[Qemu-devel] [PATCH v2 2/2] hw/acpi/vmgenid: prevent more than one vmgenid device

[Laszlo Ersek <lersek@redhat.com>]

A system with multiple VMGENID devices is undefined in the VMGENID spec by
omission.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Ben Warren <ben@skyportsystems.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v2:
    - use find_vmgenid_dev() rather than open-code
      object_resolve_path_type() [Michael]
    - add comments to both the definition of find_vmgenid_dev() and its call
      site in vmgenid_realize() [Michael]

 include/hw/acpi/vmgenid.h | 1 +
 hw/acpi/vmgenid.c         | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/hw/acpi/vmgenid.h b/include/hw/acpi/vmgenid.h
index 8578476baebe..7beb9592fb01 100644
--- a/include/hw/acpi/vmgenid.h
+++ b/include/hw/acpi/vmgenid.h
@@ -24,6 +24,7 @@ typedef struct VmGenIdState {
     bool write_pointer_available;
 } VmGenIdState;
 
+/* returns NULL unless there is exactly one device */
 static inline Object *find_vmgenid_dev(void)
 {
     return object_resolve_path_type("", VMGENID_DEVICE, NULL);
diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
index c3ddcc8e7cb0..a32b847fe0df 100644
--- a/hw/acpi/vmgenid.c
+++ b/hw/acpi/vmgenid.c
@@ -221,6 +221,14 @@ static void vmgenid_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    /* Given that this function is executing, there is at least one VMGENID
+     * device. Check if there are several.
+     */
+    if (!find_vmgenid_dev()) {
+        error_setg(errp, "at most one %s device is permitted", VMGENID_DEVICE);
+        return;
+    }
+
     qemu_register_reset(vmgenid_handle_reset, vms);
 }
 
-- 
2.9.3