tests/tcg/s390x: Test unaligned accesses to lowcore

Add a small test to avoid regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220725223746.227063-3-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

tests/tcg/s390x/Makefile.softmmu-target

+S390X_SRC=$(SRC_PATH)/tests/tcg/s390x
+VPATH+=$(S390X_SRC)
+QEMU_OPTS=-action panic=exit-failure -kernel
+
+%: %.S
+	$(CC) -march=z13 -m64 -nostartfiles -static -Wl,-Ttext=0 \
+		-Wl,--build-id=none $< -o $@
+
+TESTS += unaligned-lowcore

tests/tcg/s390x/unaligned-lowcore.S

+    .org 0x1D0                         /* program new PSW */
+    .quad 0x2000000000000,0            /* disabled wait */
+    .org 0x200                         /* lowcore padding */
+
+    .globl _start
+_start:
+    lctlg %c0,%c0,_c0
+    vst %v0,_unaligned
+    lpswe quiesce_psw
+
+    .align 8
+quiesce_psw:
+    .quad 0x2000000000000,0xfff        /* see is_special_wait_psw() */
+_c0:
+    .quad 0x10060000                   /* lowcore protection, AFP, VX */
+
+    .byte 0
+_unaligned:
+    .octa 0