s390x/kvm: disable host model for problematic compat machines

Compatibility machines that touch runtime-instrumentation should not
be used with the CPU model. Otherwise the host model will look different,
depending on the QEMU machine QEMU has been started with.

So let's simply disable the host model for existing compatibility machines
that all disable ri. This, in return, disables the CPU model for these
compat machines completely.

Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Message-Id: <20160905085244.99980-23-dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index bbf8b2a..d40ef09 100644 (file)
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -2481,6 +2481,10 @@ static int configure_cpu_feat(const S390FeatBitmap features)
 
 bool kvm_s390_cpu_models_supported(void)
 {
+    if (!ri_allowed()) {
+        /* compatibility machines interfere with the cpu model */
+        return false;
+    }
     return kvm_vm_check_attr(kvm_state, KVM_S390_VM_CPU_MODEL,
                              KVM_S390_VM_CPU_MACHINE) &&
            kvm_vm_check_attr(kvm_state, KVM_S390_VM_CPU_MODEL,