diff --git a/include/xen/interface/platform.h b/include/xen/interface/platform.h
index 5e36932..2c4fb4b 100644
--- a/include/xen/interface/platform.h
+++ b/include/xen/interface/platform.h
@@ -324,10 +324,14 @@
 };
 DEFINE_GUEST_HANDLE_STRUCT(xenpf_cpu_ol);
 
-/*
- * CMD 58 and 59 are reserved for cpu hotadd and memory hotadd,
- * which are already occupied at Xen hypervisor side.
- */
+#define XENPF_mem_hotadd	59
+struct xenpf_mem_hotadd {
+	uint64_t spfn;
+	uint64_t epfn;
+	uint32_t pxm;
+	uint32_t flags;
+};
+
 #define XENPF_core_parking     60
 struct xenpf_core_parking {
 	/* IN variables */
@@ -357,6 +361,7 @@
 		struct xenpf_set_processor_pminfo set_pminfo;
 		struct xenpf_pcpuinfo          pcpu_info;
 		struct xenpf_cpu_ol            cpu_ol;
+		struct xenpf_mem_hotadd        mem_add;
 		struct xenpf_core_parking      core_parking;
 		uint8_t                        pad[128];
 	} u;