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.

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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 · 2026-10-19T15:10:57Z

Benchmark Results

Measured commit: 97d57b1900a4
Baseline commit: 8a311248f0ab

kvm / amd (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`761.44 ns` (➖ 1.00x faster)
`vec_bytes`	`582.34 ns` (➖ 1.02x faster)
		`377.11 µs` (➖ 1.01x slower)

payload_allocation

	`slot_pool_segmented`
`262144`	`553.46 ns` (➖ 1.30x faster)
`65536`	`142.65 ns` (➖ 1.01x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`82.08 ms` (➖ 1.01x slower)

slot_pool

	`alloc_dealloc_1500`	`alloc_dealloc_4096`	`alloc_dealloc_128`
	`7.86 ns` (➖ 1.00x slower)	`7.72 ns` (➖ 1.04x faster)	`7.72 ns` (➖ 1.00x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`93.66 µs` (➖ 1.01x slower)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`262144`	`7.02 µs` (➖ 1.46x faster)	`7.42 µs` (➖ 1.16x faster)
`65536`	`2.05 µs` (➖ 1.06x slower)	`1.92 µs` (➖ 1.10x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`6.33 µs` (➖ 1.03x faster)	`6.94 µs` (➖ 1.04x slower)
`8192`	`1.14 µs` (➖ 1.08x slower)	`1.04 µs` (➖ 1.04x faster)
`262144`		`28.62 µs` (➖ 1.03x slower)

kvm / intel (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`791.26 ns` (➖ 1.04x faster)
`vec_bytes`	`594.18 ns` (➖ 1.04x faster)
		`719.92 µs` (➖ 1.03x faster)

payload_allocation

	`slot_pool_segmented`
`262144`	`604.55 ns` (➖ 1.04x faster)
`65536`	`161.15 ns` (➖ 1.00x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`83.27 ms` (➖ 1.02x slower)

slot_pool

	`alloc_dealloc_1500`	`alloc_dealloc_4096`	`alloc_dealloc_128`
	`8.17 ns` (➖ 1.02x faster)	`8.10 ns` (➖ 1.03x faster)	`8.26 ns` (➖ 1.03x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`50.43 µs` (➖ 1.01x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`262144`	`8.93 µs` (➖ 1.01x faster)	`8.73 µs` (➖ 1.04x faster)
`65536`	`2.47 µs` (➖ 1.02x faster)	`2.47 µs` (➖ 1.02x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`8.15 µs` (➖ 1.08x faster)	`8.12 µs` (➖ 1.08x faster)
`8192`	`870.39 ns` (➖ 1.08x faster)	`860.77 ns` (➖ 1.06x faster)
`262144`		`36.23 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`	`933.67 ns` (➖ 1.01x faster)
`vec_bytes`	`712.15 ns` (➖ 1.00x faster)
		`315.97 µs` (➖ 1.00x faster)

payload_allocation

	`slot_pool_segmented`
`262144`	`678.74 ns` (➖ 1.01x slower)
`65536`	`188.12 ns` (➖ 1.03x slower)

sandboxes

	`create_initialized_and_drop`
`medium`	`58.12 ms` (➖ 1.00x faster)

slot_pool

	`alloc_dealloc_1500`	`alloc_dealloc_4096`	`alloc_dealloc_128`
	`9.96 ns` (➖ 1.00x slower)	`9.94 ns` (➖ 1.01x faster)	`9.95 ns` (➖ 1.00x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`86.30 µs` (➖ 1.01x slower)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`262144`	`9.14 µs` (➖ 1.01x faster)	`9.21 µs` (➖ 1.10x faster)
`65536`	`2.64 µs` (➖ 1.04x faster)	`2.46 µs` (➖ 1.00x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`8.00 µs` (➖ 1.06x faster)	`8.03 µs` (➖ 1.03x faster)
`8192`	`1.39 µs` (➖ 1.01x faster)	`1.34 µs` (➖ 1.01x faster)
`262144`		`35.21 µs` (➖ 1.01x faster)

mshv3 / intel (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`970.14 ns` (➖ 1.06x slower)
`vec_bytes`	`659.71 ns` (➖ 1.02x faster)
		`702.81 µs` (➖ 1.46x faster)

payload_allocation

	`slot_pool_segmented`
`262144`	`637.07 ns` (➖ 1.04x faster)
`65536`	`172.10 ns` (➖ 1.00x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`66.20 ms` (➖ 1.09x faster)

slot_pool

	`alloc_dealloc_1500`	`alloc_dealloc_4096`	`alloc_dealloc_128`
	`8.79 ns` (➖ 1.10x faster)	`9.51 ns` (➖ 1.01x slower)	`8.86 ns` (➖ 1.07x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`49.63 µs` (➖ 1.00x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`262144`	`8.01 µs` (➖ 1.00x slower)	`7.94 µs` (➖ 1.00x faster)
`65536`	`2.34 µs` (➖ 1.02x slower)	`2.29 µs` (➖ 1.00x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`7.48 µs` (➖ 1.02x faster)	`7.44 µs` (➖ 1.05x faster)
`8192`	`922.70 ns` (➖ 1.02x faster)	`913.31 ns` (➖ 1.00x faster)
`262144`		`37.12 µs` (➖ 1.16x faster)

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 faster)
`vec_bytes`	`784.69 ns` (➖ 1.00x slower)
		`2.01 ms` (➖ 1.00x faster)

payload_allocation

	`slot_pool_segmented`
`262144`	`792.48 ns` (➖ 1.00x slower)
`65536`	`232.40 ns` (➖ 1.03x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`87.56 ms` (➖ 1.00x faster)

slot_pool

	`alloc_dealloc_1500`	`alloc_dealloc_4096`	`alloc_dealloc_128`
	`11.11 ns` (➖ 1.09x slower)	`10.15 ns` (➖ 1.04x faster)	`9.90 ns` (➖ 1.02x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`662.09 µs` (➖ 1.17x faster)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`262144`	`9.56 µs` (➖ 1.04x slower)	`9.61 µs` (➖ 1.07x slower)
`65536`	`2.42 µs` (➖ 1.02x slower)	`2.38 µs` (➖ 1.02x slower)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`9.11 µs` (➖ 1.01x faster)	`8.82 µs` (➖ 1.01x faster)
`8192`	`1.37 µs` (➖ 1.01x faster)	`1.30 µs` (➖ 1.02x faster)
`262144`		`39.63 µs` (➖ 1.06x faster)

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

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`encode_control`	`decode_vec_bytes_copy`
`byte_chunks`	`1.22 µs` (➖ 1.00x slower)
`vec_bytes`	`808.40 ns` (➖ 1.04x faster)
		`4.18 ms` (➖ 1.06x faster)

payload_allocation

	`slot_pool_segmented`
`262144`	`748.26 ns` (➖ 1.01x faster)
`65536`	`216.72 ns` (➖ 1.01x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`127.49 ms` (➖ 1.15x faster)

slot_pool

	`alloc_dealloc_1500`	`alloc_dealloc_4096`	`alloc_dealloc_128`
	`10.38 ns` (➖ 1.04x slower)	`10.12 ns` (➖ 1.01x slower)	`10.47 ns` (➖ 1.05x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`615.42 µs` (➖ 1.01x slower)

virtq_readonly

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`262144`	`7.82 µs` (➖ 1.00x faster)	`7.84 µs` (➖ 1.01x faster)
`65536`	`2.34 µs` (➖ 1.00x faster)	`2.35 µs` (➖ 1.01x faster)

virtq_readwrite

	`slot_pool_segmented_fragmented`	`slot_pool_segmented`
`65536`	`8.35 µs` (➖ 1.06x faster)	`8.42 µs` (➖ 1.06x faster)
`8192`	`1.10 µs` (➖ 1.16x faster)	`1.08 µs` (➖ 1.04x faster)
`262144`		`41.83 µs` (➖ 1.10x faster)

_{Reported by cargo ci bench-report --candidate run:39268798918 --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

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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

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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

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andreiltd force-pushed the virtq-pool-inst branch 2 times, most recently from 8de61b5 to 4062922 Compare October 19, 2026 13:47

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

97d57b1

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 4062922 to 97d57b1 Compare October 19, 2026 14:25

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andreiltd commented Oct 16, 2026

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hyperlight-gh-bot Bot commented Oct 19, 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

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