1 files changed, 46 insertions, 0 deletions

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index ec39741c87..d103b8c0ab 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1857,6 +1857,45 @@ static void pc_machine_set_pit(Object *obj, bool value, Error **errp)
     pcms->pit_enabled = value;
 }
 
+static void pc_machine_get_max_ram_below_4g(Object *obj, Visitor *v,
+                                            const char *name, void *opaque,
+                                            Error **errp)
+{
+    PCMachineState *pcms = PC_MACHINE(obj);
+    uint64_t value = pcms->max_ram_below_4g;
+
+    visit_type_size(v, name, &value, errp);
+}
+
+static void pc_machine_set_max_ram_below_4g(Object *obj, Visitor *v,
+                                            const char *name, void *opaque,
+                                            Error **errp)
+{
+    PCMachineState *pcms = PC_MACHINE(obj);
+    Error *error = NULL;
+    uint64_t value;
+
+    visit_type_size(v, name, &value, &error);
+    if (error) {
+        error_propagate(errp, error);
+        return;
+    }
+    if (value > 4 * GiB) {
+        error_setg(&error,
+                   "Machine option 'max-ram-below-4g=%"PRIu64
+                   "' expects size less than or equal to 4G", value);
+        error_propagate(errp, error);
+        return;
+    }
+
+    if (value < 1 * MiB) {
+        warn_report("Only %" PRIu64 " bytes of RAM below the 4GiB boundary,"
+                    "BIOS may not work with less than 1MiB", value);
+    }
+
+    pcms->max_ram_below_4g = value;
+}
+
 static void pc_machine_initfn(Object *obj)
 {
     PCMachineState *pcms = PC_MACHINE(obj);
@@ -1866,6 +1905,7 @@ static void pc_machine_initfn(Object *obj)
 #else
     pcms->vmport = ON_OFF_AUTO_OFF;
 #endif /* CONFIG_VMPORT */
+    pcms->max_ram_below_4g = 0; /* use default */
     /* acpi build is enabled by default if machine supports it */
     pcms->acpi_build_enabled = PC_MACHINE_GET_CLASS(pcms)->has_acpi_build;
     pcms->smbus_enabled = true;
@@ -1964,6 +2004,12 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
     mc->numa_mem_supported = true;
     mc->default_ram_id = "pc.ram";
 
+    object_class_property_add(oc, PC_MACHINE_MAX_RAM_BELOW_4G, "size",
+        pc_machine_get_max_ram_below_4g, pc_machine_set_max_ram_below_4g,
+        NULL, NULL);
+    object_class_property_set_description(oc, PC_MACHINE_MAX_RAM_BELOW_4G,
+        "Maximum ram below the 4G boundary (32bit boundary)");
+
     object_class_property_add(oc, PC_MACHINE_DEVMEM_REGION_SIZE, "int",
         pc_machine_get_device_memory_region_size, NULL,
         NULL, NULL);