feat(virtq): use Rc pointer equality instead if generation for pools by andreiltd · Pull Request #1945 · hyperlight-dev/hyperlight

andreiltd · 2026-10-16T12:10:15Z

Instead of threading generation through pools it's actually simpler to use Rc::ptr_eq to check if pool belongs to current snapshot generation and swap pools on restore.

Copilot

🟡 Changes recommended

Reservation validation rejects every nonempty pool swap, causing restore failures with retained buffers and posted chains.

1 open finding

Validate retained addresses against current pool before reserving · New

What changed in this PR

This PR uses shared pool identity to track virtqueue allocation ownership across snapshot restores.

Changes:

Replace pool generation counters with Rc pointer identity and pool swaps.
Keep retained leases tied to their original pools.
Expand swap tests and update transport documentation.

File	Description
src/hyperlight_host/tests/integration_test.rs	Rename the retained-buffer test.
src/hyperlight_guest/src/transport/context.rs	Clarify pool ownership and restore safety comments.
src/hyperlight_guest/src/transport/backing.rs	Update alias allocator terminology.
src/hyperlight_common/src/virtq/producer.rs	Swap pools while preserving posted chains.
src/hyperlight_common/src/virtq/pool/tests.rs	Test swap reservations, ordering, and validation.
src/hyperlight_common/src/virtq/pool/slot.rs	Implement pool identity and replacement allocation state.
src/hyperlight_common/src/virtq/buffer.rs	Return leases to their original pools.
docs/virtio-host-guest-communication.md	Document pool swaps and retained ownership.

🧠 Review effort: Balanced

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

Instead of threading generation through pools it's actually simpler to use Rc::ptr_eq to check if pool belongs to current snapshot generation and swap pools on restore. Signed-off-by: Tomasz Andrzejak <andreiltd@gmail.com>

hyperlight-gh-bot · 2026-10-20T17:54:38Z

Benchmark Results

Measured commit: 7e26042c3a33
Baseline commit: f0934723ebf0

kvm / amd (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`751.77 ns` (➖ 1.01x slower)
`vec_bytes`	`581.53 ns` (➖ 1.00x faster)
		`382.00 µs` (➖ 1.02x slower)

payload_allocation

	`slot_pool_segmented`
`65536`	`145.10 ns` (➖ 1.19x faster)
`262144`	`521.77 ns` (➖ 1.01x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`83.98 ms` (➖ 1.01x slower)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`7.76 ns` (➖ 1.00x faster)	`7.77 ns` (➖ 1.01x slower)	`7.77 ns` (➖ 1.00x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`93.06 µs` (➖ 1.00x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`2.11 µs` (➖ 1.09x slower)	`1.98 µs` (➖ 1.06x faster)
`262144`	`7.73 µs` (➖ 1.10x slower)	`6.95 µs` (➖ 1.06x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`6.54 µs` (➖ 1.03x faster)	`6.19 µs` (➖ 1.06x faster)
`8192`	`1.06 µs` (➖ 1.05x faster)	`1.06 µs` (➖ 1.01x slower)
`262144`		`28.20 µs` (➖ 1.02x slower)

kvm / intel (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`695.29 ns` (➖ 1.02x faster)
`vec_bytes`	`500.50 ns` (➖ 1.03x faster)
		`656.36 µs` (➖ 1.01x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`152.29 ns` (➖ 1.12x slower)
`262144`	`514.85 ns` (➖ 1.02x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`75.89 ms` (➖ 1.01x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`7.06 ns` (➖ 1.02x faster)	`7.00 ns` (➖ 1.02x faster)	`6.96 ns` (➖ 1.02x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`45.73 µs` (➖ 1.00x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`2.12 µs` (➖ 1.01x slower)	`2.10 µs` (➖ 1.01x faster)
`262144`	`7.59 µs` (➖ 1.01x slower)	`7.51 µs` (➖ 1.00x slower)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`6.94 µs` (➖ 1.06x faster)	`7.04 µs` (➖ 1.04x faster)
`8192`	`740.86 ns` (➖ 1.05x faster)	`721.70 ns` (➖ 1.04x faster)
`262144`		`30.73 µs` (➖ 1.03x faster)

mshv3 / amd (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`941.46 ns` (➖ 1.02x slower)
`vec_bytes`	`711.56 ns` (➖ 1.02x slower)
		`315.34 µs` (➖ 1.02x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`185.75 ns` (➖ 1.02x slower)
`262144`	`670.13 ns` (➖ 1.00x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`60.16 ms` (➖ 1.06x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`9.95 ns` (➖ 1.03x faster)	`10.30 ns` (➖ 1.04x slower)	`9.91 ns` (➖ 1.00x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`86.23 µs` (➖ 1.01x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`2.63 µs` (➖ 1.02x faster)	`2.50 µs` (➖ 1.02x slower)
`262144`	`9.02 µs` (➖ 1.02x faster)	`9.05 µs` (➖ 1.01x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`8.10 µs` (➖ 1.03x faster)	`7.99 µs` (➖ 1.02x faster)
`8192`	`1.52 µs` (➖ 1.11x slower)	`1.31 µs` (➖ 1.01x faster)
`262144`		`34.89 µs` (➖ 1.02x faster)

mshv3 / intel (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`929.97 ns` (➖ 1.01x faster)
`vec_bytes`	`746.17 ns` (➖ 1.13x slower)
		`696.35 µs` (➖ 1.01x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`171.67 ns` (➖ 1.02x faster)
`262144`	`640.88 ns` (➖ 1.02x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`66.80 ms` (➖ 1.01x slower)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`8.82 ns` (➖ 1.08x faster)	`8.82 ns` (➖ 1.06x faster)	`8.84 ns` (➖ 1.10x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`48.36 µs` (➖ 1.09x slower)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`2.28 µs` (➖ 1.00x slower)	`2.32 µs` (➖ 1.03x slower)
`262144`	`7.99 µs` (➖ 1.02x faster)	`7.96 µs` (➖ 1.01x slower)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`7.50 µs` (➖ 1.01x faster)	`7.43 µs` (➖ 1.04x faster)
`8192`	`900.85 ns` (➖ 1.07x faster)	`916.64 ns` (➖ 1.00x faster)
`262144`		`39.95 µs` (➖ 1.00x slower)

hyperv-ws2025 / amd (Windows) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`1.15 µs` (➖ 1.01x slower)
`vec_bytes`	`786.95 ns` (➖ 1.01x slower)
		`1.85 ms` (➖ 1.01x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`239.98 ns` (➖ 1.02x slower)
`262144`	`796.35 ns` (➖ 1.02x slower)

sandboxes

	`create_initialized_and_drop`
`medium`	`78.39 ms` (➖ 1.06x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`10.93 ns` (➖ 1.08x faster)	`10.15 ns` (➖ 1.08x faster)	`10.11 ns` (➖ 1.05x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`698.73 µs` (➖ 1.10x slower)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`2.38 µs` (➖ 1.01x faster)	`2.34 µs` (➖ 1.01x slower)
`262144`	`9.04 µs` (➖ 1.07x faster)	`9.14 µs` (➖ 1.02x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`9.93 µs` (➖ 1.09x slower)	`8.80 µs` (➖ 1.00x slower)
`8192`	`1.30 µs` (➖ 1.09x faster)	`1.30 µs` (➖ 1.01x faster)
`262144`		`40.06 µs` (➖ 1.04x slower)

hyperv-ws2025 / intel (Windows) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`1.19 µs` (➖ 1.01x slower)
`vec_bytes`	`769.48 ns` (➖ 1.00x faster)
		`2.91 ms` (➖ 1.04x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`216.03 ns` (➖ 1.02x slower)
`262144`	`765.15 ns` (➖ 1.00x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`105.72 ms` (➖ 1.02x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`11.10 ns` (➖ 1.10x slower)	`10.19 ns` (➖ 1.01x faster)	`10.90 ns` (➖ 1.08x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`574.17 µs` (➖ 1.11x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`2.39 µs` (➖ 1.03x slower)	`2.33 µs` (➖ 1.02x faster)
`262144`	`7.80 µs` (➖ 1.02x slower)	`7.81 µs` (➖ 1.00x slower)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`8.44 µs` (➖ 1.02x faster)	`8.37 µs` (➖ 1.07x faster)
`8192`	`1.14 µs` (➖ 1.09x faster)	`1.09 µs` (➖ 1.02x faster)
`262144`		`44.11 µs` (➖ 1.03x slower)

_{Reported by cargo ci bench-report --candidate run:39464068872 --config-file bench_report.toml.}

Copilot AI balanced review requested due to automatic review settings October 16, 2026 12:10

andreiltd requested review from danbugs, dblnz, devigned, jprendes, jsturtevant, ludfjig, simongdavies, squillace and syntactically as code owners October 16, 2026 12:10

andreiltd added the kind/refactor For PRs that restructure or remove code without adding new functionality. label Oct 16, 2026

Copilot started reviewing on behalf of andreiltd October 16, 2026 12:11

View session

andreiltd changed the title ~~feat(virtq): use Rc pointer equality instead generation for pools~~ feat(virtq): use Rc pointer equality instead if generation for pools Oct 16, 2026

Copilot AI reviewed Oct 16, 2026

View reviewed changes

Comment thread src/hyperlight_common/src/virtq/pool/slot.rs

andreiltd force-pushed the virtq-pool-inst branch from 6b8cdb4 to 2940278 Compare October 19, 2026 12:01

This comment has been minimized.

Sign in to view

andreiltd force-pushed the virtq-pool-inst branch 3 times, most recently from 4062922 to 97d57b1 Compare October 19, 2026 14:25

This comment has been minimized.

Sign in to view

feat(virtq): use Rc ptr equality instead generation for pools

7e26042

Instead of threading generation through pools it's actually simpler to use Rc::ptr_eq to check if pool belongs to current snapshot generation and swap pools on restore. Signed-off-by: Tomasz Andrzejak <andreiltd@gmail.com>

andreiltd force-pushed the virtq-pool-inst branch from 97d57b1 to 7e26042 Compare October 20, 2026 17:12

Conversation

andreiltd commented Oct 16, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

hyperlight-gh-bot Bot commented Oct 20, 2026

Benchmark Results

Benchmark Results

function_call_codec

payload_allocation

sandboxes

slot_pool

snapshot_files

virtq_readonly

virtq_readwrite

Benchmark Results

function_call_codec

payload_allocation

sandboxes

slot_pool

snapshot_files

virtq_readonly

virtq_readwrite

Benchmark Results

function_call_codec

payload_allocation

sandboxes

slot_pool

snapshot_files

virtq_readonly

virtq_readwrite

Benchmark Results

function_call_codec

payload_allocation

sandboxes

slot_pool

snapshot_files

virtq_readonly

virtq_readwrite

Benchmark Results

function_call_codec

payload_allocation

sandboxes

slot_pool

snapshot_files

virtq_readonly

virtq_readwrite

Benchmark Results

function_call_codec

payload_allocation

sandboxes

slot_pool

snapshot_files

virtq_readonly

virtq_readwrite

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants