s390x/kvm: Handle bpb feature

We need to handle the bpb control on reset and migration. Normally
stfle.82 is transparent (and the normal guest part works without
hypervisor activity). To prevent any issues we require full
host kernel support for this feature.

Cc: qemu-stable@nongnu.org
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20180118085628.40798-3-borntraeger@de.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
[CH: 'Branch Prediction Blocking' -> 'Branch prediction blocking']
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

7 files changed, 36 insertions, 0 deletions

diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
index ae3cee91a2..d2e6b9f5c7 100644
--- a/target/s390x/cpu.c
+++ b/target/s390x/cpu.c
@@ -89,6 +89,7 @@ static void s390_cpu_reset(CPUState *s)
     CPUS390XState *env = &cpu->env;
 
     env->pfault_token = -1UL;
+    env->bpbc = false;
     scc->parent_reset(s);
     cpu->env.sigp_order = 0;
     s390_cpu_set_state(CPU_STATE_STOPPED, cpu);
diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index 915bccbc75..a1123ad621 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -93,6 +93,7 @@ struct CPUS390XState {
 
     uint32_t fpc;          /* floating-point control register */
     uint32_t cc_op;
+    bool bpbc;             /* branch prediction blocking */
 
     float_status fpu_status; /* passed to softfloat lib */
 
diff --git a/target/s390x/cpu_features.c b/target/s390x/cpu_features.c
index 31a4676f05..b45ef09f93 100644
--- a/target/s390x/cpu_features.c
+++ b/target/s390x/cpu_features.c
@@ -89,6 +89,7 @@ static const S390FeatDef s390_features[] = {
     FEAT_INIT("msa4-base", S390_FEAT_TYPE_STFL, 77, "Message-security-assist-extension-4 facility (excluding subfunctions)"),
     FEAT_INIT("edat2", S390_FEAT_TYPE_STFL, 78, "Enhanced-DAT facility 2"),
     FEAT_INIT("dfppc", S390_FEAT_TYPE_STFL, 80, "Decimal-floating-point packed-conversion facility"),
+    FEAT_INIT("bpb", S390_FEAT_TYPE_STFL, 82, "Branch prediction blocking"),
     FEAT_INIT("vx", S390_FEAT_TYPE_STFL, 129, "Vector facility"),
     FEAT_INIT("iep", S390_FEAT_TYPE_STFL, 130, "Instruction-execution-protection facility"),
     FEAT_INIT("sea_esop2", S390_FEAT_TYPE_STFL, 131, "Side-effect-access facility and Enhanced-suppression-on-protection facility 2"),
diff --git a/target/s390x/cpu_features_def.h b/target/s390x/cpu_features_def.h
index 4b6d4e9cc0..4487cfd53b 100644
--- a/target/s390x/cpu_features_def.h
+++ b/target/s390x/cpu_features_def.h
@@ -80,6 +80,7 @@ typedef enum {
     S390_FEAT_MSA_EXT_4,
     S390_FEAT_EDAT_2,
     S390_FEAT_DFP_PACKED_CONVERSION,
+    S390_FEAT_BPB,
     S390_FEAT_VECTOR,
     S390_FEAT_INSTRUCTION_EXEC_PROT,
     S390_FEAT_SIDE_EFFECT_ACCESS_ESOP2,
diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c
index b24f6ada5b..563aced35e 100644
--- a/target/s390x/gen-features.c
+++ b/target/s390x/gen-features.c
@@ -352,6 +352,7 @@ static uint16_t base_GEN14_GA1[] = {
  * support these features yet.
  */
 static uint16_t full_GEN7_GA1[] = {
+    S390_FEAT_BPB,
     S390_FEAT_SIE_F2,
     S390_FEAT_SIE_SKEY,
     S390_FEAT_SIE_GPERE,
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 6a18a413b4..8736001156 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -490,6 +490,11 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_GSCB;
     }
 
+    if (can_sync_regs(cs, KVM_SYNC_BPBC)) {
+        cs->kvm_run->s.regs.bpbc = env->bpbc;
+        cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_BPBC;
+    }
+
     /* Finally the prefix */
     if (can_sync_regs(cs, KVM_SYNC_PREFIX)) {
         cs->kvm_run->s.regs.prefix = env->psa;
@@ -600,6 +605,10 @@ int kvm_arch_get_registers(CPUState *cs)
         memcpy(env->gscb, cs->kvm_run->s.regs.gscb, 32);
     }
 
+    if (can_sync_regs(cs, KVM_SYNC_BPBC)) {
+        env->bpbc = cs->kvm_run->s.regs.bpbc;
+    }
+
     /* pfault parameters */
     if (can_sync_regs(cs, KVM_SYNC_PFAULT)) {
         env->pfault_token = cs->kvm_run->s.regs.pft;
@@ -2278,6 +2287,11 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
         clear_bit(S390_FEAT_CMM_NT, model->features);
     }
 
+    /* bpb needs kernel support for migration, VSIE and reset */
+    if (!kvm_check_extension(kvm_state, KVM_CAP_S390_BPB)) {
+        clear_bit(S390_FEAT_BPB, model->features);
+    }
+
     /* We emulate a zPCI bus and AEN, therefore we don't need HW support */
     if (pci_available) {
         set_bit(S390_FEAT_ZPCI, model->features);
diff --git a/target/s390x/machine.c b/target/s390x/machine.c
index b78f326d3a..84b4928755 100644
--- a/target/s390x/machine.c
+++ b/target/s390x/machine.c
@@ -194,6 +194,22 @@ const VMStateDescription vmstate_gscb = {
         }
 };
 
+static bool bpbc_needed(void *opaque)
+{
+    return s390_has_feat(S390_FEAT_BPB);
+}
+
+const VMStateDescription vmstate_bpbc = {
+    .name = "cpu/bpbc",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = bpbc_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_BOOL(env.bpbc, S390CPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 const VMStateDescription vmstate_s390_cpu = {
     .name = "cpu",
     .post_load = cpu_post_load,
@@ -228,6 +244,7 @@ const VMStateDescription vmstate_s390_cpu = {
         &vmstate_riccb,
         &vmstate_exval,
         &vmstate_gscb,
+        &vmstate_bpbc,
         NULL
     },
 };