s390: guest support for diagnose 0x318

DIAGNOSE 0x318 (diag318) is an s390 instruction that allows the storage
of diagnostic information that is collected by the firmware in the case
of hardware/firmware service events.

QEMU handles the instruction by storing the info in the CPU state. A
subsequent register sync will communicate the data to the hypervisor.

QEMU handles the migration via a VM State Description.

This feature depends on the Extended-Length SCCB (els) feature. If
els is not present, then a warning will be printed and the SCLP bit
that allows the Linux kernel to execute the instruction will not be
set.

Availability of this instruction is determined by byte 134 (aka fac134)
bit 0 of the SCLP Read Info block. This coincidentally expands into the
space used for CPU entries, which means VMs running with the diag318
capability may not be able to read information regarding all CPUs
unless the guest kernel supports an extended-length SCCB.

This feature is not supported in protected virtualization mode.

Signed-off-by: Collin Walling <walling@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-Id: <20200915194416.107460-9-walling@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

hw/s390x/sclp.c

@@ -139,6 +139,11 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
     s390_get_feat_block(S390_FEAT_TYPE_SCLP_CONF_CHAR_EXT,
                          read_info->conf_char_ext);
 
+    if (s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB)) {
+        s390_get_feat_block(S390_FEAT_TYPE_SCLP_FAC134,
+                            &read_info->fac134);
+    }
+
     read_info->facilities = cpu_to_be64(SCLP_HAS_CPU_INFO |
                                         SCLP_HAS_IOA_RECONFIG);
 

include/hw/s390x/sclp.h

@@ -134,7 +134,15 @@ typedef struct ReadInfo {
     uint16_t highest_cpu;
     uint8_t  _reserved5[124 - 122];     /* 122-123 */
     uint32_t hmfai;
+    uint8_t  _reserved7[134 - 128];     /* 128-133 */
+    uint8_t  fac134;
+    uint8_t  _reserved8[144 - 135];     /* 135-143 */
     struct CPUEntry entries[];
+    /*
+     * When the Extended-Length SCCB (ELS) feature is enabled the
+     * start of the entries field begins at an offset denoted by the
+     * offset_cpu field, otherwise it's at an offset of 128.
+     */
 } QEMU_PACKED ReadInfo;
 
 typedef struct ReadCpuInfo {

target/s390x/cpu.h

@@ -112,6 +112,8 @@ struct CPUS390XState {
     uint16_t external_call_addr;
     DECLARE_BITMAP(emergency_signals, S390_MAX_CPUS);
 
+    uint64_t diag318_info;
+
     /* Fields up to this point are cleared by a CPU reset */
     struct {} end_reset_fields;
 

target/s390x/cpu_features.h

@@ -23,6 +23,7 @@ typedef enum {
     S390_FEAT_TYPE_STFL,
     S390_FEAT_TYPE_SCLP_CONF_CHAR,
     S390_FEAT_TYPE_SCLP_CONF_CHAR_EXT,
+    S390_FEAT_TYPE_SCLP_FAC134,
     S390_FEAT_TYPE_SCLP_CPU,
     S390_FEAT_TYPE_MISC,
     S390_FEAT_TYPE_PLO,

target/s390x/cpu_features_def.h.inc

@@ -122,6 +122,9 @@ DEF_FEAT(SIE_CMMA, "cmma", SCLP_CONF_CHAR_EXT, 1, "SIE: Collaborative-memory-man
 DEF_FEAT(SIE_PFMFI, "pfmfi", SCLP_CONF_CHAR_EXT, 9, "SIE: PFMF interpretation facility")
 DEF_FEAT(SIE_IBS, "ibs", SCLP_CONF_CHAR_EXT, 10, "SIE: Interlock-and-broadcast-suppression facility")
 
+/* Features exposed via SCLP SCCB Facilities byte 134 (bit numbers relative to byte-134) */
+DEF_FEAT(DIAG_318, "diag318", SCLP_FAC134, 0, "Control program name and version codes")
+
 /* Features exposed via SCLP CPU info. */
 DEF_FEAT(SIE_F2, "sief2", SCLP_CPU, 4, "SIE: interception format 2 (Virtual SIE)")
 DEF_FEAT(SIE_SKEY, "skey", SCLP_CPU, 5, "SIE: Storage-key facility")

target/s390x/cpu_models.c

@@ -824,6 +824,7 @@ static void check_consistency(const S390CPUModel *model)
         { S390_FEAT_PTFF_STOE, S390_FEAT_MULTIPLE_EPOCH },
         { S390_FEAT_PTFF_STOUE, S390_FEAT_MULTIPLE_EPOCH },
         { S390_FEAT_AP_QUEUE_INTERRUPT_CONTROL, S390_FEAT_AP },
+        { S390_FEAT_DIAG_318, S390_FEAT_EXTENDED_LENGTH_SCCB },
     };
     int i;
 

target/s390x/gen-features.c

@@ -523,6 +523,7 @@ static uint16_t full_GEN12_GA1[] = {
     S390_FEAT_AP_FACILITIES_TEST,
     S390_FEAT_AP,
     S390_FEAT_EXTENDED_LENGTH_SCCB,
+    S390_FEAT_DIAG_318,
 };
 
 static uint16_t full_GEN12_GA2[] = {

target/s390x/kvm.c

@@ -105,6 +105,7 @@
 
 #define DIAG_TIMEREVENT                 0x288
 #define DIAG_IPL                        0x308
+#define DIAG_SET_CONTROL_PROGRAM_CODES  0x318
 #define DIAG_KVM_HYPERCALL              0x500
 #define DIAG_KVM_BREAKPOINT             0x501
 
@@ -602,6 +603,11 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_ETOKEN;
     }
 
+    if (can_sync_regs(cs, KVM_SYNC_DIAG318)) {
+        cs->kvm_run->s.regs.diag318 = env->diag318_info;
+        cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_DIAG318;
+    }
+
     /* Finally the prefix */
     if (can_sync_regs(cs, KVM_SYNC_PREFIX)) {
         cs->kvm_run->s.regs.prefix = env->psa;
@@ -741,6 +747,10 @@ int kvm_arch_get_registers(CPUState *cs)
         }
     }
 
+    if (can_sync_regs(cs, KVM_SYNC_DIAG318)) {
+        env->diag318_info = cs->kvm_run->s.regs.diag318;
+    }
+
     return 0;
 }
 
@@ -1601,6 +1611,27 @@ static int handle_sw_breakpoint(S390CPU *cpu, struct kvm_run *run)
     return -ENOENT;
 }
 
+static void handle_diag_318(S390CPU *cpu, struct kvm_run *run)
+{
+    uint64_t reg = (run->s390_sieic.ipa & 0x00f0) >> 4;
+    uint64_t diag318_info = run->s.regs.gprs[reg];
+
+    /*
+     * DIAG 318 can only be enabled with KVM support. As such, let's
+     * ensure a guest cannot execute this instruction erroneously.
+     */
+    if (!s390_has_feat(S390_FEAT_DIAG_318)) {
+        kvm_s390_program_interrupt(cpu, PGM_SPECIFICATION);
+    }
+
+    cpu->env.diag318_info = diag318_info;
+
+    if (can_sync_regs(CPU(cpu), KVM_SYNC_DIAG318)) {
+        run->s.regs.diag318 = diag318_info;
+        run->kvm_dirty_regs |= KVM_SYNC_DIAG318;
+    }
+}
+
 #define DIAG_KVM_CODE_MASK 0x000000000000ffff
 
 static int handle_diag(S390CPU *cpu, struct kvm_run *run, uint32_t ipb)
@@ -1620,6 +1651,9 @@ static int handle_diag(S390CPU *cpu, struct kvm_run *run, uint32_t ipb)
     case DIAG_IPL:
         kvm_handle_diag_308(cpu, run);
         break;
+    case DIAG_SET_CONTROL_PROGRAM_CODES:
+        handle_diag_318(cpu, run);
+        break;
     case DIAG_KVM_HYPERCALL:
         r = handle_hypercall(cpu, run);
         break;
@@ -2464,6 +2498,11 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
      */
     set_bit(S390_FEAT_EXTENDED_LENGTH_SCCB, model->features);
 
+    /* DIAGNOSE 0x318 is not supported under protected virtualization */
+    if (!s390_is_pv() && kvm_check_extension(kvm_state, KVM_CAP_S390_DIAG318)) {
+        set_bit(S390_FEAT_DIAG_318, model->features);
+    }
+
     /* strip of features that are not part of the maximum model */
     bitmap_and(model->features, model->features, model->def->full_feat,
                S390_FEAT_MAX);

target/s390x/machine.c

@@ -234,6 +234,22 @@ const VMStateDescription vmstate_etoken = {
     }
 };
 
+static bool diag318_needed(void *opaque)
+{
+    return s390_has_feat(S390_FEAT_DIAG_318);
+}
+
+const VMStateDescription vmstate_diag318 = {
+    .name = "cpu/diag318",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = diag318_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(env.diag318_info, S390CPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 const VMStateDescription vmstate_s390_cpu = {
     .name = "cpu",
     .post_load = cpu_post_load,
@@ -270,6 +286,7 @@ const VMStateDescription vmstate_s390_cpu = {
         &vmstate_gscb,
         &vmstate_bpbc,
         &vmstate_etoken,
+        &vmstate_diag318,
         NULL
     },
 };