diff --git a/pk/entry.S b/pk/entry.S
index 5fe0be2..6f0d1a0 100644
--- a/pk/entry.S
+++ b/pk/entry.S
@@ -128,8 +128,15 @@ pop_tf:  # write the trap frame onto the stack
 trap_entry:
   mtpcr $ra,ASM_CR(PCR_K0)
   mtpcr $x2,ASM_CR(PCR_K1)
+
+  # when coming from kernel, continue below its stack
+  mfpcr $ra,ASM_CR(PCR_SR)
+  and   $ra,$ra,SR_PS
+  add   $x2, $sp, -320
+  bnez  $ra, 1f
   la    $x2,stack_top-320
-  jal   save_tf
+
+1:jal   save_tf
   move  $sp,$x2
   move  $a0,$x2
   jal    handle_trap
diff --git a/pk/handlers.c b/pk/handlers.c
index 597c675..c9b6a96 100644
--- a/pk/handlers.c
+++ b/pk/handlers.c
@@ -101,10 +101,13 @@ static void handle_interrupt(trapframe_t* tf)
 
   for(int i = 0; interrupts; interrupts >>= 1, i++)
   {
-    if(i == TIMER_IRQ)
-      handle_timer_interrupt(tf);
-    else
-      handle_bad_interrupt(tf,i);
+    if(interrupts & 1)
+    {
+      if(i == TIMER_IRQ)
+        handle_timer_interrupt(tf);
+      else
+        handle_bad_interrupt(tf,i);
+    }
   }
 }
 
diff --git a/pk/pcr.h b/pk/pcr.h
index 8f182dc..e9643ae 100644
--- a/pk/pcr.h
+++ b/pk/pcr.h
@@ -32,7 +32,7 @@
 
 #define MEMSIZE_SHIFT 12
 
-#define TIMER_PERIOD 0x1000000
+#define TIMER_PERIOD 0x1000
 #define TIMER_IRQ 7
 
 #define CAUSE_EXCCODE 0x000000FF
diff --git a/pk/riscv-pk.S b/pk/riscv-pk.S
index 0696a2d..6b91787 100644
--- a/pk/riscv-pk.S
+++ b/pk/riscv-pk.S
@@ -14,9 +14,10 @@ __start:
   mtpcr $t0, ASM_CR(PCR_EVEC)
 
   mtpcr $x0, ASM_CR(PCR_COUNT)
-  mtpcr $x0, ASM_CR(PCR_COMPARE)
+  li    $t0, TIMER_PERIOD
+  mtpcr $t0, ASM_CR(PCR_COMPARE)
 
-  li $t0, SR_S | SR_PS | SR_ET | SR_IM | SR_EC | SR_SX
+  li $t0, SR_S | SR_PS | SR_ET | SR_EC | SR_SX
   or $t1, $t0, SR_EF | SR_EV
   mtpcr $t1, ASM_CR(PCR_SR)
   mfpcr $t1, ASM_CR(PCR_SR)