[kvm-unit-tests PATCH] s390x: sie: Test whether the epoch extension field is working as expected

[Thomas Huth <thuth@redhat.com>]

We recently discovered a bug with the time management in nested scenarios
which got fixed by kernel commit "KVM: s390: vsie: Fix the initialization
of the epoch extension (epdx) field". This adds a simple test for this
bug so that it is easier to decide whether the host kernel of a machine
has already been fixed or not.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 s390x/sie.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/s390x/sie.c b/s390x/sie.c
index 87575b29..7ec4b030 100644
--- a/s390x/sie.c
+++ b/s390x/sie.c
@@ -58,6 +58,33 @@ static void test_diags(void)
 	}
 }
 
+static void test_epoch_ext(void)
+{
+	u32 instr[] = {
+		0xb2780000,	/* STCKE 0 */
+		0x83020044	/* DIAG 0x44 to intercept */
+	};
+
+	if (!test_facility(139)) {
+		report_skip("epdx: Multiple Epoch Facility is not available");
+		return;
+	}
+
+	guest[0] = 0x00;
+	memcpy(guest_instr, instr, sizeof(instr));
+
+	vm.sblk->gpsw.addr = PAGE_SIZE * 2;
+	vm.sblk->gpsw.mask = PSW_MASK_64;
+
+	vm.sblk->ecd |= ECD_MEF;
+	vm.sblk->epdx = 0x47;	/* Setting the epoch extension here ... */
+
+	sie(&vm);
+
+	/* ... should result in the same epoch extension here: */
+	report(guest[0] == 0x47, "epdx: different epoch is visible in the guest");
+}
+
 static void setup_guest(void)
 {
 	setup_vm();
@@ -80,6 +107,7 @@ int main(void)
 
 	setup_guest();
 	test_diags();
+	test_epoch_ext();
 	sie_guest_destroy(&vm);
 
 done:
-- 
2.31.1