Xen users - Jul 2012 - dom0_mem=max:xxx required after linux 3.3 on AMD

Hi,

I have encountered a problem with three different AMD platforms when 
trying to user a kernel release >=3.3 with xen-4.1.2 and xen-unstable.  
When the xen.gz command line has dom0_mem=1G the dom0 will crash 
immediately after Xen trys to boot the kernel.  However it semes that if 
I specify dom0_mem=max:1G then the system will start correctly.  (I have 
only verified this on one system but I will try the other two at the 
earliest opportunity.)  I have exactly the same kernel on an Intel 
platform but this does not show the same behaviour.

Has anyone else observed a similar problem and should it be considered a 
bug?

Thanks,
James

If this is any help: my dom0 boots fine..

CPU: AMD Phenom 2 1090T
Kernel: 3.4.2 openSuse
dom0: Debian Wheezy
Xen: 4.1.3-rc2-pre
kernel xen line: "multiboot /boot/xen.gz dom0_mem=2048M iommu=1
loglvl=all guest_loglvl=all"