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Do some miscellaneous page table cleanups

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This commit is contained in:
Ruihan Li
2025-06-19 12:46:28 +08:00
committed by Junyang Zhang
parent 11f9675f37
commit a1accf4304
6 changed files with 128 additions and 101 deletions
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20
ostd/src/mm/page_table/node/mod.rs
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@ -225,15 +225,14 @@ impl<'rcu, C: PageTableConfig> PageTableGuard<'rcu, C> {
///
/// This operation will leak the old child if the old PTE is present.
///
/// The child represented by the given PTE will handover the ownership to
/// the node. The PTE will be rendered invalid after this operation.
///
/// # Safety
///
/// The caller must ensure that:
/// 1. The index must be within the bound;
/// 2. The PTE must represent a valid [`Child`] whose level is compatible
/// with the page table node.
/// 2. The PTE must represent a [`Child`] in the same [`PageTableConfig`]
/// and at the right paging level (`self.level() - 1`).
/// 3. The page table node will have the ownership of the [`Child`]
/// after this method.
pub(super) unsafe fn write_pte(&mut self, idx: usize, pte: C::E) {
debug_assert!(idx < nr_subpage_per_huge::<C>());
let ptr = paddr_to_vaddr(self.start_paddr()) as *mut C::E;
@ -296,24 +295,25 @@ impl<C: PageTableConfig> PageTablePageMeta<C> {
}
}
// SAFETY: We can read the page table node because the page table pages are
// accessed as untyped memory.
// FIXME: The safe APIs in the `page_table/node` module allow `Child::Frame`s with
// arbitrary addresses to be stored in the page table nodes. Therefore, they may not
// be valid `C::Item`s. The soundness of the following `on_drop` implementation must
// be reasoned in conjunction with the `page_table/cursor` implementation.
unsafe impl<C: PageTableConfig> AnyFrameMeta for PageTablePageMeta<C> {
fn on_drop(&mut self, reader: &mut VmReader<Infallible>) {
let nr_children = self.nr_children.get_mut();
if *nr_children == 0 {
return;
}
let level = self.level;
// Drop the children.
let range = if level == C::NR_LEVELS {
C::TOP_LEVEL_INDEX_RANGE.clone()
} else {
0..nr_subpage_per_huge::<C>()
};
// Drop the children.
reader.skip(range.start * size_of::<C::E>());
for _ in range {
// Non-atomic read is OK because we have mutable access.