diff --git a/src/mm/validate.rs b/src/mm/validate.rs
index 4cc37f93d..bc3be9116 100644
--- a/src/mm/validate.rs
+++ b/src/mm/validate.rs
@@ -128,20 +128,19 @@ impl ValidBitmap {
     }
 
     #[inline(always)]
-    fn index(&self, paddr: PhysAddr) -> (isize, usize) {
+    fn index(&self, paddr: PhysAddr) -> (usize, usize) {
         let page_offset = (paddr - self.pbase) / PAGE_SIZE;
-        let index: isize = (page_offset / 64).try_into().unwrap();
-        let bit: usize = page_offset % 64;
+        let index = page_offset / 64;
+        let bit = page_offset % 64;
 
         (index, bit)
     }
 
     fn clear_all(&mut self) {
-        let (mut i, bit) = self.index(self.pend);
+        let (mut index, bit) = self.index(self.pend);
         if bit != 0 {
-            i += 1;
+            index += 1;
         }
-        let index: usize = i.try_into().unwrap();
 
         unsafe {
             ptr::write_bytes(self.bitmap, 0, index);
@@ -159,7 +158,7 @@ impl ValidBitmap {
         }
 
         unsafe {
-            ptr::copy_nonoverlapping(self.bitmap, new_bitmap, count as usize);
+            ptr::copy_nonoverlapping(self.bitmap, new_bitmap, count);
         }
         self.bitmap = new_bitmap;
     }
@@ -179,9 +178,9 @@ impl ValidBitmap {
         assert!(self.check_addr(paddr));
 
         unsafe {
-            let mut val: u64 = ptr::read(self.bitmap.offset(index));
+            let mut val: u64 = ptr::read(self.bitmap.add(index));
             val |= 1u64 << bit;
-            ptr::write(self.bitmap.offset(index), val);
+            ptr::write(self.bitmap.add(index), val);
         }
     }
 
@@ -196,9 +195,9 @@ impl ValidBitmap {
         assert!(self.check_addr(paddr));
 
         unsafe {
-            let mut val: u64 = ptr::read(self.bitmap.offset(index));
+            let mut val: u64 = ptr::read(self.bitmap.add(index));
             val &= !(1u64 << bit);
-            ptr::write(self.bitmap.offset(index), val);
+            ptr::write(self.bitmap.add(index), val);
         }
     }
 
@@ -207,7 +206,7 @@ impl ValidBitmap {
             return;
         }
 
-        const NR_INDEX: isize = (PAGE_SIZE_2M / (PAGE_SIZE * 64)) as isize;
+        const NR_INDEX: usize = PAGE_SIZE_2M / (PAGE_SIZE * 64);
         let (index, _) = self.index(paddr);
 
         assert!(paddr.is_aligned(PAGE_SIZE_2M));
@@ -215,7 +214,7 @@ impl ValidBitmap {
 
         for i in 0..NR_INDEX {
             unsafe {
-                ptr::write(self.bitmap.offset(index + i), val);
+                ptr::write(self.bitmap.add(index + i), val);
             }
         }
     }
@@ -228,10 +227,10 @@ impl ValidBitmap {
         self.set_2m(paddr, 0u64);
     }
 
-    fn modify_bitmap_word(&mut self, index: isize, mask: u64, new_val: u64) {
-        let val = unsafe { ptr::read(self.bitmap.offset(index)) };
+    fn modify_bitmap_word(&mut self, index: usize, mask: u64, new_val: u64) {
+        let val = unsafe { ptr::read(self.bitmap.add(index)) };
         let val = (val & !mask) | (new_val & mask);
-        unsafe { ptr::write(self.bitmap.offset(index), val) };
+        unsafe { ptr::write(self.bitmap.add(index), val) };
     }
 
     fn set_range(&mut self, paddr_begin: PhysAddr, paddr_end: PhysAddr, new_val: bool) {
@@ -251,7 +250,7 @@ impl ValidBitmap {
             self.modify_bitmap_word(index_head, mask_head, new_val);
 
             for index in (index_head + 1)..index_tail {
-                unsafe { ptr::write(self.bitmap.offset(index), new_val) };
+                unsafe { ptr::write(self.bitmap.add(index), new_val) };
             }
 
             if bit_tail_end != 0 {
@@ -284,7 +283,7 @@ impl ValidBitmap {
 
         unsafe {
             let mask: u64 = 1u64 << bit;
-            let val: u64 = ptr::read(self.bitmap.offset(index));
+            let val: u64 = ptr::read(self.bitmap.add(index));
 
             (val & mask) == mask
         }