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Maciej S. Szmigiero

PROFILE

Maciej S. Szmigiero

Worked on low-level virtualization and kernel development in C, focusing on reliability and observability improvements for the espressif/qemu and geerlingguy/linux repositories. Delivered targeted features such as new trace events to enhance migration lifecycle visibility and implemented bug fixes addressing RAM migration, VFIO device migration, and timekeeping stability during VM resets. Addressed interrupt delivery reliability in AVIC-enabled environments by ensuring proper TPR synchronization. Demonstrated a disciplined engineering approach with focused, auditable commits and clear documentation. Leveraged skills in debugging, tracing, and performance optimization to improve system programming workflows, resulting in more predictable virtualization performance and streamlined diagnostics for complex workloads.

Overall Statistics

Feature vs Bugs

40%Features

Repository Contributions

6Total
Bugs
3
Commits
6
Features
2
Lines of code
64
Activity Months4

Work History

August 2025

1 Commits

Aug 1, 2025

Aug 2025: Delivered a critical AVIC-related bug fix in geerlingguy/linux that ensures TPR synchronization from LAPIC to VMCB (V_TPR) remains intact even when AVIC is active, preventing interrupt delivery issues in guests and improving VM stability. The change is traceable to a single, well-documented commit for clear auditability and rollback planning.

December 2024

1 Commits

Dec 1, 2024

December 2024 monthly summary: Delivered a critical bug fix in espressif/qemu related to VM reset timekeeping. Implemented a fix to reset the TSCs of parked vCPUs during VM reset to restore sched_clock stability, addressing guest clock desynchronization. Impact: improved timekeeping reliability for virtualized workloads, reduced guest OS time drift, and fewer time-related failures. Approach: targeted i386 reset path changes and thorough validation across reset sequences. Business value: more predictable virtualization performance and easier debugging for time-sensitive applications. Technologies/skills demonstrated: QEMU/KVM internals, TSC and sched_clock concepts, i386 architecture, low-level C, and VM reset workflows.

November 2024

2 Commits • 1 Features

Nov 1, 2024

November 2024: Espressif/qemu VFIO Migration Observability Enhancements delivered to improve visibility and reliability of VFIO device migrations. Introduced tracing events to capture key lifecycle moments: start of each migration iteration, completion of the precopy phase, and signaling when no more data needs to be transferred for a device. Added a dedicated empty-hit trace for precopy blocks. These changes establish a foundation for dashboards, alerts, and faster diagnostics.

October 2024

2 Commits • 1 Features

Oct 1, 2024

October 2024 monthly summary for espressif/qemu focusing on migration subsystem improvements and reliability enhancements. Contributed two targeted changes in the QEMU migration module with measurable impact on observability, stability, and deployment confidence.

Activity

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Quality Metrics

Correctness96.6%
Maintainability93.4%
Architecture93.4%
Performance93.4%
AI Usage20.0%

Skills & Technologies

Programming Languages

C

Technical Skills

C programmingDebuggingKernel DevelopmentLow-level ProgrammingPerformance OptimizationSystem ProgrammingTracingVirtualizationkernel developmentvirtualization

Repositories Contributed To

2 repos

Overview of all repositories you've contributed to across your timeline

espressif/qemu

Oct 2024 Dec 2024
3 Months active

Languages Used

C

Technical Skills

DebuggingKernel DevelopmentLow-level ProgrammingSystem ProgrammingTracingVirtualization

geerlingguy/linux

Aug 2025 Aug 2025
1 Month active

Languages Used

C

Technical Skills

C programmingkernel developmentvirtualization