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loader: update the page table builder to be no_std #2062

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loader: update the page table builder to be no_std #2062

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48aad4b
no_std page table builder
babayet2 Sep 15, 2025
aeb9776
allocate space up front, remove generics
babayet2 Oct 8, 2025
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1 change: 0 additions & 1 deletion Cargo.lock
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Original file line number Diff line number Diff line change
Expand Up @@ -5287,7 +5287,6 @@ name = "page_table"
version = "0.0.0"
dependencies = [
"bitfield-struct 0.11.0",
"tracing",
"zerocopy 0.8.25",
]

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2 changes: 1 addition & 1 deletion vm/loader/manifests/openhcl-x64-cvm-dev.json
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Expand Up @@ -57,4 +57,4 @@
}
}
]
}
}
1 change: 0 additions & 1 deletion vm/loader/page_table/Cargo.toml
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Expand Up @@ -8,7 +8,6 @@ rust-version.workspace = true

[dependencies]
bitfield-struct.workspace = true
tracing.workspace = true
zerocopy.workspace = true
[lints]
workspace = true
23 changes: 5 additions & 18 deletions vm/loader/page_table/src/aarch64.rs
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Expand Up @@ -437,10 +437,6 @@ impl<'a> Arm64PageTableSpace<'a> {
debug_assert!(aligned(phys_table_start, Arm64PageSize::Small));
debug_assert!(index < PAGE_SIZE_4K as usize / size_of::<Arm64PageTableEntry>());

tracing::debug!(
"Writing page table entry {entry:#016x}, index {index:#x}, table {phys_table_start:#x}"
);

let pos = phys_table_start as usize - self.phys_page_table_root
+ index * size_of::<Arm64PageTableEntry>();
self.space[pos..pos + 8].copy_from_slice(&entry.to_le_bytes());
Expand Down Expand Up @@ -677,13 +673,13 @@ impl<'a> Arm64PageTableSpace<'a> {
}

/// Build a set of Aarch64 page tables identity mapping the given region.
pub fn build_identity_page_tables_aarch64(
pub fn build_identity_page_tables_aarch64<'a>(
page_table_gpa: u64,
start_gpa: u64,
size: u64,
memory_attribute_indirection: MemoryAttributeIndirectionEl1,
page_table_region_size: usize,
) -> Vec<u8> {
page_table_space: &'a mut [u8],
) -> &'a [u8] {
// start_gpa and size must be 2MB aligned.
if !aligned(start_gpa, Arm64PageSize::Large) {
panic!("start_gpa not 2mb aligned");
Expand All @@ -693,13 +689,8 @@ pub fn build_identity_page_tables_aarch64(
panic!("size not 2mb aligned");
}

tracing::debug!(
"Creating Aarch64 page tables at {page_table_gpa:#x} mapping starting at {start_gpa:#x} of size {size} bytes"
);

let mut page_table_space = vec![0; page_table_region_size];
let mut page_tables =
Arm64PageTableSpace::new(page_table_gpa as usize, &mut page_table_space).unwrap();
Arm64PageTableSpace::new(page_table_gpa as usize, page_table_space).unwrap();
page_tables
.map_range(
start_gpa,
Expand All @@ -713,12 +704,8 @@ pub fn build_identity_page_tables_aarch64(
.unwrap();

let used_space = page_tables.used_space();
tracing::debug!("Page tables use {used_space} bytes");
tracing::debug!("Page tables stats by level: {:?}", page_tables.lvl_stats());

page_table_space.truncate(used_space);

page_table_space
&page_table_space[0..used_space]
}

#[cfg(test)]
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1 change: 1 addition & 0 deletions vm/loader/page_table/src/lib.rs
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Expand Up @@ -3,6 +3,7 @@

//! Methods to construct page tables.

#![no_std]
#![expect(missing_docs)]
#![forbid(unsafe_code)]

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