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From e1a3684f9b08fa9db35331b5c5ad11879f512e90 Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Wed, 11 Nov 2020 12:03:11 -0500
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Subject: [PATCH 11/18] s390/sclp: add extended-length sccb support for kvm
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 guest
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RH-Author: Thomas Huth <thuth@redhat.com>
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Message-id: <20201111120316.707489-8-thuth@redhat.com>
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Patchwork-id: 99504
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O-Subject: [RHEL-8.4.0 qemu-kvm PATCH v2 07/12] s390/sclp: add extended-length sccb support for kvm guest
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Bugzilla: 1798506
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RH-Acked-by: Jens Freimann <jfreimann@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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From: Collin Walling <walling@linux.ibm.com>
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As more features and facilities are added to the Read SCP Info (RSCPI)
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response, more space is required to store them. The space used to store
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these new features intrudes on the space originally used to store CPU
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entries. This means as more features and facilities are added to the
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RSCPI response, less space can be used to store CPU entries.
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With the Extended-Length SCCB (ELS) facility, a KVM guest can execute
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the RSCPI command and determine if the SCCB is large enough to store a
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complete reponse. If it is not large enough, then the required length
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will be set in the SCCB header.
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The caller of the SCLP command is responsible for creating a
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large-enough SCCB to store a complete response. Proper checking should
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be in place, and the caller should execute the command once-more with
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the large-enough SCCB.
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This facility also enables an extended SCCB for the Read CPU Info
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(RCPUI) command.
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When this facility is enabled, the boundary violation response cannot
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be a result from the RSCPI, RSCPI Forced, or RCPUI commands.
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In order to tolerate kernels that do not yet have full support for this
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feature, a "fixed" offset to the start of the CPU Entries within the
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Read SCP Info struct is set to allow for the original 248 max entries
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when this feature is disabled.
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Additionally, this is introduced as a CPU feature to protect the guest
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from migrating to a machine that does not support storing an extended
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SCCB. This could otherwise hinder the VM from being able to read all
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available CPU entries after migration (such as during re-ipl).
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Signed-off-by: Collin Walling <walling@linux.ibm.com>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Acked-by: Cornelia Huck <cohuck@redhat.com>
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Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
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Message-Id: <20200915194416.107460-7-walling@linux.ibm.com>
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Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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(cherry picked from commit 1ecd6078f587cfadda8edc93d45b5072e35f2d17)
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 hw/s390x/sclp.c                     | 43 +++++++++++++++++++++++++----
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 include/hw/s390x/sclp.h             |  1 +
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 target/s390x/cpu_features_def.inc.h |  1 +
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 target/s390x/gen-features.c         |  1 +
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 target/s390x/kvm.c                  |  8 ++++++
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 5 files changed, 48 insertions(+), 6 deletions(-)
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diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
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index 017989b3888..8d111628e04 100644
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--- a/hw/s390x/sclp.c
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+++ b/hw/s390x/sclp.c
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@@ -49,13 +49,30 @@ static inline bool sclp_command_code_valid(uint32_t code)
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     return false;
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 }
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-static bool sccb_verify_boundary(uint64_t sccb_addr, uint16_t sccb_len)
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+static bool sccb_verify_boundary(uint64_t sccb_addr, uint16_t sccb_len,
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+                                 uint32_t code)
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 {
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     uint64_t sccb_max_addr = sccb_addr + sccb_len - 1;
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     uint64_t sccb_boundary = (sccb_addr & PAGE_MASK) + PAGE_SIZE;
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-    if (sccb_max_addr < sccb_boundary) {
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-        return true;
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+    switch (code & SCLP_CMD_CODE_MASK) {
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+    case SCLP_CMDW_READ_SCP_INFO:
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+    case SCLP_CMDW_READ_SCP_INFO_FORCED:
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+    case SCLP_CMDW_READ_CPU_INFO:
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+        /*
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+         * An extended-length SCCB is only allowed for Read SCP/CPU Info and
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+         * is allowed to exceed the 4k boundary. The respective commands will
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+         * set the length field to the required length if an insufficient
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+         * SCCB length is provided.
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+         */
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+        if (s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB)) {
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+            return true;
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+        }
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+        /* fallthrough */
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+    default:
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+        if (sccb_max_addr < sccb_boundary) {
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+            return true;
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+        }
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     }
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     return false;
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@@ -80,6 +97,12 @@ static void prepare_cpu_entries(MachineState *ms, CPUEntry *entry, int *count)
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 #define SCCB_REQ_LEN(s, max_cpus) (sizeof(s) + max_cpus * sizeof(CPUEntry))
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+static inline bool ext_len_sccb_supported(SCCBHeader header)
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+{
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+    return s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) &&
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+           header.control_mask[2] & SCLP_VARIABLE_LENGTH_RESPONSE;
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+}
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+
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 /* Provide information about the configuration, CPUs and storage */
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 static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
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 {
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@@ -89,10 +112,15 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
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     int rnsize, rnmax;
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     IplParameterBlock *ipib = s390_ipl_get_iplb();
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     int required_len = SCCB_REQ_LEN(ReadInfo, machine->possible_cpus->len);
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-    int offset_cpu = offsetof(ReadInfo, entries);
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+    int offset_cpu = s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) ?
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+                     offsetof(ReadInfo, entries) :
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+                     SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET;
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     CPUEntry *entries_start = (void *)sccb + offset_cpu;
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     if (be16_to_cpu(sccb->h.length) < required_len) {
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+        if (ext_len_sccb_supported(sccb->h)) {
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+            sccb->h.length = cpu_to_be16(required_len);
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+        }
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         sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
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         return;
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     }
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@@ -153,6 +181,9 @@ static void sclp_read_cpu_info(SCLPDevice *sclp, SCCB *sccb)
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     int required_len = SCCB_REQ_LEN(ReadCpuInfo, machine->possible_cpus->len);
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     if (be16_to_cpu(sccb->h.length) < required_len) {
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+        if (ext_len_sccb_supported(sccb->h)) {
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+            sccb->h.length = cpu_to_be16(required_len);
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+        }
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         sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
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         return;
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     }
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@@ -249,7 +280,7 @@ int sclp_service_call_protected(CPUS390XState *env, uint64_t sccb,
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         goto out_write;
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     }
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-    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length))) {
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+    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length), code)) {
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         work_sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
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         goto out_write;
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     }
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@@ -302,7 +333,7 @@ int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
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         goto out_write;
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     }
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-    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length))) {
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+    if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length), code)) {
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         work_sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
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         goto out_write;
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     }
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diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h
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index 55f53a46540..df2fa4169b0 100644
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--- a/include/hw/s390x/sclp.h
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+++ b/include/hw/s390x/sclp.h
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@@ -110,6 +110,7 @@ typedef struct CPUEntry {
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     uint8_t reserved1;
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 } QEMU_PACKED CPUEntry;
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+#define SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET     128
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 typedef struct ReadInfo {
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     SCCBHeader h;
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     uint16_t rnmax;
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diff --git a/target/s390x/cpu_features_def.inc.h b/target/s390x/cpu_features_def.inc.h
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index 60db28351d0..3548d65a69a 100644
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--- a/target/s390x/cpu_features_def.inc.h
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+++ b/target/s390x/cpu_features_def.inc.h
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@@ -97,6 +97,7 @@ DEF_FEAT(GUARDED_STORAGE, "gs", STFL, 133, "Guarded-storage facility")
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 DEF_FEAT(VECTOR_PACKED_DECIMAL, "vxpd", STFL, 134, "Vector packed decimal facility")
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 DEF_FEAT(VECTOR_ENH, "vxeh", STFL, 135, "Vector enhancements facility")
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 DEF_FEAT(MULTIPLE_EPOCH, "mepoch", STFL, 139, "Multiple-epoch facility")
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+DEF_FEAT(EXTENDED_LENGTH_SCCB, "els", STFL, 140, "Extended-length SCCB facility")
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 DEF_FEAT(TEST_PENDING_EXT_INTERRUPTION, "tpei", STFL, 144, "Test-pending-external-interruption facility")
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 DEF_FEAT(INSERT_REFERENCE_BITS_MULT, "irbm", STFL, 145, "Insert-reference-bits-multiple facility")
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 DEF_FEAT(MSA_EXT_8, "msa8-base", STFL, 146, "Message-security-assist-extension-8 facility (excluding subfunctions)")
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diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c
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index 8ddeebc5441..6857f657fba 100644
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--- a/target/s390x/gen-features.c
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+++ b/target/s390x/gen-features.c
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@@ -522,6 +522,7 @@ static uint16_t full_GEN12_GA1[] = {
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     S390_FEAT_AP_QUEUE_INTERRUPT_CONTROL,
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     S390_FEAT_AP_FACILITIES_TEST,
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     S390_FEAT_AP,
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+    S390_FEAT_EXTENDED_LENGTH_SCCB,
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 };
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 static uint16_t full_GEN12_GA2[] = {
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diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
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index 0bbf8f81b09..ef437acb5c1 100644
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--- a/target/s390x/kvm.c
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+++ b/target/s390x/kvm.c
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@@ -2441,6 +2441,14 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
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         KVM_S390_VM_CRYPTO_ENABLE_APIE)) {
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         set_bit(S390_FEAT_AP, model->features);
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     }
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+
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+    /*
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+     * Extended-Length SCCB is handled entirely within QEMU.
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+     * For PV guests this is completely fenced by the Ultravisor, as Service
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+     * Call error checking and STFLE interpretation are handled via SIE.
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+     */
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+    set_bit(S390_FEAT_EXTENDED_LENGTH_SCCB, model->features);
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+
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     /* strip of features that are not part of the maximum model */
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     bitmap_and(model->features, model->features, model->def->full_feat,
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                S390_FEAT_MAX);
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-- 
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2.27.0
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