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Re: [Xen-users] X86_64 and 4GB RAM

On Sat, Apr 28, 2007 at 02:13:07PM +0100, John Hannfield wrote:

> I have an odd problem on a dual processor, dual core Opteron system.
> Obviosously it is x86_64 so should have no problem large amounts of
> RAM. The system has 4 GB installed (2GB on each processor).
> If I boot the system with a fresh install of Debian Etch it sees all the 
> memory
> fine. dmesg reports:
> Memory: 4107008k/5242880k available (1929k kernel code, 86836k
> reserved, 864k data, 176k init)
> However if I boot a xen-3.0.3  kernel, it only sees about half of this:
> The xen dmesg reports:
> Memory: 183852k/270336k available (3531k kernel code, 77948k reserved,
> 1250k data, 208k init)

Can you check if this problem is related to debian bug #419994?

Xen system gets memory map directly from grub loader, differently to
plain linux kernel. On some systems grub have trouble calling BIOS
function 0x810 int 0x15 and falls back to function 0x801, which
cannot report full memory in presence of PCI memory hole.

You can easily check that, just try command displaymem in grub command
line. If it shows full memory map then I am wrong and your problem is
unrelated to mine. 

Great software without the knowledge to run it is pretty useless.
(Linux Gazette #1)

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