kvm: encapsulate HAS_DEVICE for vm attrs

More and more virtual machine specifics between kvm and qemu will be
transferred with vm attributes.
So we encapsulate the common logic in a generic function.

Additionally we need only to check during initialization if kvm supports
virtual machine attributes.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: NThomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: NThomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: NJens Freimann <jfrei@linux.vnet.ibm.com>
Message-Id: <1426164834-38648-2-git-send-email-jfrei@linux.vnet.ibm.com>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>

include/sysemu/kvm.h

@@ -224,6 +224,18 @@ int kvm_vcpu_ioctl(CPUState *cpu, int type, ...);
  */
 int kvm_device_ioctl(int fd, int type, ...);
 
+/**
+ * kvm_vm_check_attr - check for existence of a specific vm attribute
+ * @s: The KVMState pointer
+ * @group: the group
+ * @attr: the attribute of that group to query for
+ *
+ * Returns: 1 if the attribute exists
+ *          0 if the attribute either does not exist or if the vm device
+ *            interface is unavailable
+ */
+int kvm_vm_check_attr(KVMState *s, uint32_t group, uint64_t attr);
+
 /**
  * kvm_create_device - create a KVM device for the device control API
  * @KVMState: The KVMState pointer

kvm-all.c

@@ -126,6 +126,7 @@ bool kvm_gsi_routing_allowed;
 bool kvm_gsi_direct_mapping;
 bool kvm_allowed;
 bool kvm_readonly_mem_allowed;
+bool kvm_vm_attributes_allowed;
 
 static const KVMCapabilityInfo kvm_required_capabilites[] = {
     KVM_CAP_INFO(USER_MEMORY),
@@ -1598,6 +1599,9 @@ static int kvm_init(MachineState *ms)
     kvm_resamplefds_allowed =
         (kvm_check_extension(s, KVM_CAP_IRQFD_RESAMPLE) > 0);
 
+    kvm_vm_attributes_allowed =
+        (kvm_check_extension(s, KVM_CAP_VM_ATTRIBUTES) > 0);
+
     ret = kvm_arch_init(ms, s);
     if (ret < 0) {
         goto err;
@@ -1936,6 +1940,23 @@ int kvm_device_ioctl(int fd, int type, ...)
     return ret;
 }
 
+int kvm_vm_check_attr(KVMState *s, uint32_t group, uint64_t attr)
+{
+    int ret;
+    struct kvm_device_attr attribute = {
+        .group = group,
+        .attr = attr,
+    };
+
+    if (!kvm_vm_attributes_allowed) {
+        return 0;
+    }
+
+    ret = kvm_vm_ioctl(s, KVM_HAS_DEVICE_ATTR, &attribute);
+    /* kvm returns 0 on success for HAS_DEVICE_ATTR */
+    return ret ? 0 : 1;
+}
+
 int kvm_has_sync_mmu(void)
 {
     return kvm_check_extension(kvm_state, KVM_CAP_SYNC_MMU);