[kvm-unit-tests PATCH v4 6/8] s390x: Add more tests for STSCH

[Nico Boehr <nrb@linux.ibm.com>]

css_lib extensively uses STSCH, but two more cases deserve their own
tests:

- unaligned address for SCHIB. We check for misalignment by 1 and 2
  bytes.
- channel not operational
- bit 47 in SID not set
- bit 5 of PMCW flags.
  As per the principles of operation, bit 5 of the PMCW flags shall be
  ignored by msch and always stored as zero by stsch.

  Older QEMU versions require this bit to always be zero on msch,
  which is why this test may fail. A fix is available in QEMU master
  commit 2df59b73e086 ("s390x/css: fix PMCW invalid mask").

Here's the QEMU PMCW invalid mask fix: https://lists.nongnu.org/archive/html/qemu-s390x/2021-12/msg00100.html

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 s390x/css.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/s390x/css.c b/s390x/css.c
index 7fe5283c41d0..dd84e670ce99 100644
--- a/s390x/css.c
+++ b/s390x/css.c
@@ -501,6 +501,86 @@ static void test_ssch(void)
 	report_prefix_pop();
 }
 
+static void test_stsch(void)
+{
+	const int align_to = 4;
+	struct schib schib;
+	int cc;
+
+	if (!test_device_sid) {
+		report_skip("No device");
+		return;
+	}
+
+	report_prefix_push("Unaligned");
+	for (int i = 1; i < align_to; i *= 2) {
+		report_prefix_pushf("%d", i);
+
+		expect_pgm_int();
+		stsch(test_device_sid, (struct schib *)(alignment_test_page + i));
+		check_pgm_int_code(PGM_INT_CODE_SPECIFICATION);
+
+		report_prefix_pop();
+	}
+	report_prefix_pop();
+
+	report_prefix_push("Invalid subchannel number");
+	cc = stsch(0x0001ffff, &schib);
+	report(cc == 3, "Channel not operational");
+	report_prefix_pop();
+
+	/*
+	 * No matter if multiple-subchannel-set facility is installed, bit 47
+	 * always needs to be 1.
+	 */
+	report_prefix_push("Bit 47 in SID is zero");
+	expect_pgm_int();
+	stsch(0x0000ffff, &schib);
+	check_pgm_int_code(PGM_INT_CODE_OPERAND);
+	report_prefix_pop();
+}
+
+/*
+ * According to architecture MSCH does ignore bit 5 of the second word
+ * but STSCH will store bit 5 as zero.
+ */
+static void test_pmcw_bit5(void)
+{
+	int cc;
+	uint16_t old_pmcw_flags;
+
+	cc = stsch(test_device_sid, &schib);
+	if (cc) {
+		report_fail("stsch: sch %08x failed with cc=%d", test_device_sid, cc);
+		return;
+	}
+	old_pmcw_flags = schib.pmcw.flags;
+
+	report_prefix_push("Bit 5 set");
+
+	schib.pmcw.flags = old_pmcw_flags | BIT(15 - 5);
+	cc = msch(test_device_sid, &schib);
+	report(!cc, "MSCH cc == 0");
+
+	cc = stsch(test_device_sid, &schib);
+	report(!cc, "STSCH cc == 0");
+	report(!(schib.pmcw.flags & BIT(15 - 5)), "STSCH PMCW Bit 5 is clear");
+
+	report_prefix_pop();
+
+	report_prefix_push("Bit 5 clear");
+
+	schib.pmcw.flags = old_pmcw_flags & ~BIT(15 - 5);
+	cc = msch(test_device_sid, &schib);
+	report(!cc, "MSCH cc == 0");
+
+	cc = stsch(test_device_sid, &schib);
+	report(!cc, "STSCH cc == 0");
+	report(!(schib.pmcw.flags & BIT(15 - 5)), "STSCH PMCW Bit 5 is clear");
+
+	report_prefix_pop();
+}
+
 static struct {
 	const char *name;
 	void (*func)(void);
@@ -516,6 +596,8 @@ static struct {
 	{ "msch", test_msch },
 	{ "stcrw", test_stcrw },
 	{ "ssch", test_ssch },
+	{ "stsch", test_stsch },
+	{ "pmcw bit 5 ignored", test_pmcw_bit5 },
 	{ NULL, NULL }
 };
 
-- 
2.31.1