Add `MemoryRegionType::is_physical`

ostd/src/boot/memory_region.rs

@@ -32,6 +32,21 @@ pub enum MemoryRegionType {
     Usable = 8,
 }
 
+impl MemoryRegionType {
+    /// Returns whether the memory region corresponds to physical memory.
+    ///
+    /// The linear mapping will cover memory addresses up to the top of the physical memory.
+    /// Therefore, if this method returns `false`, the memory region may not be included in the
+    /// linear mapping.
+    pub fn is_physical(self) -> bool {
+        // Bad memory or I/O memory is not physical. All other memory should be physical.
+        !matches!(
+            self,
+            Self::BadMemory | Self::Unknown | Self::Reserved | Self::Framebuffer
+        )
+    }
+}
+
 /// The information of initial memory regions that are needed by the kernel.
 /// The sections are **not** guaranteed to not overlap. The region must be page aligned.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]

ostd/src/mm/frame/meta.rs

@@ -458,12 +458,7 @@ pub(crate) unsafe fn init() -> Segment<MetaPageMeta> {
         let regions = &crate::boot::EARLY_INFO.get().unwrap().memory_regions;
         regions
             .iter()
-            .filter(|r| {
-                matches!(
-                    r.typ(),
-                    MemoryRegionType::Usable | MemoryRegionType::Reclaimable
-                )
-            })
+            .filter(|r| r.typ().is_physical())
             .map(|r| r.base() + r.len())
             .max()
             .unwrap()
@@ -592,11 +587,7 @@ macro_rules! mark_ranges {
 fn mark_unusable_ranges() {
     let regions = &crate::boot::EARLY_INFO.get().unwrap().memory_regions;
 
-    for region in regions
-        .iter()
-        .rev()
-        .skip_while(|r| r.typ() != MemoryRegionType::Usable)
-    {
+    for region in regions.iter().rev().skip_while(|r| !r.typ().is_physical()) {
         match region.typ() {
             MemoryRegionType::BadMemory => mark_ranges!(region, UnusableMemoryMeta),
             MemoryRegionType::Unknown => mark_ranges!(region, ReservedMemoryMeta),