[qemu-s390x] [PATCH v2 21/28] s390x/tcg: XC: Fault-safe handling

[David Hildenbrand]

We can process a maximum of 256 bytes, crossing two pages. While at it,
increment the length once.

Signed-off-by: David Hildenbrand <address@hidden>
---
 target/s390x/mem_helper.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index ff57fec8de..88ff6c21ed 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -354,23 +354,31 @@ uint32_t HELPER(nc)(CPUS390XState *env, uint32_t l, 
uint64_t dest,
 static uint32_t do_helper_xc(CPUS390XState *env, uint32_t l, uint64_t dest,
                              uint64_t src, uintptr_t ra)
 {
+    S390Access srca1, srca2, desta;
     uint32_t i;
     uint8_t c = 0;
 
     HELPER_LOG("%s l %d dest %" PRIx64 " src %" PRIx64 "\n",
                __func__, l, dest, src);
 
+    /* XC always processes one more byte than specified - maximum is 256 */
+    l++;
+
     /* xor with itself is the same as memset(0) */
     if (src == dest) {
-        access_memset(env, dest, 0, l + 1, ra);
+        access_memset(env, dest, 0, l, ra);
         return 0;
     }
 
-    for (i = 0; i <= l; i++) {
-        uint8_t x = cpu_ldub_data_ra(env, src + i, ra);
-        x ^= cpu_ldub_data_ra(env, dest + i, ra);
+    srca1 = access_prepare(env, src, l, MMU_DATA_LOAD, ra);
+    srca2 = access_prepare(env, dest, l, MMU_DATA_LOAD, ra);
+    desta = access_prepare(env, dest, l, MMU_DATA_STORE, ra);
+    for (i = 0; i < l; i++) {
+        const uint8_t x = access_get_byte(env, &srca1, i, ra) ^
+                          access_get_byte(env, &srca2, i, ra);
+
         c |= x;
-        cpu_stb_data_ra(env, dest + i, x, ra);
+        access_set_byte(env, &desta, i, x, ra);
     }
     return c != 0;
 }
-- 
2.21.0