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Re: Call for Debian Installer testing, before D-I Beta1 release

On Wed, Feb 20, 2008 at 11:07:03AM +0100, Frans Pop wrote:
> On Wednesday 20 February 2008, Grant Grundler wrote:
> > > Please, go in your installed system and use the installation-report
> > > script to send us a full installation report, that way we can get more
> > > information about how things went there.
> >
> > I'm not near the system for the next couple of days but will do that
> > when I get back - thanks for pointing that out.
> That's not really needed anymore as I've already made the necessary changes 
> to detect smp support. They will only be uploaded after the Beta1 release 
> though.
> See also my replies to your original mail (not CCed).

ok - cool

> Grant, do you happen to know a similar trick to detect 64-bit support even 
> when the installer is running with a 32-bit kernel?

Hrm...yes. I explain the "trick" and also some caveats on why I would
rather leave this user selectable.

grundler@gsyprf11:~$ fgrep "PA-RISC 2.0" /proc/cpuinfo 
cpu family      : PA-RISC 2.0
cpu family      : PA-RISC 2.0

Anything with PA 2.0 CPU can run 64-bit.

In general, we want to run 32-bit kernel because:
o PA-RISC to date _only_ has a 32-bit usr space. So all syscalls to
  a 64-bit kernel go through a "wrapper" to convert 32-bit user space
  arguments to 64-bit kernel calling conventions. 
  (some work is being done to enable 64-bit user space but it's not
   ready yet).
o pointers are smaller and thus data structures are more compact.
  Simple applications are _slower_ with 64-bit.

We must/can run 64-bit IFF:
o PAT PDC (aka BIOS) - palo boot loader detects PAT PDC and will
  attempt to boot a 64-bit kernel. No changes needed for this.

o chunks of physical memory are mapped above 4GB.
  Different platforms will have different physical memory maps.
  /proc/meminfo is of no help here.
  But /proc/iomem might be helpful:
	grundler@gsyprf11:~$ fgrep "System RAM" /proc/iomem
	00000000-efffffff : System RAM
	100000000-1ffffffff : System RAM
	10f0000000-10ffffffff : System RAM

  These are the physical addresses of RAM for an "A500" (aka rp2470)
  with 8GB of RAM:
	grundler@gsyprf11:~$ cat /proc/meminfo 
	MemTotal:      8239436 kB
	MemFree:        414672 kB
	Buffers:       1812020 kB
	Cached:        4587320 kB
	SwapCached:         72 kB
	Active:        4434600 kB
	Inactive:      2115708 kB

  This is really only a problem for "Astro" (e.g. C3000) chipset workstations.
  They have PA2.0 CPUs and can have physical RAM above 4GB address.

> Currently the installer will only select a 64-bit kernel if the user changed 
> to the 64-bit D-I kernel when the installer was booted (which can be done 
> by answering Yes to the question asked by the firmware whether you want to 
> interact with the boot loader).

Unless someone wants to code up the above rules, my preference would be
to leave this up to the user. We can revisit this issue when 64-bit user
space is working.


> Cheers,

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