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Pin hyperlight-host and hyperlight-common to hyperlight's scratch-resize branch, and point the kernel submodule at the scratch-resize branch of the danbugs/unikraft fork (off plat-hyperlight-v2). A hyperlight release and the upstream kernel branch replace both before this merges. Signed-off-by: danbugs <danilochiarlone@gmail.com>
Bump the kernel to the scratch-resize branch (plat-hyperlight-v2 c1051427 -> 11e01f8a), and rebuild the kernels and the native-kernel fixture: - The allocator stopped two pages below the top of scratch, but Hyperlight reserves twelve there, and the early fault handlers had no limit. Allocation now stops at the reserved pages, or at the transport arena when the host places it below them. - A guest that ran out of scratch inside a copy-on-write fault crashed again reporting it and triple-faulted the VM. It now aborts. - The scratch base follows the scratch size, so the kernel runs from a snapshot restored with less scratch. The kernel runs on hyperlight 0.18.0 as well as on the scratch-resize host. Signed-off-by: danbugs <danilochiarlone@gmail.com>
Booting needs room to unpack the rootfs; guest function calls need far less. snapshot_with_scratch_mb takes a snapshot that a sandbox restores with `mb` MiB of scratch, so every restore of a warm image costs less. It errors on a size above the sandbox's scratch or too small for the transport and page tables; a size too small for the kernel fails the restore, and a restore of a snapshot that fits recovers the sandbox. The host's scratch layout changed (the transport arena sits at a fixed address below the top of scratch), so SNAPSHOT_CONTRACT goes to 6 and older snapshots are refused. tests/resize.rs covers the round trip, the error paths and a guest function call that outgrows the snapshot; the arm64 job runs it too. Signed-off-by: danbugs <danilochiarlone@gmail.com>
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🔵 Needs a closer look
Snapshot memory-layout changes depend on unmerged host and kernel work and require final human validation.
No open issues 🎉
What changed in this PR
Adds smaller-scratch snapshots so guests can boot with ample memory and restore with less, reducing restore costs.
Changes:
- Adds
snapshot_with_scratch_mband documents sizing and recovery behavior. - Tests resized snapshots, persistence, and failure recovery.
- Updates snapshot compatibility and temporarily pins unmerged host and kernel dependencies.
| File | Description |
|---|---|
| tests/resize.rs | Tests resizing, persistence, limits, and recovery. |
| src/lib.rs | Adds the resized-snapshot API and saturating size conversion. |
| docs/execution.md | Documents smaller-scratch restores. |
| CHANGELOG.md | Records the API and compatibility changes. |
| Cargo.toml | Pins experimental Hyperlight dependencies. |
| Cargo.lock | Locks the pinned Hyperlight revision. |
| build.rs | Bumps the snapshot contract to 6. |
| .gitmodules | Selects the scratch-resize kernel fork. |
| .github/workflows/arm64.yml | Includes resize tests in arm64 CI. |
Review effort: Balanced
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Adds
AppSandbox::snapshot_with_scratch_mb: boot with the scratch unpacking the rootfs needs, then restore guest function calls from a snapshot with far less. Built against hyperlight'sscratch-resizebranch (hyperlight-dev/hyperlight#1947) and a kernel branch on a fork, so it can't merge until both land upstream.snapshot_with_scratch_mb,SNAPSHOT_CONTRACT6,tests/resize.rs(also run in the arm64 job), plus CHANGELOG and execution docs.