diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 892bae4f3a..9596c7c7f1 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -29,6 +29,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/units.h"
 #include "qapi/error.h"
 #include "hw/sysbus.h"
 #include "hw/arm/arm.h"
@@ -121,7 +122,7 @@
  * Note that devices should generally be placed at multiples of 0x10000,
  * to accommodate guests using 64K pages.
  */
-static const MemMapEntry a15memmap[] = {
+static const MemMapEntry base_memmap[] = {
     /* Space up to 0x8000000 is reserved for a boot ROM */
     [VIRT_FLASH] =              {          0, 0x08000000 },
     [VIRT_CPUPERIPHS] =         { 0x08000000, 0x00020000 },
@@ -149,11 +150,24 @@ static const MemMapEntry a15memmap[] = {
     [VIRT_PCIE_PIO] =           { 0x3eff0000, 0x00010000 },
     [VIRT_PCIE_ECAM] =          { 0x3f000000, 0x01000000 },
     [VIRT_MEM] =                { 0x40000000, RAMLIMIT_BYTES },
+};
+
+/*
+ * Highmem IO Regions: This memory map is floating, located after the RAM.
+ * Each MemMapEntry base (GPA) will be dynamically computed, depending on the
+ * top of the RAM, so that its base get the same alignment as the size,
+ * ie. a 512GiB entry will be aligned on a 512GiB boundary. If there is
+ * less than 256GiB of RAM, the floating area starts at the 256GiB mark.
+ * 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).
+ */
+static MemMapEntry extended_memmap[] = {
     /* Additional 64 MB redist region (can contain up to 512 redistributors) */
-    [VIRT_HIGH_GIC_REDIST2] =   { 0x4000000000ULL, 0x4000000 },
-    [VIRT_HIGH_PCIE_ECAM] =     { 0x4010000000ULL, 0x10000000 },
-    /* Second PCIe window, 512GB wide at the 512GB boundary */
-    [VIRT_HIGH_PCIE_MMIO] =     { 0x8000000000ULL, 0x8000000000ULL },
+    [VIRT_HIGH_GIC_REDIST2] =   { 0x0, 64 * MiB },
+    [VIRT_HIGH_PCIE_ECAM] =     { 0x0, 256 * MiB },
+    /* Second PCIe window */
+    [VIRT_HIGH_PCIE_MMIO] =     { 0x0, 512 * GiB },
 };
 
 static const int a15irqmap[] = {
@@ -1354,6 +1368,29 @@ static uint64_t virt_cpu_mp_affinity(VirtMachineState *vms, int idx)
     return arm_cpu_mp_affinity(idx, clustersz);
 }
 
+static void virt_set_memmap(VirtMachineState *vms)
+{
+    hwaddr base;
+    int i;
+
+    vms->memmap = extended_memmap;
+
+    for (i = 0; i < ARRAY_SIZE(base_memmap); i++) {
+        vms->memmap[i] = base_memmap[i];
+    }
+
+    base = 256 * GiB; /* Top of the legacy initial RAM region */
+
+    for (i = VIRT_LOWMEMMAP_LAST; i < ARRAY_SIZE(extended_memmap); i++) {
+        hwaddr size = extended_memmap[i].size;
+
+        base = ROUND_UP(base, size);
+        vms->memmap[i].base = base;
+        vms->memmap[i].size = size;
+        base += size;
+    }
+}
+
 static void machvirt_init(MachineState *machine)
 {
     VirtMachineState *vms = VIRT_MACHINE(machine);
@@ -1368,6 +1405,8 @@ static void machvirt_init(MachineState *machine)
     bool firmware_loaded = bios_name || drive_get(IF_PFLASH, 0, 0);
     bool aarch64 = true;
 
+    virt_set_memmap(vms);
+
     /* We can probe only here because during property set
      * KVM is not available yet
      */
@@ -1845,7 +1884,6 @@ static void virt_instance_init(Object *obj)
                                     "Valid values are none and smmuv3",
                                     NULL);
 
-    vms->memmap = a15memmap;
     vms->irqmap = a15irqmap;
 }
 
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index a27086d524..f3f7fae4ac 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -64,7 +64,6 @@ enum {
     VIRT_GIC_VCPU,
     VIRT_GIC_ITS,
     VIRT_GIC_REDIST,
-    VIRT_HIGH_GIC_REDIST2,
     VIRT_SMMU,
     VIRT_UART,
     VIRT_MMIO,
@@ -74,12 +73,18 @@ enum {
     VIRT_PCIE_MMIO,
     VIRT_PCIE_PIO,
     VIRT_PCIE_ECAM,
-    VIRT_HIGH_PCIE_ECAM,
     VIRT_PLATFORM_BUS,
-    VIRT_HIGH_PCIE_MMIO,
     VIRT_GPIO,
     VIRT_SECURE_UART,
     VIRT_SECURE_MEM,
+    VIRT_LOWMEMMAP_LAST,
+};
+
+/* indices of IO regions located after the RAM */
+enum {
+    VIRT_HIGH_GIC_REDIST2 =  VIRT_LOWMEMMAP_LAST,
+    VIRT_HIGH_PCIE_ECAM,
+    VIRT_HIGH_PCIE_MMIO,
 };
 
 typedef enum VirtIOMMUType {
@@ -116,7 +121,7 @@ typedef struct {
     int32_t gic_version;
     VirtIOMMUType iommu;
     struct arm_boot_info bootinfo;
-    const MemMapEntry *memmap;
+    MemMapEntry *memmap;
     const int *irqmap;
     int smp_cpus;
     void *fdt;