Re: Can't see more than 3.5GB of RAM / UEFI / no e820 memory map detected

[Jonathan Tripathy <jonnyt@abpni.co.uk>]

On 23/08/2012 08:22, Pasi Kärkkäinen wrote:
> On Thu, Aug 23, 2012 at 09:06:20AM +0300, Pasi Kärkkäinen wrote:
>> On Thu, Aug 23, 2012 at 12:48:01AM +0100, Jonathan Tripathy wrote:
>>> Hi Everyone,
>>>
>>> CC: Xen-users
>>>
>>> I am running Ubuntu 12.04 x86_64. My machine has a supermicro
>>> motherboard X9SCI-LN4F with 32GB of RAM installed. To get Xen, I simply
>>> did apt-get install xen-hypervisor which gives me Ubuntu's 4.1 xen version.
>>>
>>> For some reason, Xen can't see any more than about 3.5GB of RAM. I can
>>> confirm this by xentop as well as xm info. I am definately running a
>>> 64-bit Dom0 kernel as when I boot into it without Xen, I can see all
>>> 32GB of RAM by running "free -m".
>>>
>>> Has anybody come across this issue before? For what it's worth, I'm
>>> booting my system using UEFI - could that have something to do with it?
>>>
>>> Any help is very much appreciated
>>>
>> Yes, this is UEFI related issue. Can you turn UEFI off?
>>
>> It looks like you're not running UEFI capable Xen hypervisor.
>> (Xen 4.2 has UEFI support, and some vendors have backported UEFI support on older versions,
>> for example Suse SLES11SP2 contains UEFI support in Xen 4.1).
>>
> Fixed the line above :)
>                                       
> -- Pasi
>
Thanks, Pasi.

A couple of questions:

I'm guessing xen.efi (from 4.2) just replaces grub??

Also, if I were to apply that patch from superuser 
(http://serverfault.com/questions/342109/xen-only-sees-512mb-of-system-ram-should-be-8gb-uefi-boot), 
would have have any bad consequences? I'm very security conscience as 
the DomUs are untrusted...

Thanks