[TUHS] kernel boots kernel in 1977

[Bakul Shah via TUHS]

> On Sep 19, 2024, at 5:20 PM, Steffen Nurpmeso <steffen at sdaoden.eu> wrote:
> 
> Bakul Shah via TUHS wrote in
> <3B4CF41C-3D88-471D-B5E7-6F06C772F5E7 at iitbombay.org>:
> |Forget "rings". Unix needs only two states from hardware.
> |Forget virtualization for now as well.
> |
> |The kernel runs in the supervisor state, the user code in the
> |unprivileged state where it can't execute or see certain
> |instructions or processor state or peripherals and must make
> |system calls for controlled access to the same.
> |
> |In addition Unix has the "root" user that can access much more
> |but it too must go through the system call interface.
> |
> |A "warm reboot" system call would simply arrange things so that
> |the new kernel image is copied in the right place and control
> |will eventually pass to it.
> |
> |It is not so simple these days as the hardware is much more
> |complex and often requires vendor provided firmware assist
> |to properly initialize the system before control gets passed
> |to an OS kernel but no change in the protection model is
> |required for a kernel to kernel handoff.
> 
> It seems to me it is worse.  The Linux driver of my WLAN chip
> would (i have forgotten the condition, but anyhow) leave the chip
> in some false state, and it could not be overcome except by
> booting into the (minimzed as much as possible: 31.4G) by-default
> installed Windows, up to the login screen, by then it would have
> been fixed.  This was with the RTW88 driver, it was ok iirc in
> 4.19, which had another one.  Somewhere i have found someone
> saying one has to pass an argument, i asked for documentation
> i think even via bugzilla, but nothing ever happened.  But it
> worked (and the driver became better, and i think firmware also,
> both "a bit"), and now it is luckily stable again for some years.
> I do not know whether the flag is still needed...
> 
>  KEXEC_ARGS="--append=\"rtw88_pci.disable_aspm=1 rc.hostname=kent\""

I don't see how "it is worse".