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Fix guest logging StackOverflow issue #1065
Description
What happened?
When using logging in a hyperlight guest that enables the use of tracing crate with the log or log-always feature, the guest returns StackOverflow.
This especially impacts hyperlight-wasm because it uses the log feature of tracing.
What did you expect to happen?
The expected behavior is for hyperlight to correctly receive the logs from the guest through the OutBAction::Log VMExit.
Steps to reproduce the behavior
- set
RUST_LOG="none,hyperlight_guest=trace,hyperlight_guest_bin=trace" - run a hyperlight guest example
- The guest returns
StackOverflow
Hyperlight Version
0.11.0
OS version
Details
On Linux:
$ cat /etc/os-release
PRETTY_NAME="Ubuntu 24.04.3 LTS"
NAME="Ubuntu"
VERSION_ID="24.04"
VERSION="24.04.3 LTS (Noble Numbat)"
VERSION_CODENAME=noble
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=noble
LOGO=ubuntu-logo
$ uname -a
Linux laptop 6.6.87.2-microsoft-standard-WSL2 #1 SMP PREEMPT_DYNAMIC Thu Jun 5 18:30:46 UTC 2025 x86_64 GNU/Linux
On Windows:
C:\> cmd /c ver
not tested but should behave the same
</details>
### Additional Information
When tracing is not enabled, the previous way of reporting logs, `outb` with `OutBAction::Log` action, calls [push_shared_output_data](https://github.com/hyperlight-dev/hyperlight/blob/main/src/hyperlight_guest/src/guest_handle/io.rs#L92) which is instrumented for logging/tracing. This `instrument` tries to send a new log again, this results in an infinite `loop` that produces the `StackOverflow`.
The reason for this issue is the `log_message` function call that reports the message to the host, more specifically the [hyperlight_guest/src/host_comm.rs#L196](https://github.com/hyperlight-dev/hyperlight/blob/main/src/hyperlight_guest/src/guest_handle/host_comm.rs#L196), that uses the `input/output` buffer for the log.
The simple solution is to remove the `instrument` from the `push_shared_output_data`, the correct solution is to use the same `event batching` logic and buffer as the tracing uses.
Activity
jsturtevant commentedon Feb 18, 2026
this is partially fixed in #1065