mm: Add a pasid member to struct mm_struct

A PASID is shared by all threads in a process. So the logical place to
keep track of it is in the mm_struct. Both ARM and x86 would use this
PASID.

 [ bp: Massage commit message. ]

Suggested-by: Christoph Hellwig <[email protected]>
Signed-off-by: Fenghua Yu <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Tony Luck <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: Fenghua Yu

include/linux/mm_types.h

@@ -542,6 +542,10 @@ struct mm_struct {
 		atomic_long_t hugetlb_usage;
 #endif
 		struct work_struct async_put_work;
+
+#ifdef CONFIG_IOMMU_SUPPORT
+		u32 pasid;
+#endif
 	} __randomize_layout;
 
 	/*