Stefan Hajnoczi

This is the fourth post in a series about building a virtio-serial device in Verilog for an FPGA development board.

This is the final post in a series about building a virtio-serial device in Verilog for an FPGA development board.

This is the fifth post in a series about building a virtio-serial device in Verilog for an FPGA development board.

This is the third post in a series about building a virtio-serial device in Verilog for an FPGA development board.

This is the second post in a series about building a virtio-serial device in Verilog for an FPGA development board.

This is a the first post in a series about building a virtio-serial device in Verilog for a Field Programmable Gate Array (FPGA) development board.

With the VIRTIO 1.4 specification for I/O devices expected to be published soon, here are the most prominent changes.

My KVM Forum 2025 talk "Making io_uring Pervasive in QEMU" is now available on YouTube.

A fair amount of the development work I do is related to storage performance in QEMU/KVM.

My KVM Forum 2024 talk "IOThread Virtqueue Mapping: Improving virtio-blk SMP scalability in QEMU" is now available on YouTube.

Programming languages currently offer few defences against supply chain attacks where a malicious third-party library compromises a program.

KubeVirt makes it possible to run virtual machines on Kubernetes alongside container workloads.

File systems and relational databases are like cousins.

This post is about the AioContext lock removal in QEMU 9.0 (planned for release in 2024), how we got here, and what it means for multi-threaded code in QEMU.

I recently looked at papers about free space management and snapshots in storage systems like file systems, volume managers, and key-value stores.

Update: The video is now available here and the slides are available here (PDF).

I hacked up a prototype multi-player game in just a static HTML/JS files.

The 1.3.0 release of the libblkio high-performance block device I/O library is out. libblkio provides an API that abstracts various storage interfaces that are efficient but costly to integrate into applications including io_uring, NVMe uring_cmd, virtio-…

Every once in a while a bug comes along where a guest hangs while communicating with a QEMU VIRTIO device.

I started working on libblkio in 2020 with the goal of creating a high-performance block I/O library.

At FOSDEM '23 I gave a talk about vhost-user-blk and its use as a userspace block I/O interface.

vhost-user-blk has connected hypervisors to software-defined storage since around 2017, but it was mainly seen as virtualization technology.

At KVM Forum 2022 Kevin Wolf and Stefano Garzarella gave a talk on qemu-storage-daemon, a way to get QEMU's storage functionality without running a VM.

vhost-user-blk is a high-performance storage protocol that connects virtual machines to software-defined storage like SPDK or qemu-storage-daemon.

Queues and their implementation using shared memory ring buffers are a standard tool for communicating with I/O devices and between CPUs.