[S390] kvm: fix address mode switching

598841ca9919d008b520114d8a4378c4ce4e40a1 ([S390] use gmap address
spaces for kvm guest images) changed kvm to use a separate address
space for kvm guests. This address space was switched in __vcpu_run
In some cases (preemption, page fault) there is the possibility that
this address space switch is lost.
The typical symptom was a huge amount of validity intercepts or
random guest addressing exceptions.
Fix this by doing the switch in sie_loop and sie_exit and saving the
address space in the gmap structure itself. Also use the preempt
notifier.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 2 insertions, 8 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 4d1f2bce87b3..f69ff3c13496 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -160,6 +160,8 @@ struct gmap *gmap_alloc(struct mm_struct *mm)
         table = (unsigned long *) page_to_phys(page);
         crst_table_init(table, _REGION1_ENTRY_EMPTY);
         gmap->table = table;
+        gmap->asce = _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH |
+                     _ASCE_USER_BITS | __pa(table);
         list_add(&gmap->list, &mm->context.gmap_list);
         return gmap;
 
@@ -240,10 +242,6 @@ EXPORT_SYMBOL_GPL(gmap_free);
  */
 void gmap_enable(struct gmap *gmap)
 {
-        /* Load primary space page table origin. */
-        S390_lowcore.user_asce = _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH |
-                                 _ASCE_USER_BITS | __pa(gmap->table);
-        asm volatile("lctlg 1,1,%0\n" : : "m" (S390_lowcore.user_asce) );
         S390_lowcore.gmap = (unsigned long) gmap;
 }
 EXPORT_SYMBOL_GPL(gmap_enable);
@@ -254,10 +252,6 @@ EXPORT_SYMBOL_GPL(gmap_enable);
  */
 void gmap_disable(struct gmap *gmap)
 {
-        /* Load primary space page table origin. */
-        S390_lowcore.user_asce =
-                gmap->mm->context.asce_bits | __pa(gmap->mm->pgd);
-        asm volatile("lctlg 1,1,%0\n" : : "m" (S390_lowcore.user_asce) );
         S390_lowcore.gmap = 0UL;
 }
 EXPORT_SYMBOL_GPL(gmap_disable);