Fix guest tracing filter by dblnz · Pull Request #977 · hyperlight-dev/hyperlight

dblnz · 2025-10-24T15:02:41Z

This closes #990.
Currently, when tracing guests, the max log level parameter provided to the guest is not used to filter out traces.

This PR adds the filtering capability for the guest tracing and also modifies some of the trace levels in the guest.
For that to work, a change in the integration_tests.rs was necessary to update the number of expected logs in log_message test

ludfjig

LGTM, but it would be nice if it was possible to remove all uses of tracing::log::LeverFilter and log::Levelfilter for tracing_core::LevelFilter/tracing::LevelFilter instead

ludfjig · 2026-01-23T18:25:08Z

src/hyperlight_guest_tracing/src/subscriber.rs

+fn convert_level_filter(filter: tracing::log::LevelFilter) -> tracing_core::LevelFilter {
+    match filter {
+        tracing::log::LevelFilter::Off => tracing_core::LevelFilter::OFF,
+        tracing::log::LevelFilter::Error => tracing_core::LevelFilter::ERROR,
+        tracing::log::LevelFilter::Warn => tracing_core::LevelFilter::WARN,
+        tracing::log::LevelFilter::Info => tracing_core::LevelFilter::INFO,
+        tracing::log::LevelFilter::Debug => tracing_core::LevelFilter::DEBUG,
+        tracing::log::LevelFilter::Trace => tracing_core::LevelFilter::TRACE,
+    }


Is it possible to tracing_core::LevelFilter everywhere instead of having this? (in entrypoint of hyperlight_guest_bin + whatever the host passes to the guest)?

I think it is doable, I just wanted to avoid breaking changes.
But I think we'll have breaking changes this release anyway

It turns out it's more complicated that I had anticipated.
First of all, tracing_core::LevelFIlter cannot be cast to u64 as an entrypoint argument. So, we still need to do some conversions.
Secondly, the logger inside the guest, still needs a log::LevelFilter.

The solution I've used is to have a separate hyperlight_common::log_level::GuestLogFilter that can convert from/to u64 and from/to LevelFilter (both log/tracing ones).

I think this is a short term solution, because I am going to eliminate the logger inside the guest, to only use the tracing approach across the guests logs and traces. That will eliminate the need for log::LevelFilter.

Let me know your opinion on this.

jsturtevant · 2026-02-18T17:55:54Z

@dblnz would you like to get this into the next release (we have it scheduled for next week (Feb 25th)

dblnz · 2026-02-18T19:31:30Z

@dblnz would you like to get this into the next release (we have it scheduled for next week (Feb 25th)

Yes, I'm rebasing it to include it in the release

…arent Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

… and logging Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

ludfjig · 2026-02-20T18:15:59Z

src/tests/rust_guests/simpleguest/src/main.rs

+    let level =
+        LevelFilter::from(GuestLogFilter::try_from(level as u64).expect("Invalid log level"));
    let level = LevelFilter::iter().nth(level as usize).unwrap().to_level();


should we remove the second level?

ludfjig · 2026-02-20T18:16:59Z

src/hyperlight_host/src/hypervisor/hyperlight_vm.rs

 #[cfg(crashdump)]
 use crate::sandbox::uninitialized::SandboxRuntimeConfig;

+/// Get the logging level filter to pass to the guest entrypoint


not sure whether I agree that this should go in this file but it's not a blocker

ludfjig · 2026-02-20T18:18:20Z

src/hyperlight_guest_tracing/Cargo.toml

 [dependencies]
 hyperlight-common = { workspace = true, default-features = false }
 spin = "0.10.0"
-tracing = { version = "0.1.44", default-features = false, features = ["attributes"] }


did you mean to include this added feature log? https://docs.rs/tracing/latest/tracing/#emitting-log-records. I thought we wanted to switch to tracing

Copilot

Pull request overview

This PR fixes issue #990 by implementing proper filtering of guest tracing spans and events based on the max_log_level parameter. Previously, even though the log level was correctly received by guests, only logs were filtered while tracing spans and events were not.

Changes:

Introduced a new GuestLogFilter enum to unify log level conversions between log::LevelFilter, tracing_core::LevelFilter, and u64 values passed across the host-guest boundary
Implemented filtering in the GuestSubscriber::enabled() method to properly filter tracing spans and events based on the maximum log level
Updated trace span levels from Trace to Info for infrastructure calls (halt, dispatch_function, call_guest_function, call_host_function) to ensure they are visible at appropriate log levels and updated test expectations accordingly

Reviewed changes

Copilot reviewed 18 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/hyperlight_common/src/log_level.rs	New file introducing GuestLogFilter enum with conversions to/from log::LevelFilter, tracing_core::LevelFilter, and u64
src/hyperlight_common/src/lib.rs	Adds log_level module export
src/hyperlight_common/Cargo.toml	Adds tracing-core dependency
src/hyperlight_guest_tracing/src/subscriber.rs	Adds max_log_level field and implements filtering in enabled() method
src/hyperlight_guest_tracing/src/lib.rs	Updates init_guest_tracing to accept LevelFilter parameter
src/hyperlight_guest_tracing/Cargo.toml	Adds "log" feature to tracing dependency for log/tracing interop
src/hyperlight_guest_bin/src/lib.rs	Updates to use GuestLogFilter for initialization
src/hyperlight_guest_bin/src/guest_logger.rs	Minor parameter rename for clarity
src/hyperlight_guest_bin/src/guest_function/call.rs	Updates trace levels from Trace to Info and removes explicit parent span references
src/hyperlight_host/src/hypervisor/mod.rs	Removes old get_max_log_level function
src/hyperlight_host/src/hypervisor/hyperlight_vm.rs	Adds new get_max_log_level_filter and get_guest_log_filter functions with proper conversions
src/hyperlight_host/src/sandbox/uninitialized.rs	Updates imports to use tracing_core::LevelFilter
src/hyperlight_host/src/sandbox/trace/context.rs	Updates span levels from trace to info
src/hyperlight_host/tests/integration_test.rs	Updates test expectations to account for new info-level trace logs and converts to use tracing_core::LevelFilter
src/hyperlight_guest/src/exit.rs	Updates halt span level from Trace to Info
src/hyperlight_guest/src/guest_handle/io.rs	Removes explicit parent span reference
src/hyperlight_guest/src/guest_handle/host_comm.rs	Adds instrumentation and updates trace levels
src/tests/rust_guests/simpleguest/src/main.rs	CRITICAL BUG: Incorrect conversion logic in LogMessage function
Cargo.lock files	Updates dependency locks for tracing-core additions

Copilot · 2026-02-20T18:19:44Z

src/tests/rust_guests/simpleguest/src/main.rs

+    let level =
+        LevelFilter::from(GuestLogFilter::try_from(level as u64).expect("Invalid log level"));
    let level = LevelFilter::iter().nth(level as usize).unwrap().to_level();


The conversion logic on lines 466-468 is incorrect. Line 466-467 converts the input level (i32) to a log::LevelFilter, but then line 468 attempts to use that LevelFilter as a usize index with .nth(level as usize), which is a type error since LevelFilter is an enum that cannot be directly cast to usize.

The correct approach is to call .to_level() directly on the LevelFilter obtained from line 467, without the intermediate .iter().nth() step. The corrected code should be:

let filter = LevelFilter::from(GuestLogFilter::try_from(level as u64).expect("Invalid log level")); let level = filter.to_level();

Suggested change

let level =

LevelFilter::from(GuestLogFilter::try_from(level as u64).expect("Invalid log level"));

let level = LevelFilter::iter().nth(level as usize).unwrap().to_level();

let filter =

LevelFilter::from(GuestLogFilter::try_from(level as u64).expect("Invalid log level"));

let level = filter.to_level();

Copilot · 2026-02-20T18:19:45Z

src/hyperlight_common/src/log_level.rs

+            GuestLogFilter::Trace => 5,
+        }
+    }
+}


Consider adding unit tests for the GuestLogFilter conversions to ensure bidirectional conversion correctness between u64, GuestLogFilter, log::LevelFilter, and tracing_core::LevelFilter. This would help prevent regressions if the underlying crate enums change their discriminant values.

Suggested change

}

}

#[cfg(test)]

mod tests {

use super::GuestLogFilter;

#[test]

fn guest_log_filter_u64_roundtrip() {

let variants = [

GuestLogFilter::Off,

GuestLogFilter::Error,

GuestLogFilter::Warn,

GuestLogFilter::Info,

GuestLogFilter::Debug,

GuestLogFilter::Trace,

];

for variant in variants {

let as_u64: u64 = variant.into();

let back = GuestLogFilter::try_from(as_u64).expect("conversion from u64 should succeed");

assert_eq!(variant, back);

}

}

#[test]

fn guest_log_filter_tracing_roundtrip() {

let variants = [

GuestLogFilter::Off,

GuestLogFilter::Error,

GuestLogFilter::Warn,

GuestLogFilter::Info,

GuestLogFilter::Debug,

GuestLogFilter::Trace,

];

for variant in variants {

let tracing_filter: tracing_core::LevelFilter = variant.into();

let back: GuestLogFilter = tracing_filter.into();

assert_eq!(variant, back);

}

}

#[test]

fn guest_log_filter_try_from_u64_rejects_invalid() {

// Any value outside the defined range [0, 5] should be rejected.

assert!(GuestLogFilter::try_from(u64::MAX).is_err());

assert!(GuestLogFilter::try_from(6).is_err());

}

}

dblnz added the kind/enhancement For PRs adding features, improving functionality, docs, tests, etc. label Oct 24, 2025

dblnz self-assigned this Oct 24, 2025

dblnz force-pushed the fix-tracing-filter branch from 489acde to 7ff7b03 Compare October 24, 2025 15:19

dblnz force-pushed the fix-tracing-filter branch from 7ff7b03 to 58caf0d Compare January 23, 2026 12:30

dblnz marked this pull request as ready for review January 23, 2026 12:31

dblnz requested review from danbugs, devigned, jprendes, ludfjig, marosset, simongdavies and syntactically as code owners January 23, 2026 12:31

ludfjig previously approved these changes Jan 23, 2026

View reviewed changes

dblnz dismissed ludfjig’s stale review via 3f6bb07 February 18, 2026 19:19

dblnz force-pushed the fix-tracing-filter branch from 58caf0d to 3f6bb07 Compare February 18, 2026 19:19

dblnz added 2 commits February 19, 2026 09:58

[trace-guest] Update guest library trace levels and remove explicit p…

df00edf

…arent Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

[trace-guest] Add trace/events filtering based on max_log_level

887d003

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

dblnz force-pushed the fix-tracing-filter branch 4 times, most recently from 4fc6b1c to 6e47f8f Compare February 19, 2026 11:19

[trace-guest] Define a common log level filter to be used for tracing…

72aaf11

… and logging Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

dblnz force-pushed the fix-tracing-filter branch from 6e47f8f to 72aaf11 Compare February 19, 2026 14:13

jsturtevant approved these changes Feb 20, 2026

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ludfjig requested a review from Copilot February 20, 2026 18:14

Copilot started reviewing on behalf of ludfjig February 20, 2026 18:14 View session

ludfjig approved these changes Feb 20, 2026

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Copilot AI reviewed Feb 20, 2026

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Fix guest tracing filter#977

Fix guest tracing filter#977
dblnz wants to merge 3 commits intohyperlight-dev:mainfrom
dblnz:fix-tracing-filter

dblnz commented Oct 24, 2025 •

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-}
+}
+#[cfg(test)]
+mod tests {
+    use super::GuestLogFilter;
+    #[test]
+    fn guest_log_filter_u64_roundtrip() {
+        let variants = [
+            GuestLogFilter::Off,
+            GuestLogFilter::Error,
+            GuestLogFilter::Warn,
+            GuestLogFilter::Info,
+            GuestLogFilter::Debug,
+            GuestLogFilter::Trace,
+        ];
+        for variant in variants {
+            let as_u64: u64 = variant.into();
+            let back = GuestLogFilter::try_from(as_u64).expect("conversion from u64 should succeed");
+            assert_eq!(variant, back);
+        }
+    }
+    #[test]
+    fn guest_log_filter_tracing_roundtrip() {
+        let variants = [
+            GuestLogFilter::Off,
+            GuestLogFilter::Error,
+            GuestLogFilter::Warn,
+            GuestLogFilter::Info,
+            GuestLogFilter::Debug,
+            GuestLogFilter::Trace,
+        ];
+        for variant in variants {
+            let tracing_filter: tracing_core::LevelFilter = variant.into();
+            let back: GuestLogFilter = tracing_filter.into();
+            assert_eq!(variant, back);
+        }
+    }
+    #[test]
+    fn guest_log_filter_try_from_u64_rejects_invalid() {
+        // Any value outside the defined range [0, 5] should be rejected.
+        assert!(GuestLogFilter::try_from(u64::MAX).is_err());
+        assert!(GuestLogFilter::try_from(6).is_err());
+    }
+}

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dblnz commented Oct 24, 2025 •

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