KVM: s390: Add storage key facility interpretation control

Up to now we always expected to have the storage key facility
available for our (non-VSIE) KVM guests. For huge page support, we
need to be able to disable it, so let's introduce that now.

We add the use_skf variable to manage KVM storage key facility
usage. Also we rename use_skey in the mm context struct to uses_skeys
to make it more clear that it is an indication that the vm actively
uses storage keys.

Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 324f6f4..d16bc79 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -30,7 +30,7 @@ static inline int init_new_context(struct task_struct *tsk,
 		test_thread_flag(TIF_PGSTE) ||
 		(current->mm && current->mm->context.alloc_pgste);
 	mm->context.has_pgste = 0;
-	mm->context.use_skey = 0;
+	mm->context.uses_skeys = 0;
 	mm->context.uses_cmm = 0;
 #endif
 	switch (mm->context.asce_limit) {