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Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>
Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>
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Save snapshots to disk via Snapshot::to_file(), load them back via Snapshot::from_file(). Create sandboxes directly from loaded snapshots via MultiUseSandbox::from_snapshot(), bypassing ELF parsing and guest init. Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>
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Pull request overview
Adds first-class support for persisting Snapshots to disk and rehydrating sandboxes from those snapshots to avoid ELF parsing / guest init on cold start, using file-backed mappings for (near) zero-copy loads.
Changes:
- Implement
Snapshot::to_file(),Snapshot::from_file(), andSnapshot::from_file_unchecked()with a versioned on-disk header + mmappable memory blob. - Add
MultiUseSandbox::from_snapshot()fast-path for sandbox creation directly from an in-memory or disk-loaded snapshot. - Introduce file-backed
ReadonlySharedMemory::from_file()and refactorSandboxMemoryLayoutto expose enough stable layout fields for serialization.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| src/hyperlight_host/src/sandbox/uninitialized_evolve.rs | Updates layout API usage (peb_address() accessor). |
| src/hyperlight_host/src/sandbox/uninitialized.rs | Ensures snapshot-based sandbox creation registers default HostPrint via FunctionRegistry::with_default_host_print(). |
| src/hyperlight_host/src/sandbox/snapshot.rs | Defines snapshot file format + (de)serialization, file load/save APIs, sregs I/O, and extensive tests. |
| src/hyperlight_host/src/sandbox/initialized_multi_use.rs | Adds MultiUseSandbox::from_snapshot() instantiation path. |
| src/hyperlight_host/src/sandbox/host_funcs.rs | Adds FunctionRegistry::with_default_host_print() helper and makes default writer private. |
| src/hyperlight_host/src/mem/shared_mem.rs | Adds ReadonlySharedMemory::from_file() for file-backed snapshot memory mappings. |
| src/hyperlight_host/src/mem/mgr.rs | Updates layout field access for scratch I/O buffer sizes. |
| src/hyperlight_host/src/mem/memory_region.rs | Routes Snapshot regions through the Windows surrogate “ReadOnlyFile” mapping path. |
| src/hyperlight_host/src/mem/layout.rs | Refactors SandboxMemoryLayout to store key sizes directly and computes offsets via methods; updates PEB writing. |
| src/hyperlight_host/src/hypervisor/hyperlight_vm/x86_64.rs | Factors out apply_sregs() and updates peb_address() usage. |
| src/hyperlight_host/benches/benchmarks.rs | Adds benchmarks for snapshot file save/load and cold start via snapshot. |
| src/hyperlight_common/src/mem.rs | Adds write_to() helpers for GuestMemoryRegion and HyperlightPEB. |
| docs/snapshot-file-implementation-plan.md | Adds a detailed design/format plan and future work notes. |
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| fn write_sregs(w: &mut impl std::io::Write, sregs: &CommonSpecialRegisters) -> crate::Result<()> { | ||
| // Segment registers: cs, ds, es, fs, gs, ss, tr, ldt (13 fields each) | ||
| for seg in [ | ||
| &sregs.cs, &sregs.ds, &sregs.es, &sregs.fs, &sregs.gs, &sregs.ss, &sregs.tr, &sregs.ldt, | ||
| ] { |
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| let input_data_size = read_u64(r)? as usize; | ||
| let output_data_size = read_u64(r)? as usize; | ||
| let heap_size = read_u64(r)? as usize; | ||
| let code_size = read_u64(r)? as usize; | ||
| let init_data_size = read_u64(r)? as usize; |
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| Some( | ||
| MemoryRegionFlags::from_bits(perms_raw as u32).ok_or_else(|| { | ||
| crate::new_error!( | ||
| "snapshot contains unknown memory region flags: {:#x}", | ||
| perms_raw | ||
| ) | ||
| })?, | ||
| ) |
| } else { | ||
| None | ||
| }; | ||
|
|
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| /// - **Windows**: `CreateFileMappingA(PAGE_WRITECOPY)` + | ||
| /// `MapViewOfFile(FILE_MAP_COPY)` for zero-copy file-backed CoW. | ||
| /// The returned `HostMapping` carries the file mapping handle so | ||
| /// the surrogate process can create its own view via | ||
| /// `MapViewOfFileNuma2`. |
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Save snapshots to disk via
Snapshot::to_file(), load them viaSnapshot::from_file(). Create sandboxes directly from loaded snapshots viaMultiUseSandbox::from_snapshot(), bypassing ELF parsing and guest init. No memcpy needed!With this PR I'm hoping to gather feedback on design, and also start a discussion about what features is necessary before we can release this. For example currently it's impossible to register any host functions on sandboxes created directly from snapshots, and probably a builder pattern could fix this (something like
.with_host_func(hostfunc))