Re: 2nd try: reboot hangs - a little more

[Miles Fidelman <mfidelman@meetinghouse.net>]

see end....

Miles Fidelman wrote:
> Ok...
> - booting with normal kernel... still doesn't reboot
> - booting with normal kernel, in single-user mode, with loglevel=7, 
> still doesn't work, with the following as the last few console messages:
>
> [36. ...] md: stopping all md devices
> [36. ...] md: md2 switched to read-only mode
> [38. ...] sd 0:0:1:0: [sdb: Synchronizing SCSI cache]
> [38. ...] sd 0:0:0:0: [sda: Synchronizing SCSI cache]
> [38. ...] ehci_hcd 0000:00:03.3 PCI INT D disabled
> [38. ...] ehci_hcd 0000:00:03.2 PCI INT C disabled
> [38. ...] ehci_hcd 0000:00:03.1 PCI INT B disabled
> [38. ...] ehci_hcd 0000:00:03.0 PCI INT A disabled
> [38. ...] Restarting system
> [38. ...] machine restart
>
> So.. it's not Xen, and the last console message is from the kernel, 
> just before it does <something> to jump to the restart code.
>
> This is the point at which you can use reboot=bios to tell an x86 
> kernel to jump to the BIOS' restart code, but you can't do that for an 
> amd64 kernel.
>
> Hmmm...... what next?  (I've tried pretty much all of the other reboot 
> options.)
So... a little perusing of kernal documentation and code (2.6.32-5), 
yields the observation that:

- in linux/arch/x86/kernel/reboot.c - there is code to support a kernal 
option "reboot=bios" that specifically writes, specific magic numbers, 
to several CMOS and memory locations, before jumping into the bios to 
restart -- this code ("machine_real_restart") is also used to deal with 
quirks of a long list of specific machines

- there is no equivalent code associated with the amd64 kernel (or 
anything besides the x86 kernel, for that matter)

I wonder why?  I wonder if there are any workarounds short of building a 
custom kernel?  I wonder who to ask?

Miles


--
In theory, there is no difference between theory and practice.
In practice, there is.   .... Yogi Berra