[kvm-unit-tests PATCH v6 10/10] s390x: css: ping pong

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

To test a write command with the SSCH instruction we need a QEMU device,
with control unit type 0xC0CA. The PONG device is such a device.

This type of device responds to PONG_WRITE requests by incrementing an
integer, stored as a string at offset 0 of the CCW data.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
 s390x/css.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/s390x/css.c b/s390x/css.c
index b9dbf01..7cd8731 100644
--- a/s390x/css.c
+++ b/s390x/css.c
@@ -23,6 +23,12 @@
 #define PSW_PRG_MASK (PSW_MASK_EA | PSW_MASK_BA)
 
 #define PONG_CU_TYPE		0xc0ca
+/* Channel Commands for PONG device */
+#define PONG_WRITE	0x21 /* Write */
+#define PONG_READ	0x22 /* Read buffer */
+
+#define BUFSZ	9
+static char buffer[BUFSZ];
 
 struct lowcore *lowcore = (void *)0x0;
 
@@ -262,6 +268,53 @@ unreg_cb:
 	unregister_io_int_func(irq_io);
 }
 
+static void test_ping(void)
+{
+	int success, result;
+	int cnt = 0, max = 4;
+
+	if (senseid.cu_type != PONG_CU) {
+		report_skip("No PONG, no ping-pong");
+		return;
+	}
+
+	result = register_io_int_func(irq_io);
+	if (result) {
+		report(0, "Could not register IRQ handler");
+		return;
+	}
+
+	while (cnt++ < max) {
+		snprintf(buffer, BUFSZ, "%08x\n", cnt);
+		success = start_subchannel(PONG_WRITE, buffer, BUFSZ);
+		if (!success) {
+			report(0, "start_subchannel failed");
+			goto unreg_cb;
+		}
+
+		wfi(PSW_MASK_IO);
+
+		success = start_subchannel(PONG_READ, buffer, BUFSZ);
+		if (!success) {
+			report(0, "start_subchannel failed");
+			goto unreg_cb;
+		}
+
+		wfi(PSW_MASK_IO);
+
+		result = atol(buffer);
+		if (result != (cnt + 1)) {
+			report(0, "Bad answer from pong: %08x - %08x",
+			       cnt, result);
+			goto unreg_cb;
+		}
+	}
+	report(1, "ping-pong count 0x%08x", cnt);
+
+unreg_cb:
+	unregister_io_int_func(irq_io);
+}
+
 static struct {
 	const char *name;
 	void (*func)(void);
@@ -269,6 +322,7 @@ static struct {
 	{ "enumerate (stsch)", test_enumerate },
 	{ "enable (msch)", test_enable },
 	{ "sense (ssch/tsch)", test_sense },
+	{ "ping-pong (ssch/tsch)", test_ping },
 	{ NULL, NULL }
 };
 
-- 
2.25.1