[kvm-unit-tests PATCH v2 0/5] s390x: Add test for STFLE interpretive execution (format-2)

[kvm-unit-tests PATCH v2 0/5] s390x: Add test for STFLE interpretive execution (format-2)

[Christoph Schlameuss]

Test the shadowing of format-2 facility list when running in VSIE.

The tests will skip the format 2 tests
* if running with unpatched kernels or qemu in G1 or G2
* if running on machines prior IBM z16 GA1 (where ASTFLEIE2 is not
  available)

Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: "Nico Böhr" <nrb@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Thomas Huth <thuth@redhat.com>
To: linux-s390@vger.kernel.org
Cc: kvm@vger.kernel.org

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
The original series was started by Nina and finished by me.

---
Changes in v2:
- Rework sclp_facilities_setup()
- Removed explicit manual padding from struct sclp_facilities
- Link to v1: https://lore.kernel.org/r/20260211-vsie-stfle-fac-v1-0-46c7aec5912b@linux.ibm.com

---
Christoph Schlameuss (2):
      s390x: sclp: Remove unnecessary padding from struct sclp_facilities
      s390x: sclp: Rework sclp_facilities_setup() for simpler control flow

Nina Schoetterl-Glausch (3):
      s390x: snippets: Add reset_guest() to lib
      s390x: sclp: Add detection of alternate STFLE facilities
      s390x: Add test for STFLE interpretive execution (format-2)

 lib/s390x/sclp.c    | 30 +++++++++++-------
 lib/s390x/sclp.h    |  5 ++-
 lib/s390x/sie.c     | 11 +++++++
 lib/s390x/sie.h     |  1 +
 lib/s390x/snippet.h |  6 ++++
 s390x/spec_ex-sie.c | 10 ++----
 s390x/stfle-sie.c   | 91 ++++++++++++++++++++++++++++++++++++++++++++++-------
 7 files changed, 123 insertions(+), 31 deletions(-)
---
base-commit: 86e53277ac80dabb04f4fa5fa6a6cc7649392bdc
change-id: 20260202-vsie-stfle-fac-403e4467d8e2

Best regards,
-- 
Christoph Schlameuss <schlameuss@linux.ibm.com>

[kvm-unit-tests PATCH v2 1/5] s390x: snippets: Add reset_guest() to lib

[Christoph Schlameuss]

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

Extract reset_guest from spec_ex-sie into the lib.
After reset_guest() the snippet can be executed again.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
 lib/s390x/snippet.h |  6 ++++++
 s390x/spec_ex-sie.c | 10 ++--------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/lib/s390x/snippet.h b/lib/s390x/snippet.h
index 910849aa186ce2f94c64ac1f40f8d6d7cdc36a1f..6f611de510d832f23384739606da13e71de3d6fd 100644
--- a/lib/s390x/snippet.h
+++ b/lib/s390x/snippet.h
@@ -83,6 +83,12 @@ static inline void snippet_init(struct vm *vm, const char *gbin,
 	vm->sblk->ictl = ICTL_OPEREXC | ICTL_PINT;
 }
 
+static inline void reset_guest(struct vm *vm)
+{
+	vm->sblk->gpsw = snippet_psw;
+	vm->sblk->icptcode = 0;
+}
+
 /*
  * Sets up a snippet UV/PV guest on top of an existing and initialized
  * SIE vm struct.
diff --git a/s390x/spec_ex-sie.c b/s390x/spec_ex-sie.c
index fe2f23ee3d84fa144416808cb4b353627fe87f3d..75625ecffc4a5a09ff7ef6136b7f1120a831a8c5 100644
--- a/s390x/spec_ex-sie.c
+++ b/s390x/spec_ex-sie.c
@@ -31,12 +31,6 @@ static void setup_guest(void)
 		     SNIPPET_LEN(c, spec_ex), SNIPPET_UNPACK_OFF);
 }
 
-static void reset_guest(void)
-{
-	vm.sblk->gpsw = snippet_psw;
-	vm.sblk->icptcode = 0;
-}
-
 static void test_spec_ex_sie(void)
 {
 	const char *msg;
@@ -45,7 +39,7 @@ static void test_spec_ex_sie(void)
 
 	report_prefix_push("SIE spec ex interpretation");
 	report_prefix_push("off");
-	reset_guest();
+	reset_guest(&vm);
 	sie(&vm);
 	/* interpretation off -> initial exception must cause interception */
 	report(vm.sblk->icptcode == ICPT_PROGI
@@ -56,7 +50,7 @@ static void test_spec_ex_sie(void)
 
 	report_prefix_push("on");
 	vm.sblk->ecb |= ECB_SPECI;
-	reset_guest();
+	reset_guest(&vm);
 	sie(&vm);
 	/* interpretation on -> configuration dependent if initial exception causes
 	 * interception, but invalid new program PSW must

-- 
2.53.0

[kvm-unit-tests PATCH v2 2/5] s390x: sclp: Remove unnecessary padding from struct sclp_facilities

[Christoph Schlameuss]

Struct sclp_facilities is only used within the guest to keep the facility
information. Nothing bad should happen when the struct size changes in the
future.

Suggested-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 lib/s390x/sclp.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
index 22f120d1b7ea7d1c3fe822385d0c689e5b3459fe..42a2f2e9f25a45d3ebd71729df0d9d6d93a4fb50 100644
--- a/lib/s390x/sclp.h
+++ b/lib/s390x/sclp.h
@@ -132,7 +132,6 @@ struct sclp_facilities {
 	uint64_t has_kss : 1;
 	uint64_t has_pfmfi : 1;
 	uint64_t has_ibs : 1;
-	uint64_t : 64 - 15;
 };
 
 /* bit number within a certain byte */

-- 
2.53.0

[kvm-unit-tests PATCH v2 3/5] s390x: sclp: Rework sclp_facilities_setup() for simpler control flow

[Christoph Schlameuss]

Reverse the order of operations to allow for early exits with increasing
cpu offsets when reading facility bits in the extended range.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 lib/s390x/sclp.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
index 2f902e39e785ff4e139a39be2ffe11b5fa01edc0..d624872cba608fcbbd0c482a25f091fe19475a43 100644
--- a/lib/s390x/sclp.c
+++ b/lib/s390x/sclp.c
@@ -154,17 +154,6 @@ void sclp_facilities_setup(void)
 	assert(read_info);
 
 	cpu = sclp_get_cpu_entries();
-	if (read_info->offset_cpu > 134)
-		sclp_facilities.has_diag318 = read_info->byte_134_diag318;
-	sclp_facilities.has_sop = sclp_feat_check(80, SCLP_FEAT_80_BIT_SOP);
-	sclp_facilities.has_gsls = sclp_feat_check(85, SCLP_FEAT_85_BIT_GSLS);
-	sclp_facilities.has_esop = sclp_feat_check(85, SCLP_FEAT_85_BIT_ESOP);
-	sclp_facilities.has_kss = sclp_feat_check(98, SCLP_FEAT_98_BIT_KSS);
-	sclp_facilities.has_cmma = sclp_feat_check(116, SCLP_FEAT_116_BIT_CMMA);
-	sclp_facilities.has_64bscao = sclp_feat_check(116, SCLP_FEAT_116_BIT_64BSCAO);
-	sclp_facilities.has_esca = sclp_feat_check(116, SCLP_FEAT_116_BIT_ESCA);
-	sclp_facilities.has_ibs = sclp_feat_check(117, SCLP_FEAT_117_BIT_IBS);
-	sclp_facilities.has_pfmfi = sclp_feat_check(117, SCLP_FEAT_117_BIT_PFMFI);
 
 	for (i = 0; i < read_info->entries_cpu; i++, cpu++) {
 		/*
@@ -184,6 +173,20 @@ void sclp_facilities_setup(void)
 			break;
 		}
 	}
+
+	sclp_facilities.has_sop = sclp_feat_check(80, SCLP_FEAT_80_BIT_SOP);
+	sclp_facilities.has_gsls = sclp_feat_check(85, SCLP_FEAT_85_BIT_GSLS);
+	sclp_facilities.has_esop = sclp_feat_check(85, SCLP_FEAT_85_BIT_ESOP);
+	sclp_facilities.has_kss = sclp_feat_check(98, SCLP_FEAT_98_BIT_KSS);
+	sclp_facilities.has_cmma = sclp_feat_check(116, SCLP_FEAT_116_BIT_CMMA);
+	sclp_facilities.has_64bscao = sclp_feat_check(116, SCLP_FEAT_116_BIT_64BSCAO);
+	sclp_facilities.has_esca = sclp_feat_check(116, SCLP_FEAT_116_BIT_ESCA);
+	sclp_facilities.has_ibs = sclp_feat_check(117, SCLP_FEAT_117_BIT_IBS);
+	sclp_facilities.has_pfmfi = sclp_feat_check(117, SCLP_FEAT_117_BIT_PFMFI);
+
+	if (read_info->offset_cpu <= 134)
+		return;
+	sclp_facilities.has_diag318 = read_info->byte_134_diag318;
 }
 
 /* Perform service call. Return 0 on success, non-zero otherwise. */

-- 
2.53.0

[kvm-unit-tests PATCH v2 4/5] s390x: sclp: Add detection of alternate STFLE facilities

[Christoph Schlameuss]

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

Detect availability of alternate STFLE interpretive execution facilities
1 and 2.

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/sclp.c | 5 +++++
 lib/s390x/sclp.h | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
index d624872cba608fcbbd0c482a25f091fe19475a43..77b2a5ec00d68ec7ee82da295f2f31c539b5c00c 100644
--- a/lib/s390x/sclp.c
+++ b/lib/s390x/sclp.c
@@ -181,12 +181,17 @@ void sclp_facilities_setup(void)
 	sclp_facilities.has_cmma = sclp_feat_check(116, SCLP_FEAT_116_BIT_CMMA);
 	sclp_facilities.has_64bscao = sclp_feat_check(116, SCLP_FEAT_116_BIT_64BSCAO);
 	sclp_facilities.has_esca = sclp_feat_check(116, SCLP_FEAT_116_BIT_ESCA);
+	sclp_facilities.has_astfleie1 = sclp_feat_check(116, SCLP_FEAT_116_BIT_ASTFLEIE1);
 	sclp_facilities.has_ibs = sclp_feat_check(117, SCLP_FEAT_117_BIT_IBS);
 	sclp_facilities.has_pfmfi = sclp_feat_check(117, SCLP_FEAT_117_BIT_PFMFI);
 
 	if (read_info->offset_cpu <= 134)
 		return;
 	sclp_facilities.has_diag318 = read_info->byte_134_diag318;
+
+	if (read_info->offset_cpu <= 139)
+		return;
+	sclp_facilities.has_astfleie2 = sclp_feat_check(139, SCLP_FEAT_139_BIT_ASTFLEIE2);
 }
 
 /* Perform service call. Return 0 on success, non-zero otherwise. */
diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
index 42a2f2e9f25a45d3ebd71729df0d9d6d93a4fb50..5345e1ff8057c787f3aaea0245fc1e19096c75e9 100644
--- a/lib/s390x/sclp.h
+++ b/lib/s390x/sclp.h
@@ -129,9 +129,11 @@ struct sclp_facilities {
 	uint64_t has_cmma : 1;
 	uint64_t has_64bscao : 1;
 	uint64_t has_esca : 1;
+	uint64_t has_astfleie1 : 1;
 	uint64_t has_kss : 1;
 	uint64_t has_pfmfi : 1;
 	uint64_t has_ibs : 1;
+	uint64_t has_astfleie2 : 1;
 };
 
 /* bit number within a certain byte */
@@ -142,8 +144,10 @@ struct sclp_facilities {
 #define SCLP_FEAT_116_BIT_64BSCAO	0
 #define SCLP_FEAT_116_BIT_CMMA		1
 #define SCLP_FEAT_116_BIT_ESCA		4
+#define SCLP_FEAT_116_BIT_ASTFLEIE1	7
 #define SCLP_FEAT_117_BIT_PFMFI		1
 #define SCLP_FEAT_117_BIT_IBS		2
+#define SCLP_FEAT_139_BIT_ASTFLEIE2	1
 
 typedef struct ReadInfo {
 	SCCBHeader h;

-- 
2.53.0

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

[Christoph Schlameuss]

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

Re: [kvm-unit-tests PATCH v2 2/5] s390x: sclp: Remove unnecessary padding from struct sclp_facilities

[Janosch Frank]

On 3/24/26 16:28, Christoph Schlameuss wrote:
> Struct sclp_facilities is only used within the guest to keep the facility
> information. Nothing bad should happen when the struct size changes in the
> future.
> 
> Suggested-by: Janosch Frank <frankja@linux.ibm.com>
> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

> ---
>   lib/s390x/sclp.h | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> index 22f120d1b7ea7d1c3fe822385d0c689e5b3459fe..42a2f2e9f25a45d3ebd71729df0d9d6d93a4fb50 100644
> --- a/lib/s390x/sclp.h
> +++ b/lib/s390x/sclp.h
> @@ -132,7 +132,6 @@ struct sclp_facilities {
>   	uint64_t has_kss : 1;
>   	uint64_t has_pfmfi : 1;
>   	uint64_t has_ibs : 1;
> -	uint64_t : 64 - 15;
>   };
>   
>   /* bit number within a certain byte */
> 

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

[Janosch Frank]

On 3/24/26 16:28, Christoph Schlameuss wrote:
> 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;

Without the KVM patches format_mask is 0.

> +	for (int i = 0; i < 4; i++) {

Why?
This test is only for format 0, no?

> +		if (i & format_mask)
> +			continue;

i & 0 is always false.

> +		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;

Since my mask is 0 and i can be 0 - 3 where values >0 can lead to 
validities (optional) this test can run into a validity at any point.

> +		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);
> +}

This needs a prefix, right now I see three of these skip reports and I 
don't know which format was tested:
PASS: optional VALIDITY: no

But looking at the code above I wonder if that should be folded into the 
test above if the logic is fixed.

> +
>   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();
> +	}
> +

Does this test work on LPAR and zVM?

> +	test_no_stfle_format(3);
> +
>   out:
>   	return report_summary();
>   }
> 

Re: [kvm-unit-tests PATCH v2 1/5] s390x: snippets: Add reset_guest() to lib

[Nico Boehr]

On Tue Mar 24, 2026 at 4:28 PM CET, Christoph Schlameuss wrote:
> From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
>
> Extract reset_guest from spec_ex-sie into the lib.
> After reset_guest() the snippet can be executed again.
>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

Reviewed-by: Nico Boehr <nrb@linux.ibm.com>

Re: [kvm-unit-tests PATCH v2 2/5] s390x: sclp: Remove unnecessary padding from struct sclp_facilities

[Nico Boehr]

On Tue Mar 24, 2026 at 4:28 PM CET, Christoph Schlameuss wrote:
> Struct sclp_facilities is only used within the guest to keep the facility
> information. Nothing bad should happen when the struct size changes in the
> future.
>
> Suggested-by: Janosch Frank <frankja@linux.ibm.com>
> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
> ---
>  lib/s390x/sclp.h | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> index 22f120d1b7ea7d1c3fe822385d0c689e5b3459fe..42a2f2e9f25a45d3ebd71729df0d9d6d93a4fb50 100644
> --- a/lib/s390x/sclp.h
> +++ b/lib/s390x/sclp.h
> @@ -132,7 +132,6 @@ struct sclp_facilities {
>  	uint64_t has_kss : 1;
>  	uint64_t has_pfmfi : 1;
>  	uint64_t has_ibs : 1;
> -	uint64_t : 64 - 15;
>  };

If I'm not mistaken this is already wrong if I did proper counting since
there are 17 bits and we only subtract 15.

Since bit fields are guaranteed to be allocated left to right (see [1], p 14),
this change makes sense.

Reviewed-by: Nico Boehr <nrb@linux.ibm.com>

[1] ELF Application Binary Interface s390x Supplement, Version 1.6

Re: [kvm-unit-tests PATCH v2 3/5] s390x: sclp: Rework sclp_facilities_setup() for simpler control flow

[Nico Boehr]

On Tue Mar 24, 2026 at 4:28 PM CET, Christoph Schlameuss wrote:
> Reverse the order of operations to allow for early exits with increasing
> cpu offsets when reading facility bits in the extended range.

Would be helpful to add a hint that this is needed for upcoming changes in this
series.

Otherwise LGTM.

Reviewed-by: Nico Boehr <nrb@linux.ibm.com>

Re: [kvm-unit-tests PATCH v2 4/5] s390x: sclp: Add detection of alternate STFLE facilities

[Nico Boehr]

On Tue Mar 24, 2026 at 4:28 PM CET, Christoph Schlameuss wrote:
[...]
> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
> index d624872cba608fcbbd0c482a25f091fe19475a43..77b2a5ec00d68ec7ee82da295f2f31c539b5c00c 100644
> --- a/lib/s390x/sclp.c
> +++ b/lib/s390x/sclp.c
[...]
>  	if (read_info->offset_cpu <= 134)
>  		return;
>  	sclp_facilities.has_diag318 = read_info->byte_134_diag318;
> +
> +	if (read_info->offset_cpu <= 139)
> +		return;
> +	sclp_facilities.has_astfleie2 = sclp_feat_check(139, SCLP_FEAT_139_BIT_ASTFLEIE2);

Help me understand which case is the odd one, the diag318 one where we access
read_info directly or this one where we use sclp_feat_check()?

Or is there a particular reason to do it this way that I didn't see?