Re: Running Mezzano in bhyve

> Hi! Mezzano is an operating system written in Common lisp. I would like 
> to test it in bhyve. When I launch it, it spins infinitely in a loop 
> measuring how many CPU cycles it makes in a unit of time (I understood 
> it by adding various debug messages).
> 
> The timer it uses is something called a PIT: 
> https://wiki.osdev.org/Programmable_Interval_Timer 
> <https://wiki.osdev.org/Programmable_Interval_Timer>
> 
> The problem is, once the timer is configured it fires an interrupt only 
> once, while it obviously must fire interrupts constantly at some 
> frequency (100 Hz, as I understand from the code).
> 
> Is the PIT supported by bhyve? Does FreeBSD use it anywhere in its kernel?

  Yes, though mode 3 of the timer isn't supported by the device 
emulation. It appears that Mezzano uses that mode
 
https://github.com/froggey/Mezzano/blob/master/supervisor/x86-64/time.lisp#L20

  Try this patch to the PIT code to see if it helps
     https://people.freebsd.org/~grehan/bhyve_vatpit.diff

later,

Peter.