kernel/fork: Initialize mm's PASID

A new mm doesn't have a PASID yet when it's created. Initialize the mm's PASID on fork() or for init_mm to INVALID_IOASID (-1). INIT_PASID (0) is reserved for kernel legacy DMA PASID. It cannot be allocated to a user process. Initializing the process's PASID to 0 may cause confusion that's why the process uses the reserved kernel legacy DMA PASID. Initializing the PASID to INVALID_IOASID (-1) explicitly tells the process doesn't have a valid PASID yet. Even though the only user of mm_pasid_init() is in fork.c, define it in <linux/sched/mm.h> as the first of three mm/pasid life cycle functions (init/set/drop) to keep these all together. Suggested-by: Dave Hansen <[email protected]> Signed-off-by: Fenghua Yu <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Reviewed-by: Tony Luck <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Link: https://lore.kernel.org/r/[email protected]
SocioProphet · Feb 14, 2022 · a6cbd44 · a6cbd44
1 parent 7a5fbc9
commit a6cbd44
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Showing 3 changed files with 16 additions and 8 deletions.
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
@@ -8,6 +8,7 @@
 #include <linux/mm_types.h>
 #include <linux/gfp.h>
 #include <linux/sync_core.h>
+#include <linux/ioasid.h>
 
 /*
  * Routines for handling mm_structs
@@ -433,4 +434,13 @@ static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
 }
 #endif
 
+#ifdef CONFIG_IOMMU_SVA
+static inline void mm_pasid_init(struct mm_struct *mm)
+{
+	mm->pasid = INVALID_IOASID;
+}
+#else
+static inline void mm_pasid_init(struct mm_struct *mm) {}
+#endif
+
 #endif /* _LINUX_SCHED_MM_H */
diff --git a/kernel/fork.c b/kernel/fork.c
@@ -97,6 +97,7 @@
 #include <linux/scs.h>
 #include <linux/io_uring.h>
 #include <linux/bpf.h>
+#include <linux/sched/mm.h>
 
 #include <asm/pgalloc.h>
 #include <linux/uaccess.h>
@@ -1019,13 +1020,6 @@ 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_SVA
-	mm->pasid = INIT_PASID;
-#endif
-}
-
 static void mm_init_uprobes_state(struct mm_struct *mm)
 {
 #ifdef CONFIG_UPROBES
@@ -1054,7 +1048,7 @@ 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);
+	mm_pasid_init(mm);
 	RCU_INIT_POINTER(mm->exe_file, NULL);
 	mmu_notifier_subscriptions_init(mm);
 	init_tlb_flush_pending(mm);

diff --git a/mm/init-mm.c b/mm/init-mm.c
@@ -10,6 +10,7 @@
 
 #include <linux/atomic.h>
 #include <linux/user_namespace.h>
+#include <linux/ioasid.h>
 #include <asm/mmu.h>
 
 #ifndef INIT_MM_CONTEXT
@@ -38,6 +39,9 @@ struct mm_struct init_mm = {
 	.mmlist		= LIST_HEAD_INIT(init_mm.mmlist),
 	.user_ns	= &init_user_ns,
 	.cpu_bitmap	= CPU_BITS_NONE,
+#ifdef CONFIG_IOMMU_SVA
+	.pasid		= INVALID_IOASID,
+#endif
 	INIT_MM_CONTEXT(init_mm)
 };