[TUHS] kernel boots kernel in 1977

[Alan Coopersmith via TUHS]

On 9/19/24 00:13, Warner Losh wrote:
> Kexec does just this. The new kernel boots without going through the reset 
> vector. The old kernel keeps a tiny bit of code around that tears down all the 
> protections, etc and hands off to the new kernel a mostly reset machine.. but it 
> doesn't go through the firmware to do it... it was the original reason for it in 
> linux: fast reboot times.

Indeed - when Sun implemented the equivalent in Solaris, the feature was
literally named "Fast Reboot":

https://illumos.org/opensolaris/ARChive/PSARC/2008/382/final.materials/fastboot.txt

It will refuse to run and require a trip through the firmware if any active
drivers don't support or can't complete a "quiesce" routine to finish off
any in-progress operations and reset the the hardware to the state expected
for a fresh boot:

https://illumos.org/opensolaris/ARChive/PSARC/2008/382/final.materials/quiesce.man.txt

-- 
         -Alan Coopersmith-                 alan.coopersmith at oracle.com
          Oracle Solaris Engineering - https://blogs.oracle.com/solaris