[kvm-unit-tests PATCH v2 5/5] s390x: Add test for STFLE interpretive execution (format-2)

Christoph Schlameuss
2026-03-24T15:28:58Z

From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

The STFLE instruction indicates installed facilities.
SIE has facilities for the interpretive execution of STFLE.
There are multiple possible formats for the control block.
Use a snippet guest executing STFLE to get the result of
interpretive execution and check the result.
With the addition of the format-2 control block invalid format
specifiers are now possible.
Test for the occurrence of optional validity intercepts.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Co-developed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
lib/s390x/sie.c | 11 +++++++
lib/s390x/sie.h | 1 +
s390x/stfle-sie.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++-------
3 files changed, 92 insertions(+), 11 deletions(-)

diff --git a/lib/s390x/sie.c b/lib/s390x/sie.c
index 0fa915cf028a1b35a76aa316dfd97308094a4682..17f0ef7eff427002dd6d74d98f58ed493457a7ce 100644
--- a/lib/s390x/sie.c
+++ b/lib/s390x/sie.c
@@ -42,6 +42,17 @@ void sie_check_validity(struct vm *vm, uint16_t vir_exp)
report(vir_exp == vir, "VALIDITY: %x", vir);
}

+void sie_check_optional_validity(struct vm *vm, uint16_t vir_exp)
+{
+ uint16_t vir = sie_get_validity(vm);
+
+ if (vir == 0xffff)
+ report_pass("optional VALIDITY: no");
+ else
+ report(vir_exp == vir, "optional VALIDITY: %x", vir);
+ vm->validity_expected = false;
+}
+
void sie_handle_validity(struct vm *vm)
{
if (vm->sblk->icptcode != ICPT_VALIDITY)
diff --git a/lib/s390x/sie.h b/lib/s390x/sie.h
index 3ec49ed0da6459a70689ce5a1a8a027a4113f2a4..8bea0b10b0a6894096ee83933a8bda11711a1949 100644
--- a/lib/s390x/sie.h
+++ b/lib/s390x/sie.h
@@ -51,6 +51,7 @@ void sie(struct vm *vm);
void sie_expect_validity(struct vm *vm);
uint16_t sie_get_validity(struct vm *vm);
void sie_check_validity(struct vm *vm, uint16_t vir_exp);
+void sie_check_optional_validity(struct vm *vm, uint16_t vir_exp);
void sie_handle_validity(struct vm *vm);

static inline bool sie_is_pv(struct vm *vm)
diff --git a/s390x/stfle-sie.c b/s390x/stfle-sie.c
index 21cf8ff8b6f6e9d61ee304c5748c36f718da65ab..5b642d9e8c3d775e078c1f09b87ad6822cd28a32 100644
--- a/s390x/stfle-sie.c
+++ b/s390x/stfle-sie.c
@@ -42,6 +42,7 @@ static struct guest_stfle_res run_guest(void)
uint64_t guest_stfle_addr;
uint64_t reg;

+ reset_guest(&vm);
sie(&vm);
assert(snippet_is_force_exit_value(&vm));
guest_stfle_addr = snippet_get_force_exit_value(&vm);
@@ -55,18 +56,73 @@ static struct guest_stfle_res run_guest(void)
static void test_stfle_format_0(void)
{
struct guest_stfle_res res;
+ int format_mask;

report_prefix_push("format-0");
- for (int j = 0; j < stfle_size(); j++)
- WRITE_ONCE((*fac)[j], prng64(&prng_s));
- vm.sblk->fac = (uint32_t)(uint64_t)fac;
- res = run_guest();
- report(res.len == stfle_size(), "stfle len correct");
- report(!memcmp(*fac, res.mem, res.len * sizeof(uint64_t)),
- "Guest facility list as specified");
+ /*
+ * There are multiple valid two bit format control values depending on
+ * the available facilities.
+ * The facility introduced last defines the validity of control bits.
+ */
+ format_mask = sclp_facilities.has_astfleie2 ? 3 : sclp_facilities.has_astfleie1;
+ for (int i = 0; i < 4; i++) {
+ if (i & format_mask)
+ continue;
+ report_prefix_pushf("format control %d", i);
+ for (int j = 0; j < stfle_size(); j++)
+ WRITE_ONCE((*fac)[j], prng64(&prng_s));
+ vm.sblk->fac = (uint32_t)(uint64_t)fac | i;
+ res = run_guest();
+ report(res.len == stfle_size(), "stfle len correct");
+ report(!memcmp(*fac, res.mem, res.len * sizeof(uint64_t)),
+ "Guest facility list as specified");
+ report_prefix_pop();
+ }
report_prefix_pop();
}

+static void test_stfle_format_2(void)
+{
+ const int max_stfle_len = 8;
+ int guest_max_stfle_len = 0;
+ struct guest_stfle_res res;
+ bool saturated = false;
+
+ report_prefix_push("format-2");
+ for (int i = 1; i <= max_stfle_len; i++) {
+ report_prefix_pushf("max STFLE len %d", i);
+
+ WRITE_ONCE((*fac)[0], i - 1);
+ for (int j = 0; j < i; j++)
+ WRITE_ONCE((*fac)[j + 1], prng64(&prng_s));
+ vm.sblk->fac = (uint32_t)(uint64_t)fac | 2;
+ res = run_guest();
+ /* len increases up to maximum (machine specific) */
+ if (res.len < i)
+ saturated = true;
+ if (saturated) {
+ report(res.len == guest_max_stfle_len, "stfle len correct");
+ } else {
+ report(res.len == i, "stfle len correct");
+ guest_max_stfle_len = i;
+ }
+ report(!memcmp(&(*fac)[1], res.mem, guest_max_stfle_len * sizeof(uint64_t)),
+ "Guest facility list as specified");
+
+ report_prefix_pop();
+ }
+ report_prefix_pop();
+}
+
+static void test_no_stfle_format(int format)
+{
+ reset_guest(&vm);
+ vm.sblk->fac = (uint32_t)(uint64_t)fac | format;
+ sie_expect_validity(&vm);
+ sie(&vm);
+ sie_check_optional_validity(&vm, 0x1330);
+}
+
struct args {
uint64_t seed;
};
@@ -119,20 +175,33 @@ static struct args parse_args(int argc, char **argv)
int main(int argc, char **argv)
{
struct args args = parse_args(argc, argv);
- bool run_format_0 = test_facility(7);

if (!sclp_facilities.has_sief2) {
report_skip("SIEF2 facility unavailable");
goto out;
}
- if (!run_format_0)
+ if (!test_facility(7)) {
report_skip("STFLE facility not available");
+ goto out;
+ }

report_info("PRNG seed: 0x%lx", args.seed);
prng_s = prng_init(args.seed);
setup_guest();
- if (run_format_0)
- test_stfle_format_0();
+ test_stfle_format_0();
+
+ if (!sclp_facilities.has_astfleie1)
+ test_no_stfle_format(1);
+
+ if (!sclp_facilities.has_astfleie2) {
+ test_no_stfle_format(2);
+ report_skip("alternate STFLE interpretive-execution facility 2 not available");
+ } else {
+ test_stfle_format_2();
+ }
+
+ test_no_stfle_format(3);
+
out:
return report_summary();
}

--
2.53.0