Re: [PATCH v1 08/12] s390x/mmu_helper: avoid setting the storage key if nothing changed

[Thomas Huth]

On 05/08/2021 17.28, David Hildenbrand wrote:

Avoid setting the key if nothing changed.

Signed-off-by: David Hildenbrand <da...@redhat.com>
---
  target/s390x/mmu_helper.c | 11 +++++++----
  1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c
index 36ab4e9c81..0c2c39a970 100644
--- a/target/s390x/mmu_helper.c
+++ b/target/s390x/mmu_helper.c
@@ -301,7 +301,7 @@ static void mmu_handle_skey(target_ulong addr, int rw, int 
*flags)
  {
      static S390SKeysClass *skeyclass;
      static S390SKeysState *ss;
-    uint8_t key;
+    uint8_t key, old_key;
      int rc;

/*

@@ -337,6 +337,7 @@ static void mmu_handle_skey(target_ulong addr, int rw, int 
*flags)
          trace_get_skeys_nonzero(rc);
          return;
      }
+    old_key = key;

switch (rw) {

      case MMU_DATA_LOAD:
@@ -360,9 +361,11 @@ static void mmu_handle_skey(target_ulong addr, int rw, int 
*flags)
      /* Any store/fetch sets the reference bit */
      key |= SK_R;

- rc = skeyclass->set_skeys(ss, addr / TARGET_PAGE_SIZE, 1, &key);

-    if (rc) {
-        trace_set_skeys_nonzero(rc);
+    if (key != old_key) {
+        rc = skeyclass->set_skeys(ss, addr / TARGET_PAGE_SIZE, 1, &key);
+        if (rc) {
+            trace_set_skeys_nonzero(rc);
+        }
      }
  }

Reviewed-by: Thomas Huth <th...@redhat.com>