Pkg xen devel - Jan 2009 - i386 hypervisor seeing only ~16G RAM, amd64 required?

Hi,

I have several machines using xen-hypervisor-3.2-1-i386 from
etch-backports and they recently got upgraded to 20 or 24G RAM.  I
have seen talk of a limit of a 16G RAM with 32bit PAE Xen and indeed
this is what I am seeing.

I am guessing there is still no way to get the 32bit hypervisor to
see more than 16G RAM, and I must go to 64bit.

Can I boot a 64bit hypervisor and still keep the same 32bit dom0?
What're people's experiences running 32bit domUs on
xen-hypervisor-3.2-1-amd64?

Cheers,
Andy
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On Thu, 2009-01-15 at 00:46 +0000, Andy Smith wrote:
> Hi,
> 
> I have several machines using xen-hypervisor-3.2-1-i386 from
> etch-backports and they recently got upgraded to 20 or 24G RAM.  I
> have seen talk of a limit of a 16G RAM with 32bit PAE Xen and indeed
> this is what I am seeing.
> 
> I am guessing there is still no way to get the 32bit hypervisor to
> see more than 16G RAM, and I must go to 64bit.
Correct, PAE hypervisor can only use 16G of RAM.
> Can I boot a 64bit hypervisor and still keep the same 32bit dom0?
> What're people's experiences running 32bit domUs on
> xen-hypervisor-3.2-1-amd64?
Yes, a 64 bit hypervisor can run both 32 and 64 bit guests, including
dom0, mixed and matched as you like. I run a 32on64 dom0 all the time.

I think you will need a dom0 kernel more recent than the one in Etch to
support guests of a different width to dom0, I'm not sure when exactly
this support was added but Lenny's kernel is certainly OK.

Ian.
-- 
Ian Campbell

BOFH excuse #1:

clock speed
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On Thu, Jan 15, 2009 at 12:46:43AM +0000, Andy Smith
wrote:
> I have several machines using xen-hypervisor-3.2-1-i386 from
> etch-backports
This version is not supported by anyone. Use the version from Lenny.
> I am guessing there is still no way to get the 32bit hypervisor to
> see more than 16G RAM, and I must go to 64bit.
Yes.
> Can I boot a 64bit hypervisor and still keep the same 32bit dom0?
> What're people's experiences running 32bit domUs on
> xen-hypervisor-3.2-1-amd64?
This works if you use the 32bit kernel with a patch from 3.2 or newer on
the dom0.

Bastian

-- 
The heart is not a logical organ.
		-- Dr. Janet Wallace, "The Deadly Years", stardate 3479.4