[Pedro Henrique Penna (ppenna)]

Part of #1120 (SL6.0a, "Strict snapshot reads survive the stores' removal"). Parent #1087, umbrella #1076.

What and why

SnapshotManifest::read and Snapshot::open read a snapshot's manifest and its key.bin with open_regular and read_at_most from host::store::regular. So the strict snapshot reads depended on file helpers and a refusal classification that the store owns, and #1121 deletes the store. This PR moves those helpers to the host's platform layer and switches the retained snapshot readers to it:

• open_regular, read_at_most, is_refused, the private Refused type and their regular-file support (not_regular, refused_open, regular) move from host::store::regular to host::platform, which stays. The moved code is unchanged, except that refused_open and regular become pub(crate) for the store's open_regular_in.
• regular needs is_reparse_point, which moves down from host::filesystem::host_path to host::platform and stays re-exported where it was: filesystem builds on platform, and the children of host depend on one another without cycles (tests/host_modules.rs).
• The store keeps open_regular_in, which now builds its link and non-regular-file refusals with the moved refused_open and regular. It keeps open_regular, read_at_most and is_refused as aliases for its remaining callers until nvx-rs slimming 4.2.2: the old clone path, template store and sandbox store are gone #1121 deletes them.
• SnapshotManifest::read, read_attachments, which shares its read, and Snapshot::open's read of key.bin use host::platform directly.

The maximum-length error, the refusal of links, directories and other files that are not regular files, and the refusal classification are unchanged. The public API doesn't change: every moved item is crate-private, and scripts/public_api.py finds both snapshots current. BOOT_CONTRACT_VERSION and CONTROL_CONTRACT_REVISION don't change. The issue's Scope names the manifest reader at its old path, host/template/manifest.rs, which SL2.12a moved to host/snapshot/manifest.rs.

Scope extension: Snapshot::open

The Scope names only SnapshotManifest::read, which was the only strict snapshot reader when #1120 was written. SL2.12b (#1440) then added Snapshot::open, which reads key.bin through the same store helpers. The slice's Objective says that retained readers use their new owner, so, as the orchestrator decided, this PR switches Snapshot::open as well: one import and two calls in host/snapshot.rs, which keeps the PR within its limits.

Not in this PR: callers to move before SL6.1

These retained callers still use the store's helpers and must move before SL6.1 (#1121) deletes host/store/. Besides the aliases, they use the store's private-file helpers in host::store::files (write_private, sync_dir, create_new), which this slice doesn't move, so they belong to a later slice:

• finish_capture, in host/snapshot/capture.rs: open_regular and read_at_most through the aliases, and write_private and sync_dir;
• the CLI's sandbox store, in host/cli/store/files.rs: open_regular and read_at_most through the aliases, and host::store::files;
• the CLI's capture, in host/cli/snapshots/capture.rs: create_new;
• the CLI's snapshot store, in host/cli/snapshots.rs: sync_dir.

The store and clone callers keep the aliases until their deletion, as the Scope says.

History: the first implementation

Enrique Saurez (@esaurez)'s first implementation is esaurez/slim-4.2.1-sl6.0a-20261108 (6231b876, checkpoint on #1120): one commit that moved the helpers and switched the manifest reader. This PR replays it as its only commit, with Enrique Saurez (@esaurez) as its author, and corrects it:

• its tests, which reached the store's aliases from host::platform's tests, became two platform tests without store references and a store test of open_regular_in;
• the docs of host::platform, is_refused and host::store::regular describe the new owner;
• Snapshot::open switches too, as above.

Size

Measured against feature/nvx-refactor ab7c9b5f, as against d40228be and a53a2626 before it, since the rebases left the patch unchanged: 83 core lines (estimate 150, stop 300) in 5 counted files: host/platform/mod.rs, host/store/regular.rs, host/snapshot/manifest.rs, host/snapshot.rs and host/filesystem/host_path.rs. The two test files don't count.

Tests of the area

Every existing test is kept, unchanged. These read through the moved helpers:

• host::snapshot::manifest::tests: read_reads_the_manifest_of_a_snapshot, read_refuses_a_missing_manifest_as_not_found, read_refuses_more_than_a_manifest_may_hold, read_refuses_a_directory, read_refuses_a_link, read_refuses_a_junction (Windows), read_refuses_a_fifo_without_waiting_for_a_writer (Unix), the_manifests_that_openvmm_writes_are_read and the the_attachments_* tests now read through host::platform.
• host::snapshot::tests: snapshot_open_uses_the_strict_manifest_and_bounded_key_decoders, which still refuses an oversized key, and the other snapshot_open_* tests now open keys through host::platform; so does host::snapshot::key::tests::snapshot_open_refuses_other_key_contracts_and_filesystem_tags.
• The clone path's host::template::clone::tests::keys_that_their_read_refuses_for_what_they_are_are_failures_of_the_template still classifies a link, a directory and an oversized key as refusals through the aliases, and files_that_their_paths_do_not_name_as_checked_are_refused and only_a_path_that_no_longer_names_its_supplied_file_is_the_request_s keep the refusal's message.
• The template store's links_are_refused, records_that_are_not_regular_files_fail_at_once, payloads_are_checked_as_they_are_read and links_and_unsafe_ownership_are_refused_before_the_vm_starts keep their messages.

Added:

• host::platform::tests::a_bounded_read_refuses_a_regular_file_that_holds_more_than_its_bound;
• host::platform::tests::an_open_of_a_regular_file_refuses_a_link_and_a_directory (Unix);
• host::store::tests::entries_that_are_links_or_not_regular_files_are_refused_as_the_platform_refuses_them (Linux and Windows): open_regular_in's refusals are ones that host::platform recognizes.

Validation

feature/nvx-refactor has no scripts/local_gates.py, so dev's copy selected the gates and ran them with this branch's own action commands and pinned toolchain (1.95.0; MSRV 1.89), on Windows locally and on Linux on nvx-kvm-test (KVM, virtual machine, Azure Linux 3). The full matrix ran on 67213558, based on 5947e4e8. Snapshot::open's switch came next, and the branch was then rebased onto 8b775211 (SL2.16), onto d40228be (after SL4.3 and SL6.0b), onto a53a2626 (after SL3.5a, #1466) and onto ab7c9b5f (after SL3.9, #1469), without conflicts; git range-diff shows the same patch each time, and rebase_check.py verify passed after each of the last two rebases. CI passed on 597569d5 (run 42995101590: 37 passed, 9 skipped), where cargo doc --all-features also built without warnings and a code review of the whole diff found no issue.

On the head, bb218975, based on ab7c9b5f, these ran again on Windows:

• cargo fmt --all --check, and the five Clippy runs of the Lint step, among them cargo clippy -p nvx --lib --no-default-features -- -D warnings: passed;
• the library tests that host::snapshot, host::platform, host::store and manifest select, with the clone path's refusal test: 217 passed with --all-features and 211 with the default features;
• tests/host_modules.rs (22 tests), check_test_layout.py, check_test_changes.py, and public_api.py, whose Linux and Windows snapshots are unchanged: passed.

On f5436a77, the previous head, the same library tests with host::vm, host::restore and host::cli::store added passed 285 with the default features. With --all-features, 333 passed and host::restore_driver::tests::ready_has_sixty_seconds_and_start_thirty_from_ready_for_each_pending_accept_and_read (SL4.3), which the host::restore filter also selects, failed once: in that parallel run, its activate-read case expired after 59.99996 of its 60 seconds. It passed 2 runs in 2 alone, and failed the same way, after 59.9994 seconds, in the nvx-rs / windows-latest job of feature/nvx-refactor's own push CI of a53a2626 (run 42994995631). host::restore_driver uses none of the moved helpers.

CI passed on f5436a77 (run 43050110604: 34 passed, 9 skipped, Required status check among the passed). The push-triggered Copilot Setup Steps of f5436a77 (run 43050098502), which isn't part of CI, failed in its first two attempts: its native-builds and archives steps couldn't resolve azure.archive.ubuntu.com and cdimage.ubuntu.com (Temporary failure in name resolution), as every setup run that ran from 15:36 to 16:40 UTC did, dev's among them. Once other branches' setup runs passed again, its third attempt, a rerun of the failed job, passed.

CI passed on bb218975 (run 43068922503: 34 passed, 9 skipped, Required status check among the passed), and so did its Copilot Setup Steps (run 43068910907).

Gate, on 67213558	Windows	Linux
cargo fmt --all --check	Passed	Passed
Clippy with -D warnings, the five feature sets of the Lint step	Passed	Passed
cargo test --locked --all-features	Failed: pre-existing, below	Failed: pre-existing guest::* failures, below
cargo test --locked	Failed: pre-existing flake, below	Passed
cargo build and cargo test --lib, --no-default-features	Passed	Passed
Artifact bundling	Passed	Passed
cargo doc --all-features with -D warnings	Passed	Passed
scripts/public_api.py (both snapshots)	Passed, unchanged (on 597569d5)	Passed, unchanged
MSRV: cargo +1.89 check	Passed	Passed
macOS check	-	Passed
nvx.py check-guest-binaries	-	Failed: pre-existing guest::* failures, below
nvx.py build-guest-binaries, test-guest-binaries	-	Passed
Runtime adapter: protocol-only and host-only, and guest-only on Linux	Passed	Passed
check_test_layout.py, check_markdown_links.py, check_test_changes.py	Passed	Passed
CLI checks (validate-nvx)	Failed: pre-existing script-test errors, below	Not run: the host has no pip

Every failure also fails at the base on the same host:

• Windows. Under load from parallel builds, three timing-sensitive tests fail: host::cli::snapshots::capture::tests::a_capture_ack_and_successful_output_without_timely_exit_are_stopped_but_never_finished (a 1-second capture deadline: 3 runs in 3 at the head, 2 in 3 at the base), tests/template_capture.rs's vms_that_never_end_are_torn_down_at_the_deadline (a 2-second deadline: 5 in 5 at both, run alternately), and, once in the default-feature run, host::platform::windows::tests::children_inherit_only_their_standard_handles, which passes 3 runs in 3 alone at both. With --no-fail-fast, every other unit test, integration test and doctest passes. The CLI checks' scripts/test_microvm_tests.py has 16 errors in its scenario-script tests at the head and 18 at the base; no script changes.
• Linux. With --all-features, the same 28 tests of guest::{entry, exec, init, managed_agent} fail at both revisions, and the guest musl suite of check-guest-binaries fails the same 26 at both. These tests reach none of the changed modules, which the guest build doesn't compile.

No microVM scenario ran: the change moves crate-private helpers without changing their behavior. CI runs the selected hypervisor suites on KVM, MSHV and WHP.

Changes to existing tests

python3 scripts/check_test_changes.py --base origin/feature/nvx-refactor lists no change to an existing test, and the 3 added tests above, so this PR has no tests-modified label.

The openvmm gitlink doesn't move.

[Copilot]

🟢 Approval recommended

No active review issues are reported for the relocation of strict snapshot-read helpers into the platform layer.

No open issues 🎉

What changed in this PR

Moves strict snapshot file reads into host::platform, preparing for removal of the legacy stores under #1120. The refactor preserves size limits, regular-file checks, refusal classification, and the public API.

Changes:

• Relocates bounded-read helpers and reparse-point detection to the platform layer, retaining compatibility aliases.
• Switches snapshot manifest and key readers to use the platform helpers directly.
• Adds tests for bounded reads, non-regular-file rejection, and shared refusal classification.

File	Description
nvx-rs/​src/​host/​store/​tests.rs	Tests that store-entry refusals retain platform classification.
nvx-rs/​src/​host/​store/​regular.rs	Retains aliases and delegates regular-file checks to platform helpers.
nvx-rs/​src/​host/​snapshot/​manifest.rs	Reads manifests through the platform layer.
nvx-rs/​src/​host/​snapshot.rs	Reads snapshot keys through the platform layer.
nvx-rs/​src/​host/​platform/​tests.rs	Adds bounded-read and link/directory refusal tests.
nvx-rs/​src/​host/​platform/​mod.rs	Owns strict file-read helpers and refusal classification.
nvx-rs/​src/​host/​filesystem/​host_path.rs	Re-exports reparse-point detection from its new platform owner.

_{Review effort: Balanced}