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

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Aug 23, 2012 at 09:28:31AM +0100, Jonathan Tripathy wrote:
> 
> 
> On 23.08.2012 09:12, Keir Fraser wrote:
> >On 23/08/2012 08:27, "Jonathan Tripathy" <jonnyt@xxxxxxxxxxx> wrote:
> >
> >>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-sho
> >>uld-be-8gb-uefi-boot),
> >>would have have any bad consequences? I'm very security
> >>conscience as
> >>the DomUs are untrusted...
> >
> >Firstly, the same effect *should* be had by adding no-real-mode to
> >your Xen
> >command line. So try that first.
> >
> >Secondly, it is arguable that we should patch Xen to prefer
> >"Multiboot-e820"
> >over "Xen-e801".
> >
> >And yes, overall if you have a UEFI BIOS then using UEFI Xen is
> >probably
> >best of all :)
> >
> 
> Unfortunately, no-real-mode didn't work :(
> 
> In xm info, I see
> 
> xen_commandline : placeholder no-real-mode
> 
> Not sure where placeholder is coming from...
> 

"placeholder" is usually added by grub in Debian/Ubuntu,
to overcome a bug/issue with multiboot and (old versions of) Xen.. 

(so in some old Xen versions with grub2 multiboot the first cmdline parameter 
got lost, but that hasn't really been the case for a long time anymore,
so placeholder is not needed these days.)


-- Pasi


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