[Fedora-xen] Not seeing all RAM

Itamar Reis Peixoto itamar at ispbrasil.com.br
Tue Jul 3 17:03:43 UTC 2007


with non xen kernel are you able to see all amount of memory ?

have you take a look on your bios to check if your video card is not using 
your memory ?


--------------------

Itamar Reis Peixoto

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----- Original Message ----- 
From: "Kanwar Ranbir Sandhu" <m3freak at thesandhufamily.ca>
To: "Daniel P. Berrange" <berrange at redhat.com>
Cc: <fedora-xen at redhat.com>
Sent: Tuesday, July 03, 2007 11:42 AM
Subject: Re: [Fedora-xen] Not seeing all RAM


> On Tue, 2007-07-03 at 15:23 +0100, Daniel P. Berrange wrote:
>> Let me guest - you are running a 32-bit kernel on the machine ? If so
>> the problem is likely that the BOIS is remapping a portion of memory
>> above the 4 GB mark, to make room for PCI device DMA zones. A 32-bit
>> kernel though can only access physical addrs upto 4 GB, so it can't
>> see the remapped memory.
>
> I'm aware of that, but in my case it doesn't make sense: the server only
> has 3 GB of RAM.  The kernel just doesn't see all of it.
>
> I was using kernel-xen-2.6.19-1.2895.fc6 and about 512 MB were missing.
> After upgrading to kernel-xen-2.6.20-1.2962.fc6, the kernel can see more
> memory, but I'm still missing about 256 MB.
>
> I'm going to open a new bug report for this.
>
>> PCI device mapping to DomUs is insanely fragile, whether it works or not
>> is mostly luck. In this case since you added more memory, the locaiton of
>> the PCI device's DMA zone probably changed and by (bad) luck is no longer
>> accessible to the DomU or something like that.
>
> That's what I figured, though I don't know all of the details.  However,
> with the new kernel being able to see more of the 3 GB, the domU is
> working again.  The pci device I'm hiding from dom0 is being properly
> handed to the domU.
>
> Regards,
>
> Ranbir
> -- 
> Kanwar Ranbir Sandhu
> Linux 2.6.20-1.2944.fc6 i686 GNU/Linux
> 10:42:35 up 20:50, 2 users, load average: 2.15, 2.16, 1.45
>
>
> --
> Fedora-xen mailing list
> Fedora-xen at redhat.com
> https://www.redhat.com/mailman/listinfo/fedora-xen
> 




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