOMMU_DOMAIN_DMA_FQ
 /*
  * This are the possible domain-types
@@ -92,6 +95,7 @@ struct iommu_domain_geometry {
 				 __IOMMU_DOMAIN_DMA_API |	\
 				 __IOMMU_DOMAIN_DMA_FQ)
 #define IOMMU_DOMAIN_SVA	(__IOMMU_DOMAIN_SVA)
+#define IOMMU_DOMAIN_NESTED	(__IOMMU_DOMAIN_NESTED)
 
 struct iommu_domain {
 	unsigned type;
@@ -241,6 +245,21 @@ struct iommu_user_data {
 	size_t len;
 };
 
+/**
+ * struct iommu_user_data_array - iommu driver specific user space data array
+ * @uptr: Pointer to the user buffer array for copy_from_user()
+ * @entry_len: The fixed-width length of a entry in the array, in bytes
+ * @entry_num: The number of total entries in the array
+ *
+ * A array having a @entry_num number of @entry_len sized entries, each entry is
+ * user space data, i.e. an uAPI that is defined in include/uapi/linux/iommufd.h
+ */
+struct iommu_user_data_array {
+	void __user *uptr;
+	size_t entry_len;
+	int entry_num;
+};
+
 /**
  * iommu_copy_user_data - Copy iommu driver specific user space data
  * @dst_data: Pointer to an iommu driver specific user data that is defined in
@@ -263,6 +282,34 @@ static inline int iommu_copy_user_data(void *dst_data,
 				     src_data->uptr, src_data->len);
 }
 
+/**
+ * iommu_copy_user_data_from_array - Copy iommu driver specific user space data
+ *                                   from an iommu_user_data_array input
+ * @dst_data: Pointer to an iommu driver specific user data that is defined in
+ *            include/uapi/linux/iommufd.h
+ * @src_data: Pointer to a struct iommu_user_data_array for user space data array
+ * @index: Index to offset the location in the array to copy user data from
+ * @data_len: Length of current user data structure, i.e. sizeof(struct _dst)
+ * @min_len: Initial length of user data structure for backward compatibility.
+ *           This should be offsetofend using the last member in the user data
+ *           struct that was initially added to include/uapi/linux/iommufd.h
+ */
+static inline int
+iommu_copy_user_data_from_array(void *dst_data,
+				const struct iommu_user_data_array *src_array,
+				int index, size_t data_len, size_t min_len)
+{
+	struct iommu_user_data src_data;
+
+	if (WARN_ON(!src_array || index >= src_array->entry_num))
+		return -EINVAL;
+	if (!src_array->entry_num)
+		return -EINVAL;
+	src_data.uptr = src_array->uptr + src_array->entry_len * index;
+	src_data.len = src_array->entry_len;
+	return iommu_copy_user_data(dst_data, &src_data, data_len, min_len);
+}
+
 /**
  * struct iommu_ops - iommu ops and capabilities
  * @capable: check capability
@@ -374,6 +421,15 @@ struct iommu_ops {
  * @iotlb_sync_map: Sync mappings created recently using @map to the hardware
  * @iotlb_sync: Flush all queued ranges from the hardware TLBs and empty flush
  *            queue
+ * @cache_invalidate_user: Flush hardware cache for user space IO page table.
+ *                         The @domain must be IOMMU_DOMAIN_NESTED. The @array
+ *                         passes in the cache invalidation requests, in form
+ *                         of a driver data structure. The driver must update
+ *                         array->entry_num to report the number of handled
+ *                         invalidation requests. The 32-bit @error_code can
+ *                         forward a driver specific error code to user space.
+ *                         Both the driver data structure and the error code
+ *                         must be defined in  include/uapi/linux/iommufd.h
  * @iova_to_phys: translate iova to physical address
  * @enforce_cache_coherency: Prevent any kind of DMA from bypassing IOMMU_CACHE,
  *                           including no-snoop TLPs on PCIe or other platform
@@ -403,6 +459,9 @@ struct iommu_domain_ops {
 			       size_t size);
 	void (*iotlb_sync)(struct iommu_domain *domain,
 			   struct iommu_iotlb_gather *iotlb_gather);
+	int (*cache_invalidate_user)(struct iommu_domain *domain,
+				     struct iommu_user_data_array *array,
+				     u32 *error_code);
 
 	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain,
 				    dma_addr_t iova);
-- 
2.34.1