KVM Forum 2019

virtio-fs is a new shared file system for virtual machines. Unlike previous approaches, it is designed to take advantage of the co-location of virtual machines and the hypervisor to achieve local file system semantics and performance. This talk covers the status of virtio-fs, its key features, and use cases.

Amongst its features, the ability to share the host page cache with the guest is unique and not available in other shared file systems. This leads to interesting applications, including local file system mmap MAP_SHARED semantics, memory footprint reduction, and efficient page cache sharing between guests.

This talk also covers metadata coherence and the shared memory version table that is being developed to achieve this. The table allows guests accessing the same files and directories to have a consistent view even when other guests make changes to the file system.