[kvm-unit-tests v2 PATCH] s390x/cpumodel: The missing DFP facility on TCG is expected

[Thomas Huth <thuth@redhat.com>]

When running the kvm-unit-tests with TCG on s390x, the cpumodel test
always reports the error about the missing DFP (decimal floating point)
facility. This is kind of expected, since DFP is not required for
running Linux and thus nobody is really interested in implementing
this facility in TCG. Thus let's mark this as an expected error instead,
so that we can run the kvm-unit-tests also with TCG without getting
test failures that we do not care about.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 v2:
 - Rewrote the logic, introduced expected_tcg_fail flag
 - Use manufacturer string instead of VM name to detect TCG

 s390x/cpumodel.c | 49 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 43 insertions(+), 6 deletions(-)

diff --git a/s390x/cpumodel.c b/s390x/cpumodel.c
index 5d232c6..190ceb2 100644
--- a/s390x/cpumodel.c
+++ b/s390x/cpumodel.c
@@ -11,14 +11,19 @@
  */
 
 #include <asm/facility.h>
+#include <alloc_page.h>
 
-static int dep[][2] = {
+static struct {
+	int facility;
+	int implied;
+	bool expected_tcg_fail;
+} dep[] = {
 	/* from SA22-7832-11 4-98 facility indications */
 	{   4,   3 },
 	{   5,   3 },
 	{   5,   4 },
 	{  19,  18 },
-	{  37,  42 },
+	{  37,  42, true },  /* TCG does not have DFP and won't get it soon */
 	{  43,  42 },
 	{  73,  49 },
 	{ 134, 129 },
@@ -38,6 +43,36 @@ static int dep[][2] = {
 	{ 155,  77 },
 };
 
+/*
+ * A hack to detect TCG (instead of KVM): QEMU uses "TCGguest" as guest
+ * name by default when we are running with TCG (otherwise it's "KVMguest")
+ */
+static bool is_tcg(void)
+{
+	const char qemu_ebcdic[] = { 0xd8, 0xc5, 0xd4, 0xe4 };
+	bool ret = false;
+	uint8_t *buf;
+
+	buf = alloc_page();
+	if (!buf)
+		return false;
+
+	if (stsi(buf, 1, 1, 1)) {
+		goto out;
+	}
+
+	/*
+	 * If the manufacturer string is "QEMU" in EBCDIC, then we are on TCG
+	 * (otherwise the string is "IBM" in EBCDIC)
+	 */
+	if (!memcmp(&buf[32], qemu_ebcdic, sizeof(qemu_ebcdic)))
+		ret =  true;
+out:
+	free_page(buf);
+	return ret;
+}
+
+
 int main(void)
 {
 	int i;
@@ -46,11 +81,13 @@ int main(void)
 
 	report_prefix_push("dependency");
 	for (i = 0; i < ARRAY_SIZE(dep); i++) {
-		if (test_facility(dep[i][0])) {
-			report(test_facility(dep[i][1]), "%d implies %d",
-				dep[i][0], dep[i][1]);
+		if (test_facility(dep[i].facility)) {
+			report_xfail(dep[i].expected_tcg_fail && is_tcg(),
+				     test_facility(dep[i].implied),
+				     "%d implies %d",
+				     dep[i].facility, dep[i].implied);
 		} else {
-			report_skip("facility %d not present", dep[i][0]);
+			report_skip("facility %d not present", dep[i].facility);
 		}
 	}
 	report_prefix_pop();
-- 
2.18.1