[Qemu-devel] [PATCH v3 16/22] memory-device: add optional function get_device_id()

[David Hildenbrand]

When reporting the id of virtio-based memory devices, we always have to
take the one of the proxy device (parent), not the one of the memory
device directly.

Let's generalize this by allowing memory devices to specify an optional
"get_device_id" function. This id can then be used to report errors to the
user from memory-device.c code, without having to special case e.g.
virtio devices.

While at it, properly treat id == NULL and report "(unnamed)" instead.

Details:

When the user creates a virtio device (e.g.  virtio-balloon-pci), two
devices are actually created.

1. Virtio proxy device (e.g. TYPE_VIRTIO_BALLOON_PCI)
2. The "real" virtio device (e.g. TYPE_VIRTIO_BALLOON).

1. aliases all properties of 2, so 2. can be properly configured using 1.
1. gets the device ID set specified by the user. 2. gets no ID set.

If we want to make 2. a MemoryDevice but report errors/information to the
user, we always have to report the id of 1. (because that's the device the
user instantiated and configured).

Signed-off-by: David Hildenbrand <address@hidden>
---
 hw/mem/memory-device.c         | 7 +++++--
 include/hw/mem/memory-device.h | 4 ++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
index 534bd38313..92878fc327 100644
--- a/hw/mem/memory-device.c
+++ b/hw/mem/memory-device.c
@@ -174,8 +174,11 @@ static uint64_t memory_device_get_free_addr(MachineState 
*ms,
 
         if (ranges_overlap(md_addr, md_size, new_addr, size)) {
             if (hint) {
-                const DeviceState *d = DEVICE(md);
-                error_setg(errp, "address range conflicts with '%s'", d->id);
+                const char *id = mdc->get_device_id ? mdc->get_device_id(md) :
+                                 DEVICE(md)->id;
+
+                error_setg(errp, "address range conflicts with '%s'",
+                           id ? id : "(unnamed)");
                 goto out;
             }
             new_addr = QEMU_ALIGN_UP(md_addr + md_size, align);
diff --git a/include/hw/mem/memory-device.h b/include/hw/mem/memory-device.h
index fd0b43c224..66143cffc6 100644
--- a/include/hw/mem/memory-device.h
+++ b/include/hw/mem/memory-device.h
@@ -42,6 +42,9 @@ typedef struct MemoryDeviceState {
  * of multiple successive memory regions, a covering memory region is to
  * be used. Scattered memory regions are not supported for single devices.
  * @fill_device_info: Translate current @md state into #MemoryDeviceInfo.
+ * @get_device_id: Optional. Allows memory devices behind proxy devices
+ * (e.g. virtio based) to report the id of the proxy device to the user
+ * instead of the (empty) id of the memory device.
  */
 typedef struct MemoryDeviceClass {
     /* private */
@@ -54,6 +57,7 @@ typedef struct MemoryDeviceClass {
     MemoryRegion *(*get_memory_region)(MemoryDeviceState *md, Error **errp);
     void (*fill_device_info)(const MemoryDeviceState *md,
                              MemoryDeviceInfo *info);
+    const char *(*get_device_id)(const MemoryDeviceState *md);
 } MemoryDeviceClass;
 
 MemoryDeviceInfoList *qmp_memory_device_list(void);
-- 
2.17.1