diff --git a/hypervisor/bsp/uefi/efi/boot.c b/hypervisor/bsp/uefi/efi/boot.c
index 8e2eeb669..d2282f523 100644
--- a/hypervisor/bsp/uefi/efi/boot.c
+++ b/hypervisor/bsp/uefi/efi/boot.c
@@ -224,9 +224,11 @@ switch_to_guest_mode(EFI_HANDLE image)
 	efi_ctx = (struct boot_ctx *)(UINTN)addr;
 
 	/* reserve secondary memory region for hv */
-	err = emalloc_for_low_mem(&addr, CONFIG_LOW_RAM_SIZE);
+	err = emalloc_reserved_mem(&addr, CONFIG_LOW_RAM_SIZE, MEM_ADDR_1MB);
 	if (err != EFI_SUCCESS)
 		goto out;
+	if (addr < 4096)
+		Print(L"Warning: CPU trampoline code buf occupied zero-page\n");
 
 	efi_ctx->ap_trampoline_buf = (void *)addr;
 
diff --git a/hypervisor/bsp/uefi/efi/efilinux.h b/hypervisor/bsp/uefi/efi/efilinux.h
index 08fc49f90..70aad77e2 100644
--- a/hypervisor/bsp/uefi/efi/efilinux.h
+++ b/hypervisor/bsp/uefi/efi/efilinux.h
@@ -45,6 +45,8 @@
 #define EFILINUX_VERSION_MAJOR 1
 #define EFILINUX_VERSION_MINOR 0
 
+#define MEM_ADDR_1MB (1 << 20)
+
 
 extern EFI_SYSTEM_TABLE *sys_table;
 extern EFI_BOOT_SERVICES *boot;
@@ -184,6 +186,22 @@ handle_protocol(EFI_HANDLE handle, EFI_GUID *protocol, void **interface)
 }
 
 
+/*
+ * emalloc_reserved_mem - it is called to allocate memory hypervisor itself
+ * and trampoline code, and mark the allocate memory as EfiReserved memory
+ * type so that SOS won't touch it during boot.
+ * @addr: a pointer to the allocated address on success
+ * @size: size in bytes of the requested allocation
+ * @max_addr: the allocated memory must be no more than this threshold
+ */
+static inline EFI_STATUS emalloc_reserved_mem(EFI_PHYSICAL_ADDRESS *addr,
+	UINTN size, EFI_PHYSICAL_ADDRESS max_addr)
+{
+	*addr = max_addr;
+	return allocate_pages(AllocateMaxAddress, EfiReservedMemoryType,
+		EFI_SIZE_TO_PAGES(size), addr);
+}
+
 /**
  * exit - Terminate a loaded EFI image
  * @image: firmware-allocated handle that identifies the image
diff --git a/hypervisor/bsp/uefi/efi/malloc.c b/hypervisor/bsp/uefi/efi/malloc.c
index 7b0591fe4..087670ca5 100644
--- a/hypervisor/bsp/uefi/efi/malloc.c
+++ b/hypervisor/bsp/uefi/efi/malloc.c
@@ -164,65 +164,6 @@ fail:
 	return err;
 }
 
-EFI_STATUS emalloc_for_low_mem(EFI_PHYSICAL_ADDRESS *addr, UINTN size)
-{
-	UINTN map_size, map_key, desc_size;
-	EFI_MEMORY_DESCRIPTOR *map_buf;
-	UINTN d, map_end;
-	UINT32 desc_version;
-	EFI_STATUS err;
-	UINTN nr_pages = EFI_SIZE_TO_PAGES(size);
-
-	err = memory_map(&map_buf, &map_size, &map_key,
-			 &desc_size, &desc_version);
-
-	if (err != EFI_SUCCESS)
-		goto fail;
-
-	d = (UINTN)map_buf;
-	map_end = (UINTN)map_buf + map_size;
-
-	for (; d < map_end; d += desc_size) {
-		EFI_MEMORY_DESCRIPTOR *desc;
-		EFI_PHYSICAL_ADDRESS start, end, aligned;
-
-		desc = (EFI_MEMORY_DESCRIPTOR *)d;
-		if (desc->Type != EfiConventionalMemory)
-			continue;
-
-		if (desc->NumberOfPages < nr_pages)
-			continue;
-
-		start = desc->PhysicalStart;
-		end = start + (desc->NumberOfPages << EFI_PAGE_SHIFT);
-		size = nr_pages << EFI_PAGE_SHIFT;
-
-		/* allocate in low memory only */
-		if (start >= 1 << 20)
-			continue;
-
-		if (end > 1 << 20)
-			end = (1 << 20);
-
-		if (end - start >= size) {
-			aligned = end - size;
-			err = allocate_pages(AllocateAddress, EfiReservedMemoryType,
-						 nr_pages, &aligned);
-			if (err == EFI_SUCCESS) {
-				*addr = aligned;
-				break;
-			}
-		}
-	}
-
-	if (d == map_end)
-		err = EFI_OUT_OF_RESOURCES;
-
-	free_pool(map_buf);
-fail:
-	return err;
-}
-
 EFI_STATUS __emalloc(UINTN size, UINTN min_addr, EFI_PHYSICAL_ADDRESS *addr,
 	EFI_MEMORY_TYPE mem_type)
 {
diff --git a/hypervisor/bsp/uefi/efi/stdlib.h b/hypervisor/bsp/uefi/efi/stdlib.h
index 5e1c20df1..8fbbff980 100644
--- a/hypervisor/bsp/uefi/efi/stdlib.h
+++ b/hypervisor/bsp/uefi/efi/stdlib.h
@@ -50,7 +50,6 @@ extern void *calloc(UINTN nmemb, UINTN size);
 
 extern EFI_STATUS emalloc(UINTN, UINTN, EFI_PHYSICAL_ADDRESS *);
 extern EFI_STATUS __emalloc(UINTN, UINTN, EFI_PHYSICAL_ADDRESS *, EFI_MEMORY_TYPE);
-extern EFI_STATUS emalloc_for_low_mem(EFI_PHYSICAL_ADDRESS *addr, UINTN size);
 extern void efree(EFI_PHYSICAL_ADDRESS, UINTN);
 
 static inline void memset(void *dstv, char ch, UINTN size)