fix(guest): allow guest functions with more than 11 parameters by ludfjig · Pull Request #1998 · hyperlight-dev/hyperlight

ludfjig · 2026-10-29T21:46:06Z

Guest functions register with up to 32 parameters, but verify_parameters rejected every call with more than 11. This removes the limit. The guest still rejects a call whose argument count differs from the function's parameter count.

Tests:

A 32-parameter guest function, called from a host test.
Doctests on ParameterTuple: 32 parameters compile, 33 do not.

Fixes #1996

Registration accepts guest functions with up to 32 parameters, but verify_parameters rejected every call with more than 11. Remove the limit. The guest still rejects a call whose argument count differs from the function's parameter count. Add a 32-parameter guest function test, and doctests that 32 parameters compile and 33 do not. Fixes hyperlight-dev#1996 Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>

Copilot

🟢 Approval recommended

No active review issues remain for the change extending guest-call support to 32 parameters.

No open issues 🎉

What changed in this PR

This PR fixes #1996 by allowing guest calls beyond 11 parameters, matching registration’s 32-parameter support. Signature validation still rejects mismatched argument counts.

Changes:

Removes the 11-parameter runtime limit.
Adds a 32-argument integration test and doctests for the 32/33-parameter boundary.
Documents the supported limit and records the fix in the changelog.

File	Description
`src/tests/rust_guests/simpleguest/src/main.rs`	Adds a 32-parameter guest function for testing.
`src/hyperlight_host/tests/sandbox_host_tests.rs`	Tests a host call with 32 arguments.
`src/hyperlight_guest_macro/src/lib.rs`	Documents the 32-parameter limit.
`src/hyperlight_guest_bin/src/guest_function/definition.rs`	Removes the 11-parameter rejection while preserving signature checks.
`src/hyperlight_common/src/func/param_type.rs`	Adds doctests accepting 32 parameters and rejecting 33.
`CHANGELOG.md`	Records the guest-call fix.

_{Review effort: Balanced}

hyperlight-gh-bot · 2026-10-29T22:31:21Z

Benchmark Results

Measured commit: 21b6ebaa66f9
Baseline commit: 3233086b0243

kvm / amd (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`decode_vec_bytes_copy`	`encode_control`
	`372.00 µs` (➖ 1.00x slower)
`byte_chunks`		`761.98 ns` (➖ 1.03x faster)
`vec_bytes`		`590.07 ns` (➖ 1.01x slower)

payload_allocation

	`slot_pool_segmented`
`65536`	`142.58 ns` (➖ 1.02x faster)
`262144`	`538.03 ns` (➖ 1.02x slower)

sandboxes

	`create_initialized_and_drop`
`medium`	`81.06 ms` (➖ 1.00x slower)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`7.68 ns` (➖ 1.00x faster)	`7.74 ns` (➖ 1.01x slower)	`8.63 ns` (➖ 1.12x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`94.22 µs` (➖ 1.02x slower)

virtq_readonly

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`65536`	`1.97 µs` (➖ 1.06x faster)	`2.03 µs` (➖ 1.07x slower)
`262144`	`7.09 µs` (➖ 1.02x slower)	`7.04 µs` (➖ 1.01x faster)

virtq_readwrite

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`8192`	`1.05 µs` (➖ 1.01x slower)	`1.03 µs` (➖ 1.02x slower)
`65536`	`6.16 µs` (➖ 1.07x faster)	`6.46 µs` (➖ 1.01x faster)
`262144`	`27.09 µs` (➖ 1.01x faster)

kvm / intel (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`decode_vec_bytes_copy`	`encode_control`
	`744.24 µs` (➖ 1.04x slower)
`byte_chunks`		`805.32 ns` (➖ 1.06x slower)
`vec_bytes`		`580.36 ns` (➖ 1.02x slower)

payload_allocation

	`slot_pool_segmented`
`65536`	`166.79 ns` (➖ 1.19x faster)
`262144`	`546.12 ns` (➖ 1.04x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`81.06 ms` (➖ 1.02x slower)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`7.46 ns` (➖ 1.03x faster)	`7.46 ns` (➖ 1.03x faster)	`7.43 ns` (➖ 1.04x faster)

snapshot_files

	`load_snapshot_unverified`
`small`	`49.05 µs` (➖ 1.01x slower)

virtq_readonly

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`65536`	`2.43 µs` (➖ 1.02x slower)	`2.46 µs` (➖ 1.01x slower)
`262144`	`8.43 µs` (➖ 1.01x faster)	`8.55 µs` (➖ 1.01x slower)

virtq_readwrite

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`8192`	`834.33 ns` (➖ 1.03x slower)	`824.17 ns` (➖ 1.00x faster)
`65536`	`7.97 µs` (➖ 1.04x faster)	`8.45 µs` (➖ 1.04x slower)
`262144`	`35.82 µs` (➖ 1.08x slower)

mshv3 / amd (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`decode_vec_bytes_copy`	`encode_control`
	`311.83 µs` (➖ 1.10x faster)
`byte_chunks`		`949.05 ns` (➖ 1.03x slower)
`vec_bytes`		`746.98 ns` (➖ 1.06x slower)

payload_allocation

	`slot_pool_segmented`
`65536`	`194.77 ns` (➖ 1.00x slower)
`262144`	`731.10 ns` (➖ 1.00x slower)

sandboxes

	`create_initialized_and_drop`
`medium`	`56.68 ms` (➖ 1.03x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`9.51 ns` (➖ 1.01x faster)	`9.51 ns` (➖ 1.00x faster)	`9.61 ns` (➖ 1.00x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`85.47 µs` (➖ 1.01x slower)

virtq_readonly

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`65536`	`2.23 µs` (➖ 1.01x faster)	`2.52 µs` (➖ 1.03x slower)
`262144`	`9.76 µs` (➖ 1.01x slower)	`10.04 µs` (➖ 1.00x faster)

virtq_readwrite

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`8192`	`1.27 µs` (➖ 1.05x slower)	`1.23 µs` (➖ 1.06x faster)
`65536`	`8.22 µs` (➖ 1.18x faster)	`8.29 µs` (➖ 1.16x faster)
`262144`	`36.38 µs` (➖ 1.03x faster)

mshv3 / intel (Linux) (➖ stable)

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`decode_vec_bytes_copy`	`encode_control`
	`832.73 µs` (➖ 1.11x slower)
`byte_chunks`		`890.43 ns` (➖ 1.01x slower)
`vec_bytes`		`642.85 ns` (➖ 1.08x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`262.59 ns` (➖ 1.01x faster)
`262144`	`656.12 ns` (➖ 1.01x faster)

sandboxes

	`create_initialized_and_drop`
`medium`	`66.83 ms` (➖ 1.04x slower)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`8.68 ns` (➖ 1.00x slower)	`9.44 ns` (➖ 1.08x slower)	`8.74 ns` (➖ 1.00x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`44.77 µs` (➖ 1.01x faster)

virtq_readonly

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`65536`	`2.29 µs` (➖ 1.02x faster)	`2.29 µs` (➖ 1.00x faster)
`262144`	`7.97 µs` (➖ 1.00x slower)	`8.02 µs` (➖ 1.01x slower)

virtq_readwrite

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`8192`	`889.31 ns` (➖ 1.02x faster)	`910.32 ns` (➖ 1.00x faster)
`65536`	`7.45 µs` (➖ 1.01x slower)	`7.46 µs` (➖ 1.00x faster)
`262144`	`40.07 µs` (➖ 1.09x faster)

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

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`decode_vec_bytes_copy`	`encode_control`
	`1.97 ms` (➖ 1.00x slower)
`byte_chunks`		`1.20 µs` (➖ 1.01x slower)
`vec_bytes`		`782.32 ns` (➖ 1.05x faster)

payload_allocation

	`slot_pool_segmented`
`65536`	`236.92 ns` (➖ 1.03x slower)
`262144`	`790.54 ns` (➖ 1.01x slower)

sandboxes

	`create_initialized_and_drop`
`medium`	`80.41 ms` (➖ 1.16x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`10.06 ns` (➖ 1.00x slower)	`10.00 ns` (➖ 1.00x slower)	`9.90 ns` (➖ 1.00x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`900.22 µs` (➖ 1.02x faster)

virtq_readonly

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`65536`	`2.35 µs` (➖ 1.08x faster)	`2.32 µs` (➖ 1.02x faster)
`262144`	`9.06 µs` (➖ 1.10x faster)	`8.87 µs` (➖ 1.04x faster)

virtq_readwrite

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`8192`	`1.28 µs` (➖ 1.01x faster)	`1.30 µs` (➖ 1.02x slower)
`65536`	`8.91 µs` (➖ 1.05x faster)	`9.25 µs` (➖ 1.02x slower)
`262144`	`38.36 µs` (➖ 1.13x faster)

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

No benchmark improved or regressed.

Benchmark Results

function_call_codec

	`decode_vec_bytes_copy`	`encode_control`
	`2.90 ms` (➖ 1.03x faster)
`byte_chunks`		`1.18 µs` (➖ 1.00x faster)
`vec_bytes`		`787.64 ns` (➖ 1.02x slower)

payload_allocation

	`slot_pool_segmented`
`65536`	`207.86 ns` (➖ 1.01x faster)
`262144`	`760.93 ns` (➖ 1.03x slower)

sandboxes

	`create_initialized_and_drop`
`medium`	`104.97 ms` (➖ 1.01x faster)

slot_pool

	`alloc_dealloc_4096`	`alloc_dealloc_128`	`alloc_dealloc_1500`
	`10.06 ns` (➖ 1.00x slower)	`9.92 ns` (➖ 1.03x slower)	`9.80 ns` (➖ 1.02x slower)

snapshot_files

	`load_snapshot_unverified`
`small`	`625.35 µs` (➖ 1.22x slower)

virtq_readonly

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`65536`	`2.58 µs` (➖ 1.10x slower)	`2.30 µs` (➖ 1.00x slower)
`262144`	`7.76 µs` (➖ 1.02x slower)	`7.77 µs` (➖ 1.03x slower)

virtq_readwrite

	`slot_pool_segmented`	`slot_pool_segmented_fragmented`
`8192`	`1.12 µs` (➖ 1.06x slower)	`1.26 µs` (➖ 1.17x slower)
`65536`	`8.26 µs` (➖ 1.18x faster)	`8.52 µs` (➖ 1.04x slower)
`262144`	`39.98 µs` (➖ 1.26x faster)

_{Reported by cargo ci bench-report --candidate run:40960542919 --config-file bench_report.toml.}

ludfjig added the kind/bugfix For PRs that fix bugs label Oct 29, 2026

Copilot AI balanced review requested due to automatic review settings October 29, 2026 21:46

ludfjig requested review from andreiltd, danbugs, dblnz, devigned, jprendes, jsturtevant, simongdavies, squillace and syntactically as code owners October 29, 2026 21:46

Copilot started reviewing on behalf of ludfjig October 29, 2026 21:49

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jsturtevant approved these changes Oct 29, 2026

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ludfjig merged commit a4563db into hyperlight-dev:main Oct 29, 2026
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hyperlight-gh-bot Bot commented Oct 29, 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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