diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 1987640..86c90df 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -102,6 +102,7 @@ struct sPAPRMachineClass {
 
     /*< public >*/
     bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
+    bool update_dt_enabled;    /* enable KVMPPC_H_UPDATE_DT */
     bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
     bool pre_2_10_has_unused_icps;
     bool legacy_irq_allocation;
@@ -138,6 +139,9 @@ struct sPAPRMachineState {
     int vrma_adjust;
     ssize_t rtas_size;
     void *rtas_blob;
+    uint32_t fdt_size;
+    uint32_t fdt_initial_size;
+    void *fdt_blob;
     long kernel_size;
     bool kernel_le;
     uint32_t initrd_base;
@@ -464,7 +468,8 @@ struct sPAPRMachineState {
 #define KVMPPC_H_LOGICAL_MEMOP  (KVMPPC_HCALL_BASE + 0x1)
 /* Client Architecture support */
 #define KVMPPC_H_CAS            (KVMPPC_HCALL_BASE + 0x2)
-#define KVMPPC_HCALL_MAX        KVMPPC_H_CAS
+#define KVMPPC_H_UPDATE_DT      (KVMPPC_HCALL_BASE + 0x3)
+#define KVMPPC_HCALL_MAX        KVMPPC_H_UPDATE_DT
 
 typedef struct sPAPRDeviceTreeUpdateHeader {
     uint32_t version_id;
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 8a18250..984bf32 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1654,7 +1654,10 @@ static void spapr_machine_reset(void)
     /* Load the fdt */
     qemu_fdt_dumpdtb(fdt, fdt_totalsize(fdt));
     cpu_physical_memory_write(fdt_addr, fdt, fdt_totalsize(fdt));
-    g_free(fdt);
+    g_free(spapr->fdt_blob);
+    spapr->fdt_size = fdt_totalsize(fdt);
+    spapr->fdt_initial_size = spapr->fdt_size;
+    spapr->fdt_blob = fdt;
 
     /* Set up the entry state */
     spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT, fdt_addr);
@@ -1908,6 +1911,27 @@ static const VMStateDescription vmstate_spapr_irq_map = {
     },
 };
 
+static bool spapr_dtb_needed(void *opaque)
+{
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(opaque);
+
+    return smc->update_dt_enabled;
+}
+
+static const VMStateDescription vmstate_spapr_dtb = {
+    .name = "spapr_dtb",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = spapr_dtb_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(fdt_initial_size, sPAPRMachineState),
+        VMSTATE_UINT32(fdt_size, sPAPRMachineState),
+        VMSTATE_VBUFFER_ALLOC_UINT32(fdt_blob, sPAPRMachineState, 0, NULL,
+                                     fdt_size),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
 static const VMStateDescription vmstate_spapr = {
     .name = "spapr",
     .version_id = 3,
@@ -1937,6 +1961,7 @@ static const VMStateDescription vmstate_spapr = {
         &vmstate_spapr_cap_ibs,
         &vmstate_spapr_irq_map,
         &vmstate_spapr_cap_nested_kvm_hv,
+        &vmstate_spapr_dtb,
         NULL
     }
 };
@@ -3871,6 +3896,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     hc->unplug = spapr_machine_device_unplug;
 
     smc->dr_lmb_enabled = true;
+    smc->update_dt_enabled = true;
     mc->default_cpu_type = POWERPC_CPU_TYPE_NAME("power8_v2.0");
     mc->has_hotpluggable_cpus = true;
     smc->resize_hpt_default = SPAPR_RESIZE_HPT_ENABLED;
@@ -3981,8 +4007,11 @@ static void spapr_machine_3_1_instance_options(MachineState *machine)
 
 static void spapr_machine_3_1_class_options(MachineClass *mc)
 {
+    sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
+
     spapr_machine_4_0_class_options(mc);
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_3_1);
+    smc->update_dt_enabled = false;
 }
 
 DEFINE_SPAPR_MACHINE(3_1, "3.1", false);
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index ae913d0..dfd3cf3 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -1717,6 +1717,46 @@ static target_ulong h_get_cpu_characteristics(PowerPCCPU *cpu,
 
     args[0] = characteristics;
     args[1] = behaviour;
+    return H_SUCCESS;
+}
+
+static target_ulong h_update_dt(PowerPCCPU *cpu, sPAPRMachineState *spapr,
+                                target_ulong opcode, target_ulong *args)
+{
+    target_ulong dt = ppc64_phys_to_real(args[0]);
+    struct fdt_header hdr = { 0 };
+    unsigned cb;
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
+    void *fdt;
+
+    cpu_physical_memory_read(dt, &hdr, sizeof(hdr));
+    cb = fdt32_to_cpu(hdr.totalsize);
+
+    if (!smc->update_dt_enabled) {
+        return H_SUCCESS;
+    }
+
+    /* Check that the fdt did not grow out of proportion */
+    if (cb > spapr->fdt_initial_size * 2) {
+        trace_spapr_update_dt_failed_size(spapr->fdt_initial_size, cb,
+            fdt32_to_cpu(hdr.magic));
+        return H_PARAMETER;
+    }
+
+    fdt = g_malloc0(cb);
+    cpu_physical_memory_read(dt, fdt, cb);
+
+    /* Check the fdt consostency */
+    if (fdt_check_full(fdt, cb)) {
+        trace_spapr_update_dt_failed_check(spapr->fdt_initial_size, cb,
+            fdt32_to_cpu(hdr.magic));
+        return H_PARAMETER;
+    }
+
+    g_free(spapr->fdt_blob);
+    spapr->fdt_size = cb;
+    spapr->fdt_blob = fdt;
+    trace_spapr_update_dt(cb);
 
     return H_SUCCESS;
 }
@@ -1822,6 +1862,8 @@ static void hypercall_register_types(void)
 
     /* ibm,client-architecture-support support */
     spapr_register_hypercall(KVMPPC_H_CAS, h_client_architecture_support);
+
+    spapr_register_hypercall(KVMPPC_H_UPDATE_DT, h_update_dt);
 }
 
 type_init(hypercall_register_types)
diff --git a/hw/ppc/trace-events b/hw/ppc/trace-events
index dc5e65a..0af155e 100644
--- a/hw/ppc/trace-events
+++ b/hw/ppc/trace-events
@@ -22,6 +22,9 @@ spapr_cas_pvr_try(uint32_t pvr) "0x%x"
 spapr_cas_pvr(uint32_t cur_pvr, bool explicit_match, uint32_t new_pvr) "current=0x%x, explicit_match=%u, new=0x%x"
 spapr_h_resize_hpt_prepare(uint64_t flags, uint64_t shift) "flags=0x%"PRIx64", shift=%"PRIu64
 spapr_h_resize_hpt_commit(uint64_t flags, uint64_t shift) "flags=0x%"PRIx64", shift=%"PRIu64
+spapr_update_dt(unsigned cb) "New blob %u bytes"
+spapr_update_dt_failed_size(unsigned cbold, unsigned cbnew, unsigned magic) "Old blob %u bytes, new blob %u bytes, magic 0x%x"
+spapr_update_dt_failed_check(unsigned cbold, unsigned cbnew, unsigned magic) "Old blob %u bytes, new blob %u bytes, magic 0x%x"
 
 # hw/ppc/spapr_iommu.c
 spapr_iommu_put(uint64_t liobn, uint64_t ioba, uint64_t tce, uint64_t ret) "liobn=0x%"PRIx64" ioba=0x%"PRIx64" tce=0x%"PRIx64" ret=%"PRId64
