[PATCH] target/s390x: Fix emulation of the VISTR instruction

[Thomas Huth <thuth@redhat.com>]

The element size is encoded in the M3 field, not in the M4
field. Let's also add a TCG test that shows the failing
behavior without this fix.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1248
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 tests/tcg/s390x/vf.c                | 50 +++++++++++++++++++++++++++++
 target/s390x/tcg/translate_vx.c.inc |  2 +-
 tests/tcg/s390x/Makefile.target     |  6 ++++
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 tests/tcg/s390x/vf.c

diff --git a/tests/tcg/s390x/vf.c b/tests/tcg/s390x/vf.c
new file mode 100644
index 0000000000..fdc424ce7c
--- /dev/null
+++ b/tests/tcg/s390x/vf.c
@@ -0,0 +1,50 @@
+/*
+ * vf: vector facility tests
+ */
+#include <stdint.h>
+#include <stdio.h>
+#include "vx.h"
+
+static inline void vistr(S390Vector *v1, S390Vector *v2,
+                         const uint8_t m3, const uint8_t m5)
+{
+    asm volatile("vistr %[v1], %[v2], %[m3], %[m5]\n"
+                : [v1] "=v" (v1->v)
+                : [v2]  "v" (v2->v)
+                , [m3]  "i" (m3)
+                , [m5]  "i" (m5)
+                : "cc");
+}
+
+static int test_vistr(void)
+{
+    S390Vector vd = {};
+    S390Vector vs16 = {
+        .h[0] = 0x1234, .h[1] = 0x0056, .h[2] = 0x7800, .h[3] = 0x0000,
+        .h[4] = 0x0078, .h[5] = 0x0000, .h[6] = 0x6543, .h[7] = 0x2100
+    };
+    S390Vector vs32 = {
+        .w[0] = 0x12340000, .w[1] = 0x78654300,
+        .w[2] = 0x0, .w[3] = 0x12,
+    };
+
+    vistr(&vd, &vs16, 1, 0);
+    if (vd.h[0] != 0x1234 || vd.h[1] != 0x0056 || vd.h[2] != 0x7800 ||
+        vd.h[3] || vd.h[4] || vd.h[5] || vd.h[6] || vd.h[7]) {
+        puts("ERROR: vitrh failed!");
+        return 1;
+    }
+
+    vistr(&vd, &vs32, 2, 0);
+    if (vd.w[0] != 0x12340000 || vd.w[1] != 0x78654300 || vd.w[2] || vd.w[3]) {
+        puts("ERROR: vitrf failed!");
+        return 1;
+    }
+
+    return 0;
+}
+
+int main(int argc, char *argv[])
+{
+    return test_vistr();
+}
diff --git a/target/s390x/tcg/translate_vx.c.inc b/target/s390x/tcg/translate_vx.c.inc
index 3526ba3e3b..b69c1a111c 100644
--- a/target/s390x/tcg/translate_vx.c.inc
+++ b/target/s390x/tcg/translate_vx.c.inc
@@ -2723,7 +2723,7 @@ static DisasJumpType op_vfene(DisasContext *s, DisasOps *o)
 
 static DisasJumpType op_vistr(DisasContext *s, DisasOps *o)
 {
-    const uint8_t es = get_field(s, m4);
+    const uint8_t es = get_field(s, m3);
     const uint8_t m5 = get_field(s, m5);
     static gen_helper_gvec_2 * const g[3] = {
         gen_helper_gvec_vistr8,
diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
index c830313e67..f8e71a9439 100644
--- a/tests/tcg/s390x/Makefile.target
+++ b/tests/tcg/s390x/Makefile.target
@@ -18,6 +18,12 @@ TESTS+=signals-s390x
 TESTS+=branch-relative-long
 TESTS+=noexec
 
+Z13_TESTS=vf
+vf: LDFLAGS+=-lm
+$(Z13_TESTS): CFLAGS+=-march=z13 -O2
+TESTS+=$(if $(shell $(CC) -march=z13 -S -o /dev/null -xc /dev/null \
+			 >/dev/null 2>&1 && echo OK),$(Z13_TESTS))
+
 Z14_TESTS=vfminmax
 vfminmax: LDFLAGS+=-lm
 $(Z14_TESTS): CFLAGS+=-march=z14 -O2
-- 
2.31.1