[RFC/PATCH v3 03/16] s390/mm: Introduce gmap_pmdp_xchg

[Janosch Frank <frankja@linux.vnet.ibm.com>]

When changing guest pmds, we don't need to take care of the
corresponding host pmd. This means, we don't need to flush the host
TLB entries and we don't need to notify on all gmaps.

Let's introduce a function, that exchanges a pmd and takes care of the
necessary flushing and notification.

Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
---
 arch/s390/mm/gmap.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 4471cb9..16c877a9 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -23,6 +23,9 @@
 
 #define GMAP_SHADOW_FAKE_TABLE 1ULL
 
+static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *old, pmd_t new,
+			   unsigned long gaddr);
+
 /**
  * gmap_alloc - allocate and initialize a guest address space
  * @mm: pointer to the parent mm_struct
@@ -2174,6 +2177,31 @@ void ptep_notify(struct mm_struct *mm, unsigned long vmaddr,
 }
 EXPORT_SYMBOL_GPL(ptep_notify);
 
+/**
+ * gmap_pmdp_xchg - exchange a gmap pmd with another and notify
+ * @gmap: pointer to the guest address space structure
+ * @pmdp: pointer to the pmd entry
+ * @new: replacement entry
+ * @gaddr: the affected guest address
+ *
+ * This function is assumed to be called with the guest_table_lock
+ * held.
+ */
+static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *pmdp, pmd_t new,
+			   unsigned long gaddr)
+{
+	if (MACHINE_HAS_TLB_GUEST)
+		__pmdp_idte(gaddr, (pmd_t *)pmdp,
+			    IDTE_GUEST_ASCE, gmap->asce,
+			    IDTE_GLOBAL);
+	if (MACHINE_HAS_IDTE)
+		__pmdp_idte(gaddr, (pmd_t *)pmdp,
+			    0, 0, IDTE_GLOBAL);
+	else
+		__pmdp_csp(pmdp);
+	*pmdp = new;
+}
+
 static inline void thp_split_mm(struct mm_struct *mm)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-- 
2.7.4