diff --git a/src/arch/riscv32/boot/entry.asm b/src/arch/riscv32/boot/entry.asm
index 0a6898d..6c11050 100644
--- a/src/arch/riscv32/boot/entry.asm
+++ b/src/arch/riscv32/boot/entry.asm
@@ -8,6 +8,6 @@ kern_entry:
     .align 12  #PGSHIFT
     .global bootstack
 bootstack:
-    .space 4096 * 8  #KSTACKSIZE
+    .space 4096 * 16  #KSTACKSIZE
     .global bootstacktop
 bootstacktop:
diff --git a/src/arch/riscv32/memory.rs b/src/arch/riscv32/memory.rs
index 3f8b146..a3aaacc 100644
--- a/src/arch/riscv32/memory.rs
+++ b/src/arch/riscv32/memory.rs
@@ -11,8 +11,10 @@ pub fn init() {
     let frame = Frame::of_addr(PhysAddr::new(&PAGE_TABLE_ROOT as *const _ as u32));
     super::paging::setup_page_table(frame);
     init_frame_allocator();
-    remap_the_kernel();
+    let ms = remap_the_kernel();
     init_heap();
+    use core::mem::forget;
+    forget(ms);
 }
 
 fn init_frame_allocator() {
@@ -32,7 +34,7 @@ fn init_frame_allocator() {
     }
 }
 
-fn remap_the_kernel() {
+fn remap_the_kernel() -> MemorySet {
     use consts::{KERNEL_HEAP_OFFSET, KERNEL_HEAP_SIZE};
     let kstack = Stack {
         top: bootstacktop as usize,
@@ -47,6 +49,7 @@ fn remap_the_kernel() {
     ms.push(MemoryArea::new(KERNEL_HEAP_OFFSET, KERNEL_HEAP_OFFSET + KERNEL_HEAP_SIZE, MemoryAttr::default(), "kernel_heap"));
     unsafe { ms.activate(); }
     info!("kernel remap end");
+    ms
 }
 
 // Symbols provided by linker script
diff --git a/src/arch/riscv32/mod.rs b/src/arch/riscv32/mod.rs
index 02fd440..96f804a 100644
--- a/src/arch/riscv32/mod.rs
+++ b/src/arch/riscv32/mod.rs
@@ -11,6 +11,5 @@ pub fn init() {
     println!("Hello RISCV! {}", 123);
     interrupt::init();
     memory::init();
-//    timer::init();
-    loop {}
+    timer::init();
 }
\ No newline at end of file
diff --git a/src/arch/riscv32/paging.rs b/src/arch/riscv32/paging.rs
index a1aff40..ffea89b 100644
--- a/src/arch/riscv32/paging.rs
+++ b/src/arch/riscv32/paging.rs
@@ -69,11 +69,12 @@ impl PageTable for ActivePageTable {
     }
 }
 
+const ROOT_PAGE_TABLE: *mut RvPageTable =
+    (((RECURSIVE_PAGE_PML4 << 10) | (RECURSIVE_PAGE_PML4 + 1)) << 12) as *mut RvPageTable;
+
 impl ActivePageTable {
     pub unsafe fn new() -> Self {
-        let root_addr = ((RECURSIVE_PAGE_PML4 << 10) | (RECURSIVE_PAGE_PML4 + 1)) << 12;
-        println!("{:x?}", &*(root_addr as *const RvPageTable));
-        ActivePageTable(RecursivePageTable::new(&mut *(root_addr as *mut _)).unwrap())
+        ActivePageTable(RecursivePageTable::new(&mut *ROOT_PAGE_TABLE).unwrap())
     }
     fn with_temporary_map(&mut self, frame: &Frame, f: impl FnOnce(&mut ActivePageTable, &mut RvPageTable)) {
         // Create a temporary page
@@ -177,6 +178,7 @@ impl InactivePageTable for InactivePageTable0 {
         debug!("switch table {:?} -> {:?}", old_frame, new_frame);
         if old_frame != new_frame {
             satp::set(satp::Mode::Sv32, 0, new_frame);
+            sfence_vma_all();
         }
     }
 
@@ -186,11 +188,13 @@ impl InactivePageTable for InactivePageTable0 {
         debug!("switch table {:?} -> {:?}", old_frame, new_frame);
         if old_frame != new_frame {
             satp::set(satp::Mode::Sv32, 0, new_frame);
+            sfence_vma_all();
         }
         f();
         debug!("switch table {:?} -> {:?}", new_frame, old_frame);
         if old_frame != new_frame {
             satp::set(satp::Mode::Sv32, 0, old_frame);
+            sfence_vma_all();
         }
     }
 
@@ -209,7 +213,7 @@ impl InactivePageTable for InactivePageTable0 {
 
 impl InactivePageTable0 {
     fn map_kernel(&mut self) {
-        let mut table = unsafe { &mut *(0xfffff000 as *mut RvPageTable) };
+        let table = unsafe { &mut *ROOT_PAGE_TABLE };
         let e1 = table[KERNEL_PML4].clone();
         let e2 = table[KERNEL_PML4 + 1].clone();
         self.edit(|_| {
diff --git a/src/lib.rs b/src/lib.rs
index d561b6b..7f72192 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -95,7 +95,7 @@ mod arch;
 #[cfg(target_arch = "riscv")]
 pub extern fn rust_main() -> ! {
     arch::init();
-    memory::init_heap();
+    println!("RISCV init end");
     loop {}
 }