[PATCH v6 12/12] s390/mm: Add huge page gmap linking support

[Janosch Frank <frankja@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
---
 arch/s390/mm/gmap.c    |  9 ++++++---
 arch/s390/mm/pgtable.c | 12 ++++++------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 8b1a293b00d3..1399392d2fbd 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@xxxxxxxxxx>
+ *		 David Hildenbrand <david@xxxxxxxxxx>
+ *		 Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
  */
 
 #include <linux/kernel.h>
@@ -589,8 +591,8 @@ 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);
@@ -1631,6 +1633,7 @@ 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 161e08437681..1275f73b5c39 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -348,7 +348,7 @@ 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);
 }
 
@@ -358,15 +358,15 @@ 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);
 	}
 }
@@ -435,7 +435,7 @@ pmd_t pmdp_xchg_direct(struct mm_struct *mm, unsigned long addr,
 	pmd_t old;
 
 	preempt_disable();
-	if (mm_has_pgste(mm)) {
+	if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m) {
 		pmdp_clear_skeys(mm, pmdp, new);
 		pmdp_notify(mm, addr);
 	}
@@ -452,7 +452,7 @@ pmd_t pmdp_xchg_lazy(struct mm_struct *mm, unsigned long addr,
 	pmd_t old;
 
 	preempt_disable();
-	if (mm_has_pgste(mm)) {
+	if (mm_has_pgste(mm) && mm->context.allow_gmap_hpage_1m) {
 		pmdp_clear_skeys(mm, pmdp, new);
 		pmdp_notify(mm, addr);
 	}
-- 
2.14.3