[kvm-unit-tests PATCH v3 7/9] s390x: css: msch, enable test

[Pierre Morel <pmorel@linux.ibm.com>]

A second step when testing the channel subsystem is to prepare a channel
for use.
This includes:
- Get the current SubCHannel Information Block (SCHIB) using STSCH
- Update it in memory to set the ENABLE bit
- Tell the CSS that the SCHIB has been modified using MSCH
- Get the SCHIB from the CSS again to verify that the subchannel is
  enabled.

This tests the success of the MSCH instruction by enabling a channel.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 s390x/css.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/s390x/css.c b/s390x/css.c
index 3d4a986..4c0031c 100644
--- a/s390x/css.c
+++ b/s390x/css.c
@@ -58,11 +58,50 @@ static void test_enumerate(void)
 	report("Tested %d devices, %d found", 1, scn, found);
 }
 
+static void test_enable(void)
+{
+	struct pmcw *pmcw = &schib.pmcw;
+	int cc;
+
+	if (!test_device_sid) {
+		report_skip("No device");
+		return;
+	}
+	/* Read the SCIB for this subchannel */
+	cc = stsch(test_device_sid, &schib);
+	if (cc) {
+		report("stsch cc=%d", 0, cc);
+		return;
+	}
+	/* Update the SCHIB to enable the channel */
+	pmcw->flags |= PMCW_ENABLE;
+
+	/* Tell the CSS we want to modify the subchannel */
+	cc = msch(test_device_sid, &schib);
+	if (cc) {
+		report("msch cc=%d", 0, cc);
+		return;
+	}
+
+	/* Read the SCHIB again to verify the enablement */
+	cc = stsch(test_device_sid, &schib);
+	if (cc) {
+		report("stsch cc=%d", 0, cc);
+		return;
+	}
+	if (!(pmcw->flags & PMCW_ENABLE)) {
+		report("Enable failed. pmcw: %x", 0, pmcw->flags);
+		return;
+	}
+	report("Tested", 1);
+}
+
 static struct {
 	const char *name;
 	void (*func)(void);
 } tests[] = {
 	{ "enumerate (stsch)", test_enumerate },
+	{ "enable (msch)", test_enable },
 	{ NULL, NULL }
 };
 
-- 
2.17.0