s390/mm,kvm: flush gmap address space with IDTE

The __tlb_flush_mm() helper uses a global flush if the mm struct
has a gmap structure attached to it. Replace the global flush with
two individual flushes by means of the IDTE instruction if only a
single gmap is attached the the mm.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 34 insertions, 23 deletions

diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index 6d39329c894b..bea785d7f853 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -12,6 +12,7 @@ typedef struct {
         struct list_head pgtable_list;
         spinlock_t gmap_lock;
         struct list_head gmap_list;
+        unsigned long gmap_asce;
         unsigned long asce;
         unsigned long asce_limit;
         unsigned long vdso_base;
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index c6a088c91aee..515fea5a3fc4 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -21,6 +21,7 @@ static inline int init_new_context(struct task_struct *tsk,
         INIT_LIST_HEAD(&mm->context.gmap_list);
         cpumask_clear(&mm->context.cpu_attach_mask);
         atomic_set(&mm->context.flush_count, 0);
+        mm->context.gmap_asce = 0;
         mm->context.flush_mm = 0;
 #ifdef CONFIG_PGSTE
         mm->context.alloc_pgste = page_table_allocate_pgste;
diff --git a/arch/s390/include/asm/tlbflush.h b/arch/s390/include/asm/tlbflush.h
index 490014c48b13..39846100682a 100644
--- a/arch/s390/include/asm/tlbflush.h
+++ b/arch/s390/include/asm/tlbflush.h
@@ -60,18 +60,25 @@ static inline void __tlb_flush_full(struct mm_struct *mm)
         preempt_enable();
 }
 
-/*
- * Flush TLB entries for a specific ASCE on all CPUs. Should never be used
- * when more than one asce (e.g. gmap) ran on this mm.
- */
-static inline void __tlb_flush_asce(struct mm_struct *mm, unsigned long asce)
+static inline void __tlb_flush_mm(struct mm_struct *mm)
 {
+        unsigned long gmap_asce;
+
+        /*
+         * If the machine has IDTE we prefer to do a per mm flush
+         * on all cpus instead of doing a local flush if the mm
+         * only ran on the local cpu.
+         */
         preempt_disable();
         atomic_inc(&mm->context.flush_count);
-        if (MACHINE_HAS_IDTE)
-                __tlb_flush_idte(asce);
-        else
-                __tlb_flush_global();
+        gmap_asce = READ_ONCE(mm->context.gmap_asce);
+        if (MACHINE_HAS_IDTE && gmap_asce != -1UL) {
+                if (gmap_asce)
+                        __tlb_flush_idte(gmap_asce);
+                __tlb_flush_idte(mm->context.asce);
+        } else {
+                __tlb_flush_full(mm);
+        }
         /* Reset TLB flush mask */
         cpumask_copy(mm_cpumask(mm), &mm->context.cpu_attach_mask);
         atomic_dec(&mm->context.flush_count);
@@ -92,7 +99,7 @@ static inline void __tlb_flush_kernel(void)
 /*
  * Flush TLB entries for a specific ASCE on all CPUs.
  */
-static inline void __tlb_flush_asce(struct mm_struct *mm, unsigned long asce)
+static inline void __tlb_flush_mm(struct mm_struct *mm)
 {
         __tlb_flush_local();
 }
@@ -103,19 +110,6 @@ static inline void __tlb_flush_kernel(void)
 }
 #endif
 
-static inline void __tlb_flush_mm(struct mm_struct * mm)
-{
-        /*
-         * If the machine has IDTE we prefer to do a per mm flush
-         * on all cpus instead of doing a local flush if the mm
-         * only ran on the local cpu.
-         */
-        if (MACHINE_HAS_IDTE && list_empty(&mm->context.gmap_list))
-                __tlb_flush_asce(mm, mm->context.asce);
-        else
-                __tlb_flush_full(mm);
-}
-
 static inline void __tlb_flush_mm_lazy(struct mm_struct * mm)
 {
         if (mm->context.flush_mm) {
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 2ce6bb3bab32..3ba622702ce4 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -94,6 +94,7 @@ out:
 struct gmap *gmap_create(struct mm_struct *mm, unsigned long limit)
 {
         struct gmap *gmap;
+        unsigned long gmap_asce;
 
         gmap = gmap_alloc(limit);
         if (!gmap)
@@ -101,6 +102,11 @@ struct gmap *gmap_create(struct mm_struct *mm, unsigned long limit)
         gmap->mm = mm;
         spin_lock(&mm->context.gmap_lock);
         list_add_rcu(&gmap->list, &mm->context.gmap_list);
+        if (list_is_singular(&mm->context.gmap_list))
+                gmap_asce = gmap->asce;
+        else
+                gmap_asce = -1UL;
+        WRITE_ONCE(mm->context.gmap_asce, gmap_asce);
         spin_unlock(&mm->context.gmap_lock);
         return gmap;
 }
@@ -230,6 +236,7 @@ EXPORT_SYMBOL_GPL(gmap_put);
 void gmap_remove(struct gmap *gmap)
 {
         struct gmap *sg, *next;
+        unsigned long gmap_asce;
 
         /* Remove all shadow gmaps linked to this gmap */
         if (!list_empty(&gmap->children)) {
@@ -243,6 +250,14 @@ void gmap_remove(struct gmap *gmap)
         /* Remove gmap from the pre-mm list */
         spin_lock(&gmap->mm->context.gmap_lock);
         list_del_rcu(&gmap->list);
+        if (list_empty(&gmap->mm->context.gmap_list))
+                gmap_asce = 0;
+        else if (list_is_singular(&gmap->mm->context.gmap_list))
+                gmap_asce = list_first_entry(&gmap->mm->context.gmap_list,
+                                             struct gmap, list)->asce;
+        else
+                gmap_asce = -1UL;
+        WRITE_ONCE(gmap->mm->context.gmap_asce, gmap_asce);
         spin_unlock(&gmap->mm->context.gmap_lock);
         synchronize_rcu();
         /* Put reference */