[PATCH 0/4] KVM: s390: vsie: Implement ASTFLEIE facility 2

[PATCH 0/4] KVM: s390: vsie: Implement ASTFLEIE facility 2

[Christoph Schlameuss]

Add support for STFLE format 2 in VSIE guests.

The change requires qemu support to set the ASTFLEIE2 feature bit.
ASTFLEIE2 is available since IBM z16.
To function G1 has to run this KVM code and G1 and G2 have to run QEMU

Tests are implemented in kvm-unit-tests and sent as a series to that
list.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
The series was originally developed by Nina and only rebased and
slightly adjusted by me. It was not sent earlier since the accompanying
kvm-unit-tests and qemu changes were not ready.

---
Nina Schoetterl-Glausch (4):
      KVM: s390: Minor refactor of base/ext facility lists
      s390/sclp: Detect ASTFLEIE 2 facility
      KVM: s390: vsie: Refactor handle_stfle
      KVM: s390: vsie: Implement ASTFLEIE facility 2

 arch/s390/include/asm/sclp.h     |  1 +
 arch/s390/include/uapi/asm/kvm.h |  1 +
 arch/s390/kvm/kvm-s390.c         | 46 ++++++++++------------
 arch/s390/kvm/vsie.c             | 84 +++++++++++++++++++++++++++++++---------
 drivers/s390/char/sclp_early.c   |  4 +-
 5 files changed, 91 insertions(+), 45 deletions(-)
---
base-commit: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b
change-id: 20260129-vsie-alter-stfle-fac-b3d28b948146

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

[PATCH 1/4] KVM: s390: Minor refactor of base/ext facility lists

[Christoph Schlameuss]

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

Directly use the size of the arrays instead of going through the
indirection of kvm_s390_fac_size().
Don't use magic number for the number of entries in the non hypervisor
managed facility bit mask list.
Make the constraint of that number on kvm_s390_fac_base obvious.
Get rid of implicit double anding of stfle_fac_list.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 44 +++++++++++++++++++-------------------------
 1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 56a50524b3eee4e17b5b8a5833c2a560d120c443..797d77174fe692c1e63cacc38f251dd3bc98a23b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -231,33 +231,25 @@ static int async_destroy = 1;
 module_param(async_destroy, int, 0444);
 MODULE_PARM_DESC(async_destroy, "Asynchronous destroy for protected guests");
 
-/*
- * For now we handle at most 16 double words as this is what the s390 base
- * kernel handles and stores in the prefix page. If we ever need to go beyond
- * this, this requires changes to code, but the external uapi can stay.
- */
-#define SIZE_INTERNAL 16
-
+#define HMFAI_DWORDS 16
 /*
  * Base feature mask that defines default mask for facilities. Consists of the
  * defines in FACILITIES_KVM and the non-hypervisor managed bits.
  */
-static unsigned long kvm_s390_fac_base[SIZE_INTERNAL] = { FACILITIES_KVM };
+static unsigned long kvm_s390_fac_base[HMFAI_DWORDS] = { FACILITIES_KVM };
+static_assert(ARRAY_SIZE(((long[]){ FACILITIES_KVM })) <= HMFAI_DWORDS);
+static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= S390_ARCH_FAC_MASK_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= S390_ARCH_FAC_LIST_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= ARRAY_SIZE(stfle_fac_list));
+
 /*
  * Extended feature mask. Consists of the defines in FACILITIES_KVM_CPUMODEL
  * and defines the facilities that can be enabled via a cpu model.
  */
-static unsigned long kvm_s390_fac_ext[SIZE_INTERNAL] = { FACILITIES_KVM_CPUMODEL };
-
-static unsigned long kvm_s390_fac_size(void)
-{
-	BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_MASK_SIZE_U64);
-	BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_LIST_SIZE_U64);
-	BUILD_BUG_ON(SIZE_INTERNAL * sizeof(unsigned long) >
-		sizeof(stfle_fac_list));
-
-	return SIZE_INTERNAL;
-}
+static const unsigned long kvm_s390_fac_ext[] = { FACILITIES_KVM_CPUMODEL };
+static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= S390_ARCH_FAC_MASK_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= S390_ARCH_FAC_LIST_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= ARRAY_SIZE(stfle_fac_list));
 
 /* available cpu features supported by kvm */
 static DECLARE_BITMAP(kvm_s390_available_cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
@@ -3371,13 +3363,16 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm->arch.sie_page2->kvm = kvm;
 	kvm->arch.model.fac_list = kvm->arch.sie_page2->fac_list;
 
-	for (i = 0; i < kvm_s390_fac_size(); i++) {
+	for (i = 0; i < ARRAY_SIZE(kvm_s390_fac_base); i++) {
 		kvm->arch.model.fac_mask[i] = stfle_fac_list[i] &
-					      (kvm_s390_fac_base[i] |
-					       kvm_s390_fac_ext[i]);
+					      kvm_s390_fac_base[i];
 		kvm->arch.model.fac_list[i] = stfle_fac_list[i] &
 					      kvm_s390_fac_base[i];
 	}
+	for (i = 0; i < ARRAY_SIZE(kvm_s390_fac_ext); i++) {
+		kvm->arch.model.fac_mask[i] |= stfle_fac_list[i] &
+					       kvm_s390_fac_ext[i];
+	}
 	kvm->arch.model.subfuncs = kvm_s390_available_subfunc;
 
 	/* we are always in czam mode - even on pre z14 machines */
@@ -6040,9 +6035,8 @@ static int __init kvm_s390_init(void)
 		return -EINVAL;
 	}
 
-	for (i = 0; i < 16; i++)
-		kvm_s390_fac_base[i] |=
-			stfle_fac_list[i] & nonhyp_mask(i);
+	for (i = 0; i < HMFAI_DWORDS; i++)
+		kvm_s390_fac_base[i] |= nonhyp_mask(i);
 
 	r = __kvm_s390_init();
 	if (r)

-- 
2.53.0

[PATCH 2/4] s390/sclp: Detect ASTFLEIE 2 facility

[Christoph Schlameuss]

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

Detect alternate STFLE interpretive execution facility 2.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/include/asm/sclp.h   | 1 +
 drivers/s390/char/sclp_early.c | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/sclp.h b/arch/s390/include/asm/sclp.h
index 0f184dbdbe5e0748fcecbca38b9e55a56968dc79..0f21501d3e866338895caeed385aa4f586384d69 100644
--- a/arch/s390/include/asm/sclp.h
+++ b/arch/s390/include/asm/sclp.h
@@ -104,6 +104,7 @@ struct sclp_info {
 	unsigned char has_aisii : 1;
 	unsigned char has_aeni : 1;
 	unsigned char has_aisi : 1;
+	unsigned char has_astfleie2 : 1;
 	unsigned int ibc;
 	unsigned int mtid;
 	unsigned int mtid_cp;
diff --git a/drivers/s390/char/sclp_early.c b/drivers/s390/char/sclp_early.c
index 6bf501ad8ff0ea6d3df0a721f29fd24506409493..22dd797e62291fef087d46ac1c7f805486e3935b 100644
--- a/drivers/s390/char/sclp_early.c
+++ b/drivers/s390/char/sclp_early.c
@@ -61,8 +61,10 @@ static void __init sclp_early_facilities_detect(void)
 		sclp.has_sipl = !!(sccb->cbl & 0x4000);
 		sclp.has_sipl_eckd = !!(sccb->cbl & 0x2000);
 	}
-	if (sccb->cpuoff > 139)
+	if (sccb->cpuoff > 139) {
 		sclp.has_diag324 = !!(sccb->byte_139 & 0x80);
+		sclp.has_astfleie2 = !!(sccb->byte_139 & 0x40);
+	}
 	sclp.rnmax = sccb->rnmax ? sccb->rnmax : sccb->rnmax2;
 	sclp.rzm = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;
 	sclp.rzm <<= 20;

-- 
2.53.0

[PATCH 3/4] KVM: s390: vsie: Refactor handle_stfle

[Christoph Schlameuss]

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

Use switch case in anticipation of handling format-1 and format-2
facility list designations in the future.
As the alternate STFLE facilities are not enabled, only case 0 is
possible.
No functional change intended.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/include/uapi/asm/kvm.h |  1 +
 arch/s390/kvm/vsie.c             | 53 ++++++++++++++++++++++++++++------------
 2 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 60345dd2cba2d611b76f8b5c70eab8f0abab4b9b..4192769b5ce069ba28d00d7cf1c4f1b34037d633 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -444,6 +444,7 @@ struct kvm_s390_vm_cpu_machine {
 #define KVM_S390_VM_CPU_FEAT_PFMFI	11
 #define KVM_S390_VM_CPU_FEAT_SIGPIF	12
 #define KVM_S390_VM_CPU_FEAT_KSS	13
+#define KVM_S390_VM_CPU_FEAT_ASTFLEIE2	14
 struct kvm_s390_vm_cpu_feat {
 	__u64 feat[16];
 };
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index b526621d2a1b0a00cd63afd7a96b5c8da81984a7..3a90d4011bf06c35416ca2ea81eab1f0f71e8be4 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -6,12 +6,15 @@
  *
  *    Author(s): David Hildenbrand <dahi@linux.vnet.ibm.com>
  */
+#include <linux/align.h>
 #include <linux/vmalloc.h>
 #include <linux/kvm_host.h>
 #include <linux/bug.h>
+#include <linux/compiler.h>
 #include <linux/list.h>
 #include <linux/bitmap.h>
 #include <linux/sched/signal.h>
+#include <linux/stddef.h>
 #include <linux/io.h>
 #include <linux/mman.h>
 
@@ -1008,6 +1011,23 @@ static void retry_vsie_icpt(struct vsie_page *vsie_page)
 	clear_vsie_icpt(vsie_page);
 }
 
+static int handle_stfle_0(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
+			  u32 fac_list_origin)
+{
+	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+
+	/*
+	 * format-0 -> size of nested guest's facility list == guest's size
+	 * guest's size == host's size, since STFLE is interpretatively executed
+	 * using a format-0 for the guest, too.
+	 */
+	if (read_guest_real(vcpu, fac_list_origin, &vsie_page->fac,
+			    stfle_size() * sizeof(u64)))
+		return set_validity_icpt(scb_s, 0x1090U);
+	scb_s->fac = (u32)virt_to_phys(&vsie_page->fac);
+	return 0;
+}
+
 /*
  * Try to shadow + enable the guest 2 provided facility list.
  * Retry instruction execution if enabled for and provided by guest 2.
@@ -1017,29 +1037,30 @@ static void retry_vsie_icpt(struct vsie_page *vsie_page)
  */
 static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {
-	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
-	__u32 fac = READ_ONCE(vsie_page->scb_o->fac);
+	u32 fac = READ_ONCE(vsie_page->scb_o->fac);
+	int fac_list_format_mask, fac_list_format;
+	u32 fac_list_origin;
+	bool has_astfleie2;
 
-	/*
-	 * Alternate-STFLE-Interpretive-Execution facilities are not supported
-	 * -> format-0 flcb
-	 */
+	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct vsie_page, fac), 8));
 	if (fac && test_kvm_facility(vcpu->kvm, 7)) {
 		retry_vsie_icpt(vsie_page);
 		/*
 		 * The facility list origin (FLO) is in bits 1 - 28 of the FLD
 		 * so we need to mask here before reading.
 		 */
-		fac = fac & 0x7ffffff8U;
-		/*
-		 * format-0 -> size of nested guest's facility list == guest's size
-		 * guest's size == host's size, since STFLE is interpretatively executed
-		 * using a format-0 for the guest, too.
-		 */
-		if (read_guest_real(vcpu, fac, &vsie_page->fac,
-				    stfle_size() * sizeof(u64)))
-			return set_validity_icpt(scb_s, 0x1090U);
-		scb_s->fac = (u32)virt_to_phys(&vsie_page->fac);
+		fac_list_origin = fac & 0x7ffffff8U;
+		has_astfleie2 = test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_ASTFLEIE2);
+		fac_list_format_mask = has_astfleie2 ? 3 : 0;
+		fac_list_format = fac & fac_list_format_mask;
+		switch (fac_list_format) {
+		case 0:
+			return handle_stfle_0(vcpu, vsie_page, fac_list_origin);
+		case 1:
+		case 2:
+		case 3:
+			unreachable();
+		}
 	}
 	return 0;
 }

-- 
2.53.0

[PATCH 4/4] KVM: s390: vsie: Implement ASTFLEIE facility 2

[Christoph Schlameuss]

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

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

ASTFLEIE2 is available since IBM z16.
To function G1 has to run this KVM code and G1 and G2 have to run QEMU
with ASTFLEIE2 support.

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>
---
 arch/s390/kvm/kvm-s390.c |  2 ++
 arch/s390/kvm/vsie.c     | 33 +++++++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 797d77174fe692c1e63cacc38f251dd3bc98a23b..3f922b96356aa3c5ed653758fbd05509ba5b337f 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -464,6 +464,8 @@ static void __init kvm_s390_cpu_feat_init(void)
 		allow_cpu_feat(KVM_S390_VM_CPU_FEAT_IBS);
 	if (sclp.has_kss)
 		allow_cpu_feat(KVM_S390_VM_CPU_FEAT_KSS);
+	if (sclp.has_astfleie2)
+		allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ASTFLEIE2);
 	/*
 	 * KVM_S390_VM_CPU_FEAT_SKEY: Wrong shadow of PTE.I bits will make
 	 * all skey handling functions read/set the skey from the PGSTE
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 3a90d4011bf06c35416ca2ea81eab1f0f71e8be4..4396abeb58ed577c49fa9b98de1c630d6759e9a2 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -65,9 +65,9 @@ struct vsie_page {
 	 * looked up by other CPUs.
 	 */
 	unsigned long flags;			/* 0x0260 */
-	__u8 reserved[0x0700 - 0x0268];		/* 0x0268 */
-	struct kvm_s390_crypto_cb crycb;	/* 0x0700 */
-	__u8 fac[S390_ARCH_FAC_LIST_SIZE_BYTE];	/* 0x0800 */
+	__u8 reserved[0x06f8 - 0x0268];		/* 0x0268 */
+	struct kvm_s390_crypto_cb crycb;	/* 0x06f8 */
+	__u8 fac[8 + S390_ARCH_FAC_LIST_SIZE_BYTE];/* 0x0800 */
 };
 
 /**
@@ -1028,6 +1028,29 @@ static int handle_stfle_0(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
 	return 0;
 }
 
+static int handle_stfle_2(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
+			  u32 fac_list_origin)
+{
+	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+	u8 *shadow_fac = &vsie_page->fac[0];
+	u64 len;
+
+	if (read_guest_real(vcpu, fac_list_origin, &len, sizeof(len)))
+		return set_validity_icpt(scb_s, 0x1090U);
+	fac_list_origin += sizeof(len);
+	len = (len & 0xff);
+	memcpy(shadow_fac, &len, sizeof(len)); /* discard reserved bits */
+	shadow_fac += sizeof(len);
+	len += 1;
+	/* assert no overflow with maximum len */
+	BUILD_BUG_ON(sizeof(vsie_page->fac) < 257 * sizeof(u64));
+	if (read_guest_real(vcpu, fac_list_origin, shadow_fac, len * sizeof(u64)))
+		return set_validity_icpt(scb_s, 0x1090U);
+	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct vsie_page, fac), 8));
+	scb_s->fac = (u32)virt_to_phys(&vsie_page->fac) | 2;
+	return 0;
+}
+
 /*
  * Try to shadow + enable the guest 2 provided facility list.
  * Retry instruction execution if enabled for and provided by guest 2.
@@ -1057,9 +1080,11 @@ static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		case 0:
 			return handle_stfle_0(vcpu, vsie_page, fac_list_origin);
 		case 1:
+			return set_validity_icpt(&vsie_page->scb_s, 0x1330U);
 		case 2:
+			return handle_stfle_2(vcpu, vsie_page, fac_list_origin);
 		case 3:
-			unreachable();
+			return set_validity_icpt(&vsie_page->scb_s, 0x1330U);
 		}
 	}
 	return 0;

-- 
2.53.0

Re: [PATCH 2/4] s390/sclp: Detect ASTFLEIE 2 facility

[Janosch Frank]

On 2/12/26 10:24, Christoph Schlameuss wrote:
> From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> 
> Detect alternate STFLE interpretive execution facility 2.
> 
> 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>

> ---
>   arch/s390/include/asm/sclp.h   | 1 +
>   drivers/s390/char/sclp_early.c | 4 +++-
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/sclp.h b/arch/s390/include/asm/sclp.h
> index 0f184dbdbe5e0748fcecbca38b9e55a56968dc79..0f21501d3e866338895caeed385aa4f586384d69 100644
> --- a/arch/s390/include/asm/sclp.h
> +++ b/arch/s390/include/asm/sclp.h
> @@ -104,6 +104,7 @@ struct sclp_info {
>   	unsigned char has_aisii : 1;
>   	unsigned char has_aeni : 1;
>   	unsigned char has_aisi : 1;
> +	unsigned char has_astfleie2 : 1;
>   	unsigned int ibc;
>   	unsigned int mtid;
>   	unsigned int mtid_cp;
> diff --git a/drivers/s390/char/sclp_early.c b/drivers/s390/char/sclp_early.c
> index 6bf501ad8ff0ea6d3df0a721f29fd24506409493..22dd797e62291fef087d46ac1c7f805486e3935b 100644
> --- a/drivers/s390/char/sclp_early.c
> +++ b/drivers/s390/char/sclp_early.c
> @@ -61,8 +61,10 @@ static void __init sclp_early_facilities_detect(void)
>   		sclp.has_sipl = !!(sccb->cbl & 0x4000);
>   		sclp.has_sipl_eckd = !!(sccb->cbl & 0x2000);
>   	}
> -	if (sccb->cpuoff > 139)
> +	if (sccb->cpuoff > 139) {
>   		sclp.has_diag324 = !!(sccb->byte_139 & 0x80);
> +		sclp.has_astfleie2 = !!(sccb->byte_139 & 0x40);
> +	}
>   	sclp.rnmax = sccb->rnmax ? sccb->rnmax : sccb->rnmax2;
>   	sclp.rzm = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;
>   	sclp.rzm <<= 20;
> 

Re: [PATCH 3/4] KVM: s390: vsie: Refactor handle_stfle

[Janosch Frank]

On 2/12/26 10:24, Christoph Schlameuss wrote:
> From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> 
> Use switch case in anticipation of handling format-1 and format-2
> facility list designations in the future.
> As the alternate STFLE facilities are not enabled, only case 0 is
> possible.
> No functional change intended.
> 
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>

[...]

>   /*
>    * Try to shadow + enable the guest 2 provided facility list.
>    * Retry instruction execution if enabled for and provided by guest 2.
> @@ -1017,29 +1037,30 @@ static void retry_vsie_icpt(struct vsie_page *vsie_page)
>    */
>   static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>   {
> -	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> -	__u32 fac = READ_ONCE(vsie_page->scb_o->fac);
> +	u32 fac = READ_ONCE(vsie_page->scb_o->fac);
> +	int fac_list_format_mask, fac_list_format;
> +	u32 fac_list_origin;
> +	bool has_astfleie2;

I hate the fact that we called the fld "fac", we have names for that 
field and the parts that it consists of.

Drop the "fac_list_" prefix.
Pull the test_kvm_cpu_feat() up and directly assign has_astfleie2 so 
that the code below is more readable.


Code looks fine to me though

>   
> -	/*
> -	 * Alternate-STFLE-Interpretive-Execution facilities are not supported
> -	 * -> format-0 flcb
> -	 */
> +	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct vsie_page, fac), 8));
>   	if (fac && test_kvm_facility(vcpu->kvm, 7)) {
>   		retry_vsie_icpt(vsie_page);
>   		/*
>   		 * The facility list origin (FLO) is in bits 1 - 28 of the FLD
>   		 * so we need to mask here before reading.
>   		 */
> -		fac = fac & 0x7ffffff8U;
> -		/*
> -		 * format-0 -> size of nested guest's facility list == guest's size
> -		 * guest's size == host's size, since STFLE is interpretatively executed
> -		 * using a format-0 for the guest, too.
> -		 */
> -		if (read_guest_real(vcpu, fac, &vsie_page->fac,
> -				    stfle_size() * sizeof(u64)))
> -			return set_validity_icpt(scb_s, 0x1090U);
> -		scb_s->fac = (u32)virt_to_phys(&vsie_page->fac);
> +		fac_list_origin = fac & 0x7ffffff8U;
> +		has_astfleie2 = test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_ASTFLEIE2);
> +		fac_list_format_mask = has_astfleie2 ? 3 : 0;
> +		fac_list_format = fac & fac_list_format_mask;
> +		switch (fac_list_format) {
> +		case 0:
> +			return handle_stfle_0(vcpu, vsie_page, fac_list_origin);
> +		case 1:
> +		case 2:
> +		case 3:
> +			unreachable();
> +		}
>   	}
>   	return 0;
>   }
> 

Re: [PATCH 4/4] KVM: s390: vsie: Implement ASTFLEIE facility 2

[Janosch Frank]

On 2/12/26 10:24, Christoph Schlameuss wrote:
> From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> 
> Implement shadowing of format-2 facility list when running in VSIE.
> 
> ASTFLEIE2 is available since IBM z16.
> To function G1 has to run this KVM code and G1 and G2 have to run QEMU
> with ASTFLEIE2 support.
> 
> 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>
> ---

[...]

> +static int handle_stfle_2(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
> +			  u32 fac_list_origin)
> +{
> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> +	u8 *shadow_fac = &vsie_page->fac[0];
> +	u64 len;
> +
> +	if (read_guest_real(vcpu, fac_list_origin, &len, sizeof(len)))
> +		return set_validity_icpt(scb_s, 0x1090U);
> +	fac_list_origin += sizeof(len);
> +	len = (len & 0xff);
> +	memcpy(shadow_fac, &len, sizeof(len)); /* discard reserved bits */
> +	shadow_fac += sizeof(len);

You can choose between adding a struct for the new format and what you 
did here. Is this really the better option?


Add the struct and add a constant for the format 2 format control used 
in the second to last line of this function while you're at it.

> +	len += 1;
> +	/* assert no overflow with maximum len */
> +	BUILD_BUG_ON(sizeof(vsie_page->fac) < 257 * sizeof(u64));> +	if (read_guest_real(vcpu, fac_list_origin, shadow_fac, len * 
sizeof(u64)))
> +		return set_validity_icpt(scb_s, 0x1090U);

Sprinkle in some \n between the build bugs and code or just move them to 
the top as one block.
I'd much rather have build bugs at the top of the function than inside 
the code.

> +	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct vsie_page, fac), 8));

That was already added last patch, no?

> +	scb_s->fac = (u32)virt_to_phys(&vsie_page->fac) | 2;
> +	return 0;
> +}
> +
>   /*
>    * Try to shadow + enable the guest 2 provided facility list.
>    * Retry instruction execution if enabled for and provided by guest 2.
> @@ -1057,9 +1080,11 @@ static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>   		case 0:
>   			return handle_stfle_0(vcpu, vsie_page, fac_list_origin);
>   		case 1:
> +			return set_validity_icpt(&vsie_page->scb_s, 0x1330U);
>   		case 2:
> +			return handle_stfle_2(vcpu, vsie_page, fac_list_origin);
>   		case 3:
> -			unreachable();
> +			return set_validity_icpt(&vsie_page->scb_s, 0x1330U);
>   		}
>   	}
>   	return 0;
> 

Re: [PATCH 4/4] KVM: s390: vsie: Implement ASTFLEIE facility 2

[Christoph Schlameuss]

On Fri Feb 20, 2026 at 11:07 AM CET, Janosch Frank wrote:
> On 2/12/26 10:24, Christoph Schlameuss wrote:
>> From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
>> 
>> Implement shadowing of format-2 facility list when running in VSIE.
>> 
>> ASTFLEIE2 is available since IBM z16.
>> To function G1 has to run this KVM code and G1 and G2 have to run QEMU
>> with ASTFLEIE2 support.
>> 
>> 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>
>> ---
>
> [...]
>
>> +static int handle_stfle_2(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
>> +			  u32 fac_list_origin)
>> +{
>> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
>> +	u8 *shadow_fac = &vsie_page->fac[0];
>> +	u64 len;
>> +
>> +	if (read_guest_real(vcpu, fac_list_origin, &len, sizeof(len)))
>> +		return set_validity_icpt(scb_s, 0x1090U);
>> +	fac_list_origin += sizeof(len);
>> +	len = (len & 0xff);
>> +	memcpy(shadow_fac, &len, sizeof(len)); /* discard reserved bits */
>> +	shadow_fac += sizeof(len);
>
> You can choose between adding a struct for the new format and what you 
> did here. Is this really the better option?
>
>
> Add the struct and add a constant for the format 2 format control used 
> in the second to last line of this function while you're at it.
>

Will do.

>> +	len += 1;
>> +	/* assert no overflow with maximum len */
>> +	BUILD_BUG_ON(sizeof(vsie_page->fac) < 257 * sizeof(u64));> +	if (read_guest_real(vcpu, fac_list_origin, shadow_fac, len * 
> sizeof(u64)))
>> +		return set_validity_icpt(scb_s, 0x1090U);
>
> Sprinkle in some \n between the build bugs and code or just move them to 
> the top as one block.
> I'd much rather have build bugs at the top of the function than inside 
> the code.
>
>> +	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct vsie_page, fac), 8));
>
> That was already added last patch, no?
>

Yes, it was. Keeping the one in handle_stfle(). We actually can put both newly
introduced build bug macros there.

>> +	scb_s->fac = (u32)virt_to_phys(&vsie_page->fac) | 2;
>> +	return 0;
>> +}
>> +
>>   /*
>>    * Try to shadow + enable the guest 2 provided facility list.
>>    * Retry instruction execution if enabled for and provided by guest 2.
>> @@ -1057,9 +1080,11 @@ static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>   		case 0:
>>   			return handle_stfle_0(vcpu, vsie_page, fac_list_origin);
>>   		case 1:
>> +			return set_validity_icpt(&vsie_page->scb_s, 0x1330U);
>>   		case 2:
>> +			return handle_stfle_2(vcpu, vsie_page, fac_list_origin);
>>   		case 3:
>> -			unreachable();
>> +			return set_validity_icpt(&vsie_page->scb_s, 0x1330U);
>>   		}
>>   	}
>>   	return 0;
>> 

Re: [PATCH 2/4] s390/sclp: Detect ASTFLEIE 2 facility

[Hendrik Brueckner]

On Thu, Feb 12, 2026 at 10:24:56AM +0100, Christoph Schlameuss wrote:
> From: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> 
> Detect alternate STFLE interpretive execution facility 2.
> 
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
> ---
>  arch/s390/include/asm/sclp.h   | 1 +
>  drivers/s390/char/sclp_early.c | 4 +++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 

Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>