"UEFI firmware, Xen not detecting e820 map"

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"UEFI firmware, Xen not detecting e820 map"

Yaqub Alwan
Hi all,

I was in the ##xen freenode channel seeking help for an issue with memory being unrecognised above 512mb, and iommu not being detected using xen 4.1.2. The guys there determined that xen was not recognising my system e820 map and using only the e801 map, and recommended I emailed the details to this list. I appreciate that this list is not for technical queries, so I do not expect any help, but write this to enable xen developers to troubleshoot the issue for future patches.

My system is a Supermicro X9SCV-Q with 16GB of installed memory and a 2720QM CPU. The motherboard, as far as I am aware, only supports EFI booting (I have a query with the manufacturer to find out if it supports legacy boot).
Xen hypervisor only detects 511MB memory, but If I boot the regular linux kernel, I get the full 16GB.

Please find the output from xm dmesg here: http://pastebin.com/a1LC2csr

Please find the output from normal linux boot dmesg here: http://pastebin.com/CjePrLkx

You can see that native Linux kernel is finding the e820 memory map, but xen only sees e801 map.

Please let me know if you would require more information, I shall do my best to assist.

Kind regards,

Yaqub

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Re: "UEFI firmware, Xen not detecting e820 map"

Jan Beulich-2
>>> On 06.05.12 at 17:11, Yaqub Alwan <[hidden email]> wrote:
> I was in the ##xen freenode channel seeking help for an issue with memory
> being unrecognised above 512mb, and iommu not being detected using xen
> 4.1.2. The guys there determined that xen was not recognising my system
> e820 map and using only the e801 map, and recommended I emailed the details
> to this list. I appreciate that this list is not for technical queries, so
> I do not expect any help, but write this to enable xen developers to
> troubleshoot the issue for future patches.
>
> My system is a Supermicro X9SCV-Q with 16GB of installed memory and a
> 2720QM CPU. The motherboard, as far as I am aware, only supports EFI
> booting (I have a query with the manufacturer to find out if it supports
> legacy boot).
> Xen hypervisor only detects 511MB memory, but If I boot the regular linux
> kernel, I get the full 16GB.
>
> Please find the output from xm dmesg here: http://pastebin.com/a1LC2csr 
>
> Please find the output from normal linux boot dmesg here:
> http://pastebin.com/CjePrLkx 
>
> You can see that native Linux kernel is finding the e820 memory map, but
> xen only sees e801 map.

The Linux boot you looked at is an EFI one, so in order to do a proper
comparison you should look at Xen booting from EFI too, without any
intermediate boot loader involved (which requires that you use -unstable
or a 4.1.x code base that backports the native EFI boot support, e.g.
SLE11 SP2).

Jan


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