From 2041a7c0d4edc1d73aa0ce31fb4d7af7a5cd3503 Mon Sep 17 00:00:00 2001
From: Yifan Wu <shinbokuow@163.com>
Date: Sat, 13 Nov 2021 03:06:44 -0800
Subject: [PATCH] Now construction of PA/VA only uses 56/39 bits.

---
 os/src/mm/address.rs | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/os/src/mm/address.rs b/os/src/mm/address.rs
index d5828ed2..107f35c6 100644
--- a/os/src/mm/address.rs
+++ b/os/src/mm/address.rs
@@ -2,6 +2,11 @@ use crate::config::{PAGE_SIZE, PAGE_SIZE_BITS};
 use super::PageTableEntry;
 use core::fmt::{self, Debug, Formatter};
 
+const PA_WIDTH_SV39: usize = 56;
+const VA_WIDTH_SV39: usize = 39;
+const PPN_WIDTH_SV39: usize = PA_WIDTH_SV39 - PAGE_SIZE_BITS;
+const VPN_WIDTH_SV39: usize = VA_WIDTH_SV39 - PAGE_SIZE_BITS;
+
 /// Definitions
 #[repr(C)]
 #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
@@ -47,16 +52,16 @@ impl Debug for PhysPageNum {
 /// usize -> T: usize.into()
 
 impl From<usize> for PhysAddr {
-    fn from(v: usize) -> Self { Self(v) }
+    fn from(v: usize) -> Self { Self(v & ( (1 << PA_WIDTH_SV39) - 1 )) }
 }
 impl From<usize> for PhysPageNum {
-    fn from(v: usize) -> Self { Self(v) }
+    fn from(v: usize) -> Self { Self(v & ( (1 << PPN_WIDTH_SV39) - 1 )) }
 }
 impl From<usize> for VirtAddr {
-    fn from(v: usize) -> Self { Self(v) }
+    fn from(v: usize) -> Self { Self(v & ( (1 << VA_WIDTH_SV39) - 1 )) }
 }
 impl From<usize> for VirtPageNum {
-    fn from(v: usize) -> Self { Self(v) }
+    fn from(v: usize) -> Self { Self(v & ( (1 << VPN_WIDTH_SV39) - 1 )) }
 }
 impl From<PhysAddr> for usize {
     fn from(v: PhysAddr) -> Self { v.0 }
@@ -206,4 +211,4 @@ impl<T> Iterator for SimpleRangeIterator<T> where
         }
     }
 }
-pub type VPNRange = SimpleRange<VirtPageNum>;
\ No newline at end of file
+pub type VPNRange = SimpleRange<VirtPageNum>;