s390x: Implement SAM{24,31,64}

The SAM instructions simply change 2 bits in PSW.MASK to advertise
the current memory mode. While we can't fully guarantee that 31 bit
mode (or even remotely 24 bit mode) actually work correctly, we don't
check whether lpswe modifies these bits, so we shouldn't keep the
guest from executing SAM instructions either.

This patch implements all SAM instrutions with their actual PSW changing
semantics, making more recent Linux kernels boot properly which do issue
a SAM31 call during early boot.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Richard Henderson <rth@twiddle.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/target-s390x/translate.c b/target-s390x/translate.c
index 0cb036f667..dbf1993d46 100644
--- a/target-s390x/translate.c
+++ b/target-s390x/translate.c
@@ -2925,6 +2925,18 @@ static ExitStatus op_sacf(DisasContext *s, DisasOps *o)
     /* Addressing mode has changed, so end the block.  */
     return EXIT_PC_STALE;
 }
+
+static ExitStatus op_sam(DisasContext *s, DisasOps *o)
+{
+    int sam = s->insn->data;
+    TCGv_i64 tsam = tcg_const_i64(sam);
+
+    /* Overwrite PSW_MASK_64 and PSW_MASK_32 */
+    tcg_gen_deposit_i64(psw_mask, psw_mask, tsam, 31, 2);
+
+    tcg_temp_free_i64(tsam);
+    return EXIT_PC_STALE;
+}
 #endif
 
 static ExitStatus op_sar(DisasContext *s, DisasOps *o)