[PATCH 4/6] target/ppc: Alignment faults do not set DSISR in ISA v3.0 onward

[Nicholas Piggin <npiggin@gmail.com>]

This optional behavior was removed from the ISA in v3.0, see
Summary of Changes preface:

  Data Storage Interrupt Status Register for Alignment Interrupt:
  Simplifies the Alignment interrupt by remov- ing the Data Storage
  Interrupt Status Register (DSISR) from the set of registers modified
  by the Alignment interrupt.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/excp_helper.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 5f0e363363..c8b8eca3b1 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -1456,13 +1456,22 @@ static void powerpc_excp_books(PowerPCCPU *cpu, int excp)
         break;
     }
     case POWERPC_EXCP_ALIGN:     /* Alignment exception                      */
-        /* Get rS/rD and rA from faulting opcode */
-        /*
-         * Note: the opcode fields will not be set properly for a
-         * direct store load/store, but nobody cares as nobody
-         * actually uses direct store segments.
-         */
-        env->spr[SPR_DSISR] |= (env->error_code & 0x03FF0000) >> 16;
+        switch (env->excp_model) {
+        case POWERPC_EXCP_970:
+        case POWERPC_EXCP_POWER7:
+        case POWERPC_EXCP_POWER8:
+            /* Get rS/rD and rA from faulting opcode */
+            /*
+             * Note: the opcode fields will not be set properly for a
+             * direct store load/store, but nobody cares as nobody
+             * actually uses direct store segments.
+             */
+            env->spr[SPR_DSISR] |= (env->error_code & 0x03FF0000) >> 16;
+            break;
+        default:
+            /* Optional DSISR update was removed from ISA v3.0 */
+            break;
+        }
         break;
     case POWERPC_EXCP_PROGRAM:   /* Program exception                        */
         switch (env->error_code & ~0xF) {
-- 
2.37.2