RE: [Xen-users] X86_64 and 4GB RAM

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: John Hannfield [mailto:hal9020@xxxxxxxxx] 
> Sent: 01 May 2007 11:53
> To: Petersson, Mats
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] X86_64 and 4GB RAM
> 
> Hi Mats
> 
> > What revision of processor do you have, and how large is 
> your graphics
> > memory?
> 
> The system has 2 dual core Opteron 2210's in it.

Ah, yes that is a Rev F, so it definitely allows memory hoisting. 


> cat /proc/cpuinfo
> 
> processor       : 0
> vendor_id       : AuthenticAMD
> cpu family      : 15
> model           : 65
[snip]
> 
> 
> > If you have a graphics card that eats a fair bit of memory (256 or
> > 512MB) on a processor that doesn't support "memory 
> hoisting"[1] (i.e.
> 
> It has an onboard graphics card, but I doubt it is high MB, as it is a
> dedicated server. A PenguinComputing Altus 1600

Yeah, onboard graphics usuall use around 16-32MB, so not a whole lot. 
> 
> > remapping of "behind PCI memory" to a higher address), then 
> I wouldn't
> > be surprised if you don't see more than 3.x GB - the reason 
> being that
> > the rest of the memory is "behind" the PCI bus devices.
> 
> > Also, if you have a newer processor you may need a new BIOS 
> to support
> > this, and you'll possibly also need to enable "memory hoisting" (or
> > memory hole or some such) in the BIOS setup.
> 
> My BIOS has options for
> 
> MemoryHole ReMapping     this is "Enabled"

That's the one we need... 

> MTRR Mapping                      this is  "Discrete"
> IOMMU Mode                         set to "256 MB"
> CS Sparing Enable               this is "Disabled"
> 
> The thing is it boots and shows all 4GB with a vanilla debian 
> etch bootup.
> It only has problems when booting in to Xen.

Hmm. Something is certainly going wrong here... 

--
Mats
> 
> -- 
> 
> John
> 
> 
> 



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