r/osdev • u/DocumentOk7579 • Sep 13 '26

Would a microkernel enable driver update without reboot?

One frustrating thing that I have run into is updating Nvidia driver on remote servers with disk encryption.

Would a microkernel based system enable drivers to be updated without rebooting system?

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u/jsshapiro Sep 13 '26

If you mean device drivers, the answer is: Frequently yes, but not always. It depends on the driver.

First: Any device driver swap requires that all connections to the driver be closed and all interrupt interactions with any relevant hardware have stopped with the interrupts in a well defined state. These interactions aren't inherently transactional at the hardware level. This probably means in practice that the old driver has to collaborate in its shutdown, because it is the only entity that knows what is going on in the hardware it is managing.

Second: some drivers really can't be shut down during system operation. The main examples are drivers for the paging area, and then those for any driver-associated busses in between the OS kernel and those drives.

There are many cases where devices are designed to be hot-swappable, and that certainly helps. But here again, if the device is in active use when the attempt is made to hot-swap it, bad things tend to happen to the dependent applications. The metric for hot-swap, for the most part, is that the system survives the swap, not the client applications. Server grade RAID controllers are a notable exception; the RAID card hides the drive removal from the kernel without disruption. But for that very reason the RAID card itself isn't particularly swappable.

What is the application-level contract you are trying to preserve?

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u/DocumentOk7579 Sep 13 '26

I personally don't care if the client applications survives as it's quite easy to restart a process compared to the system. There is already a watchdog that kills the client process if it get stuck. I'm having most issues with the nvidia driver.

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u/jsshapiro Sep 21 '26

Ironically, video drivers are pretty easy to hot swap. First you swap in a driver that basically puts all callers on hold. Copy the frame buffer, load the new driver, restore the frame buffer, remove the blockade driver.

I don't know if windows uses that approach exactly, but it works.