Re: [Xen-devel] Can't see more than 3.5GB of RAM / UEFI / no e820 memory map detected

[Jonathan Tripathy <jonnyt@xxxxxxxxxxx>]

On 24/08/2012 16:35, Jan Beulich wrote:
> > > > On 23.08.12 at 10:07, Jonathan Tripathy <jonnyt@xxxxxxxxxxx> wrote:
> > On 23.08.2012 08:39, Jan Beulich wrote:
> > > > > > Jonathan Tripathy <jonnyt@xxxxxxxxxxx> 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

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