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-rw-r--r--docs/system/arm/virt.rst4
-rw-r--r--hw/arm/virt.c32
-rw-r--r--include/hw/arm/virt.h1
3 files changed, 37 insertions, 0 deletions
diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst
index 20442ea2c1..4454706392 100644
--- a/docs/system/arm/virt.rst
+++ b/docs/system/arm/virt.rst
@@ -94,6 +94,10 @@ highmem
   address space above 32 bits. The default is ``on`` for machine types
   later than ``virt-2.12``.
 
+compact-highmem
+  Set ``on``/``off`` to enable/disable the compact layout for high memory regions.
+  The default is ``on`` for machine types later than ``virt-7.2``.
+
 gic-version
   Specify the version of the Generic Interrupt Controller (GIC) to provide.
   Valid values are:
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 807175707e..3d1371c05c 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -174,6 +174,12 @@ static const MemMapEntry base_memmap[] = {
  * Note the extended_memmap is sized so that it eventually also includes the
  * base_memmap entries (VIRT_HIGH_GIC_REDIST2 index is greater than the last
  * index of base_memmap).
+ *
+ * The memory map for these Highmem IO Regions can be in legacy or compact
+ * layout, depending on 'compact-highmem' property. With legacy layout, the
+ * PA space for one specific region is always reserved, even if the region
+ * has been disabled or doesn't fit into the PA space. However, the PA space
+ * for the region won't be reserved in these circumstances with compact layout.
  */
 static MemMapEntry extended_memmap[] = {
     /* Additional 64 MB redist region (can contain up to 512 redistributors) */
@@ -2352,6 +2358,20 @@ static void virt_set_highmem(Object *obj, bool value, Error **errp)
     vms->highmem = value;
 }
 
+static bool virt_get_compact_highmem(Object *obj, Error **errp)
+{
+    VirtMachineState *vms = VIRT_MACHINE(obj);
+
+    return vms->highmem_compact;
+}
+
+static void virt_set_compact_highmem(Object *obj, bool value, Error **errp)
+{
+    VirtMachineState *vms = VIRT_MACHINE(obj);
+
+    vms->highmem_compact = value;
+}
+
 static bool virt_get_its(Object *obj, Error **errp)
 {
     VirtMachineState *vms = VIRT_MACHINE(obj);
@@ -2970,6 +2990,13 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
                                           "Set on/off to enable/disable using "
                                           "physical address space above 32 bits");
 
+    object_class_property_add_bool(oc, "compact-highmem",
+                                   virt_get_compact_highmem,
+                                   virt_set_compact_highmem);
+    object_class_property_set_description(oc, "compact-highmem",
+                                          "Set on/off to enable/disable compact "
+                                          "layout for high memory regions");
+
     object_class_property_add_str(oc, "gic-version", virt_get_gic_version,
                                   virt_set_gic_version);
     object_class_property_set_description(oc, "gic-version",
@@ -3054,6 +3081,7 @@ static void virt_instance_init(Object *obj)
 
     /* High memory is enabled by default */
     vms->highmem = true;
+    vms->highmem_compact = !vmc->no_highmem_compact;
     vms->gic_version = VIRT_GIC_VERSION_NOSEL;
 
     vms->highmem_ecam = !vmc->no_highmem_ecam;
@@ -3123,8 +3151,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(7, 2)
 
 static void virt_machine_7_1_options(MachineClass *mc)
 {
+    VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
+
     virt_machine_7_2_options(mc);
     compat_props_add(mc->compat_props, hw_compat_7_1, hw_compat_7_1_len);
+    /* Compact layout for high memory regions was introduced with 7.2 */
+    vmc->no_highmem_compact = true;
 }
 DEFINE_VIRT_MACHINE(7, 1)
 
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 709f623741..c7dd59d7f1 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -125,6 +125,7 @@ struct VirtMachineClass {
     bool no_pmu;
     bool claim_edge_triggered_timers;
     bool smbios_old_sys_ver;
+    bool no_highmem_compact;
     bool no_highmem_ecam;
     bool no_ged;   /* Machines < 4.2 have no support for ACPI GED device */
     bool kvm_no_adjvtime;