When you upgrade your motherboard firmware (such as the BIOS or UEFI), you have to reboot your system. Thanks to a new patch from Intel, both BIOS and UEFI updates can be done without forcing a reboot.
How is this possible? Currently, an upgrade is done by uploading the firmware from within the operating system. The desktop or server is then rebooted, at which point the firmware is transferred to the motherboard and is flashed to either the BIOS or UEFI. However, there’s a new API specification, called Platform Firmware Runtime Update and Telemetry (PFRUT), which makes it possible to flash the firmware without the reboot. Intel has been working on PFRUT (previously dubbed Seamless Update) for quite a while now, in order to reduce downtime for servers. The idea is to enable such machines to reach that mythical 100% uptime.
The new driver, pfr_update, will be introduced in the Linux kernel 5.17 and is designed primarily for system firmware updates to patch critical bugs and security issues. This would make it possible for admins to patch firmware for critical issues, without having to suffer downtime.
One of the biggest surprises to come along with PFRUT, is that it will only be available for Linux (so Windows users need not apply).
You can read about the patch in this Kernel.org entry.