[PATCH] mm/fork: Clear PASID for new mm

[Jean-Philippe Brucker]

From: Fenghua Yu <fenghua.yu@xxxxxxxxx>

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.

Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
---
This patch was part of the series introducing mm->pasid, but got lost
along the way [1]. It still makes sense to have it, because each address
space has a different PASID. And the IOMMU code in iommu_sva_alloc_pasid()
expects the pasid field of a new mm struct to be cleared.

[1] https://lore.kernel.org/linux-iommu/YDgh53AcQHT+T3L0@xxxxxxxxxxxxxxxxxxxxxxx/
---
 include/linux/mm_types.h | 1 +
 kernel/fork.c            | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0974ad501a47..6613b26a8894 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -23,6 +23,7 @@
 #endif
 #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))
 
+#define INIT_PASID	0
 
 struct address_space;
 struct mem_cgroup;
diff --git a/kernel/fork.c b/kernel/fork.c
index d66cd1014211..808af2cc8ab6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -994,6 +994,13 @@ 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
@@ -1024,6 +1031,7 @@ 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);
-- 
2.30.1