ppc: restrict the use of the rfi instruction

Power ISA 2.x has deleted the rfi instruction and rfid shoud be used
instead on cpus following this instruction set or later.

This will raise an invalid exception when rfi is used on such
processors: Book3S 64-bit processors.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
[clg: the required fix in openbios, commit b747b6acc272 ('ppc: use
      rfid when running under a CPU from the 970 family.'), is now
      merged in qemu under commit 5cebd885 ('Update OpenBIOS
      images to b747b6a built from submodule.') ]
Signed-off-by: NCédric Le Goater <clg@kaod.org>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

target-ppc/translate.c

@@ -3585,10 +3585,13 @@ static void gen_rfi(DisasContext *ctx)
 #if defined(CONFIG_USER_ONLY)
     GEN_PRIV;
 #else
-    /* FIXME: This instruction doesn't exist anymore on 64-bit server
-     * processors compliant with arch 2.x, we should remove it there,
-     * but we need to fix OpenBIOS not to use it on 970 first
+    /* This instruction doesn't exist anymore on 64-bit server
+     * processors compliant with arch 2.x
      */
+    if (ctx->insns_flags & PPC_SEGMENT_64B) {
+        gen_inval_exception(ctx, POWERPC_EXCP_INVAL_INVAL);
+        return;
+    }
     /* Restore CPU state */
     CHK_SV;
     gen_update_cfar(ctx, ctx->nip - 4);