1 files changed, 54 insertions, 0 deletions

diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
index 0eec0872a9..d37cfbd65d 100644
--- a/hw/mem/memory-device.c
+++ b/hw/mem/memory-device.c
@@ -286,6 +286,7 @@ void memory_device_plug(MemoryDeviceState *md, MachineState *ms)
     g_assert(ms->device_memory);
 
     ms->device_memory->used_region_size += memory_region_size(mr);
+    ms->device_memory->required_memslots += memory_device_get_memslots(md);
     memory_region_add_subregion(&ms->device_memory->mr,
                                 addr - ms->device_memory->base, mr);
     trace_memory_device_plug(DEVICE(md)->id ? DEVICE(md)->id : "", addr);
@@ -305,6 +306,7 @@ void memory_device_unplug(MemoryDeviceState *md, MachineState *ms)
 
     memory_region_del_subregion(&ms->device_memory->mr, mr);
     ms->device_memory->used_region_size -= memory_region_size(mr);
+    ms->device_memory->required_memslots -= memory_device_get_memslots(md);
     trace_memory_device_unplug(DEVICE(md)->id ? DEVICE(md)->id : "",
                                mdc->get_addr(md));
 }
@@ -324,6 +326,50 @@ uint64_t memory_device_get_region_size(const MemoryDeviceState *md,
     return memory_region_size(mr);
 }
 
+static void memory_devices_region_mod(MemoryListener *listener,
+                                      MemoryRegionSection *mrs, bool add)
+{
+    DeviceMemoryState *dms = container_of(listener, DeviceMemoryState,
+                                          listener);
+
+    if (!memory_region_is_ram(mrs->mr)) {
+        warn_report("Unexpected memory region mapped into device memory region.");
+        return;
+    }
+
+    /*
+     * The expectation is that each distinct RAM memory region section in
+     * our region for memory devices consumes exactly one memslot in KVM
+     * and in vhost. For vhost, this is true, except:
+     * * ROM memory regions don't consume a memslot. These get used very
+     *   rarely for memory devices (R/O NVDIMMs).
+     * * Memslots without a fd (memory-backend-ram) don't necessarily
+     *   consume a memslot. Such setups are quite rare and possibly bogus:
+     *   the memory would be inaccessible by such vhost devices.
+     *
+     * So for vhost, in corner cases we might over-estimate the number of
+     * memslots that are currently used or that might still be reserved
+     * (required - used).
+     */
+    dms->used_memslots += add ? 1 : -1;
+
+    if (dms->used_memslots > dms->required_memslots) {
+        warn_report("Memory devices use more memory slots than indicated as required.");
+    }
+}
+
+static void memory_devices_region_add(MemoryListener *listener,
+                                      MemoryRegionSection *mrs)
+{
+    return memory_devices_region_mod(listener, mrs, true);
+}
+
+static void memory_devices_region_del(MemoryListener *listener,
+                                      MemoryRegionSection *mrs)
+{
+    return memory_devices_region_mod(listener, mrs, false);
+}
+
 void machine_memory_devices_init(MachineState *ms, hwaddr base, uint64_t size)
 {
     g_assert(size);
@@ -333,8 +379,16 @@ void machine_memory_devices_init(MachineState *ms, hwaddr base, uint64_t size)
 
     memory_region_init(&ms->device_memory->mr, OBJECT(ms), "device-memory",
                        size);
+    address_space_init(&ms->device_memory->as, &ms->device_memory->mr,
+                       "device-memory");
     memory_region_add_subregion(get_system_memory(), ms->device_memory->base,
                                 &ms->device_memory->mr);
+
+    /* Track the number of memslots used by memory devices. */
+    ms->device_memory->listener.region_add = memory_devices_region_add;
+    ms->device_memory->listener.region_del = memory_devices_region_del;
+    memory_listener_register(&ms->device_memory->listener,
+                             &ms->device_memory->as);
 }
 
 static const TypeInfo memory_device_info = {