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

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

On 24/08/2012 16:35, Jan Beulich wrote:
>>>> On 23.08.12 at 10:07, Jonathan Tripathy <jonnyt@abpni.co.uk> wrote:
>> On 23.08.2012 08:39, Jan Beulich wrote:
>>>>>> Jonathan Tripathy <jonnyt@abpni.co.uk> 08/23/12 9:29 AM >>>
>>>> I'm guessing xen.efi (from 4.2) just replaces grub??
>>> "Replaces" is the wrong term. It simply makes the use of grub.efi (or
>>> however
>>> it's named) unnecessary.
>>>
>>>> Also, if I were to apply that patch from superuser
>>>> (http://serverfault.com/questions/342109/xen-only-sees-512mb-of-system-ram-sh
>> ould-be-8gb-uefi-boot),
>>>> would have have any bad consequences? I'm very security conscience as
>>>> the DomUs are untrusted...
>>> If you wanted to do that, I'd strongly recommend only removing the
>>> E801 code
>>> (obviously, from your log, you don't get E820 entries reported
>>> anyway, so this
>>> would be to not harm using hypervisors built from the same source on
>>> other
>>> systems) or simply swapping the E801 and multiboot handling order
>>> (which may
>>> actually be something to consider even upstream, so you'd be welcome
>>> to post
>>> such a patch).
>>>
>>> But in the end, in order to indeed use UEFI as intended, you'll need
>>> to switch to
>>> using xen.efi and an EFI-enabled Dom0 kernel (which upstream pv-ops
>>> for now
>>> isn't).
>> I'll submit a patch with the map entries in the if block swapped. I'll
>> make the patch, then test it for you guys, then post it. Do I just send
>> it to this list (for the benefit of others and for upstream
>> consideration)?
> Yes.
>
>> When you say "use UEFI as intended", is there something wrong with just
>> flipping the if block on its head?
> That flipping has nothing to do with UEFI, just with the way grub.efi
> works.
>
> Proper UEFI support implies use of EFI's boot and run time services,
> which only xen.efi currently does (and which, for those run time
> services that get made available for use by Dom0, also requires an
> enabled Dom0 kernel).
>
Thanks for the clarification.

So from a security/reliability standpoint, nothing will be affected by 
flipping the if block?

Sorry that I haven't submitted the patch yet, just been very busy. This 
is on my to-do list this weekend.

Thanks