s390/mm: take the mmap_sem in kvm_s390_shadow_fault()

Instead of doing it in the caller, let's just take the mmap_sem
in kvm_s390_shadow_fault(). By taking it as read, we allow parallel
faulting on shadow page tables, gmap shadow code is prepared for that.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 15 insertions, 17 deletions

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index c5f79c1205cf..5b5eee2d51cd 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1091,26 +1091,24 @@ int kvm_s390_shadow_fault(struct gmap *sg, unsigned long saddr, int write)
         int dat_protection;
         int rc;
 
+        down_read(&sg->mm->mmap_sem);
+
         rc = gmap_shadow_pgt_lookup(sg, saddr, &pgt, &dat_protection);
-        if (rc) {
+        if (rc)
                 rc = kvm_s390_shadow_tables(sg, saddr, &pgt, &dat_protection);
-                if (rc)
-                        return rc;
-        }
 
         vaddr.addr = saddr;
-        rc = gmap_read_table(sg->parent, pgt + vaddr.px * 8, &pte.val);
-        if (rc)
-                return rc;
-        if (pte.i)
-                return PGM_PAGE_TRANSLATION;
-        if (pte.z || pte.co)
-                return PGM_TRANSLATION_SPEC;
+        if (!rc)
+                rc = gmap_read_table(sg->parent, pgt + vaddr.px * 8, &pte.val);
+        if (!rc && pte.i)
+                rc = PGM_PAGE_TRANSLATION;
+        if (!rc && (pte.z || pte.co))
+                rc = PGM_TRANSLATION_SPEC;
         dat_protection |= pte.p;
-        if (write && dat_protection)
-                return PGM_PROTECTION;
-        rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
-        if (rc)
-                return rc;
-        return 0;
+        if (!rc && write && dat_protection)
+                rc = PGM_PROTECTION;
+        if (!rc)
+                rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
+        up_read(&sg->mm->mmap_sem);
+        return rc;
 }