[PATCH v4 08/12] fork: Clear PASID for new mm

[Fenghua Yu]

When a new mm is created, its PASID should be cleared, i.e. the PASID is
initialized to its init state 0 on both ARM and X86.

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
v2:
- Add this patch to initialize PASID value for a new mm.

 include/linux/mm_types.h | 2 ++
 kernel/fork.c            | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index d61285cfe027..d60d2ec10881 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -22,6 +22,8 @@
 #endif
 #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))
 
+/* Initial PASID value is 0. */
+#define INIT_PASID	0
 
 struct address_space;
 struct mem_cgroup;
diff --git a/kernel/fork.c b/kernel/fork.c
index 142b23645d82..43b5f112604d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1007,6 +1007,13 @@ static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 #endif
 }
 
+static void mm_init_pasid(struct mm_struct *mm)
+{
+#ifdef CONFIG_IOMMU_SUPPORT
+	mm->pasid = INIT_PASID;
+#endif
+}
+
 static void mm_init_uprobes_state(struct mm_struct *mm)
 {
 #ifdef CONFIG_UPROBES
@@ -1035,6 +1042,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 	mm_init_cpumask(mm);
 	mm_init_aio(mm);
 	mm_init_owner(mm, p);
+	mm_init_pasid(mm);
 	RCU_INIT_POINTER(mm->exe_file, NULL);
 	mmu_notifier_subscriptions_init(mm);
 	init_tlb_flush_pending(mm);
-- 
2.19.1