s390/mm: Add huge page gmap linking support

Let's allow huge pmd linking when enabled through the
KVM_CAP_S390_HPAGE_1M capability. Also we can now restrict gmap
invalidation and notification to the cases where the capability has
been activated and save some cycles when that's not the case.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>

4 files changed, 13 insertions, 7 deletions

diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index f5ff9dbad8ac..f31a15044c24 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -24,6 +24,8 @@ typedef struct {
         unsigned int uses_skeys:1;
         /* The mmu context uses CMM. */
         unsigned int uses_cmm:1;
+        /* The gmaps associated with this context are allowed to use huge pages. */
+        unsigned int allow_gmap_hpage_1m:1;
 } mm_context_t;
 
 #define INIT_MM_CONTEXT(name)                                              \
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index d16bc79c30bb..0717ee76885d 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -32,6 +32,7 @@ static inline int init_new_context(struct task_struct *tsk,
         mm->context.has_pgste = 0;
         mm->context.uses_skeys = 0;
         mm->context.uses_cmm = 0;
+        mm->context.allow_gmap_hpage_1m = 0;
 #endif
         switch (mm->context.asce_limit) {
         case _REGION2_SIZE:
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 736ed32a83c5..bb44990c8212 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2,8 +2,10 @@
 /*
  *  KVM guest address space mapping code
  *
- *    Copyright IBM Corp. 2007, 2016
+ *    Copyright IBM Corp. 2007, 2016, 2018
  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ *               David Hildenbrand <david@redhat.com>
+ *               Janosch Frank <frankja@linux.vnet.ibm.com>
  */
 
 #include <linux/kernel.h>
@@ -588,8 +590,8 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
                 return -EFAULT;
         pmd = pmd_offset(pud, vmaddr);
         VM_BUG_ON(pmd_none(*pmd));
-        /* large pmds cannot yet be handled */
-        if (pmd_large(*pmd))
+        /* Are we allowed to use huge pages? */
+        if (pmd_large(*pmd) && !gmap->mm->context.allow_gmap_hpage_1m)
                 return -EFAULT;
         /* Link gmap segment table entry location to page table. */
         rc = radix_tree_preload(GFP_KERNEL);
@@ -1632,6 +1634,7 @@ struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
         unsigned long limit;
         int rc;
 
+        BUG_ON(parent->mm->context.allow_gmap_hpage_1m);
         BUG_ON(gmap_is_shadow(parent));
         spin_lock(&parent->shadow_lock);
         sg = gmap_find_shadow(parent, asce, edat_level);
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 37d68706f5aa..f2cc7da473e4 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -347,7 +347,7 @@ static inline void pmdp_idte_local(struct mm_struct *mm,
                             mm->context.asce, IDTE_LOCAL);
         else
                 __pmdp_idte(addr, pmdp, 0, 0, IDTE_LOCAL);
-        if (mm_has_pgste(mm))
+        if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
                 gmap_pmdp_idte_local(mm, addr);
 }
 
@@ -357,15 +357,15 @@ static inline void pmdp_idte_global(struct mm_struct *mm,
         if (MACHINE_HAS_TLB_GUEST) {
                 __pmdp_idte(addr, pmdp, IDTE_NODAT | IDTE_GUEST_ASCE,
                             mm->context.asce, IDTE_GLOBAL);
-                if (mm_has_pgste(mm))
+                if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
                         gmap_pmdp_idte_global(mm, addr);
         } else if (MACHINE_HAS_IDTE) {
                 __pmdp_idte(addr, pmdp, 0, 0, IDTE_GLOBAL);
-                if (mm_has_pgste(mm))
+                if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
                         gmap_pmdp_idte_global(mm, addr);
         } else {
                 __pmdp_csp(pmdp);
-                if (mm_has_pgste(mm))
+                if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m)
                         gmap_pmdp_csp(mm, addr);
         }
 }