[Fedora-xen] Re: Heads-up: Requiring PAE for running Xen

[Daniel P. Berrange]

On Wed, May 17, 2006 at 11:42:43PM +0200, Axel Thimm wrote:
> On Wed, May 17, 2006 at 02:07:59PM -0400, Jeremy Katz wrote:
> > As we move forward with Xen enablement, there's a desire for
> > being able to access more than 4 gigs of RAM on 32-bit Xen hosts.  The
> > options for handling this are
> > 1) Another kernel.  This is bad due to 
> >    a) we're running out of CD space already
> >    b) keeping things matched up between the HV and the guest kernels
> >    c) migration is worlds of pain with two types of kernels
> > 2) Switch the 32-bit xen kernels to require PAE.  For most "current"
> > non-laptop hardware, this is a non-issue.  It does mean that xen won't
> > work a lot of earlier PentiumM laptops
> 
> How do I know if my laptop if affected? :)

Take a look at the 'flags' field in /proc/cpuinfo - look for a flag 
called 'pae' in it - if your CPU is a Pentium Mobile the chances are
you won't see the 'pae' flag there.

For example on my laptop which dosn't have PAE:

  [berrange at localhost ~]$ grep pae /proc/cpuinfo 
  [berrange at localhost ~]$ 

While on my desktop, which does have PAE:

  [berrange at camden berrange]$  grep pae /proc/cpuinfo 
  flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
  flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
  flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
  flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
  [berrange at camden berrange]$ 



Regards,
Dan.
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