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

On Sat, Apr 28, 2007 at 05:07:36PM +0100, John Hannfield wrote:
> Hi Rafal.
> That is odd. So it only report about 4 MB or memory?

Grub detects about 3G total usable memory.

> >Please send memory map from linux kernel that correctly detects all
> >memory.
> OK, for a vanilla linux boot (Debian Etch AMD64), I get this e820 in the
> dmesg.
> BIOS-provided physical RAM map:
> BIOS-e820: 0000000000000000 - 000000000009dc00 (usable)
> BIOS-e820: 000000000009dc00 - 00000000000a0000 (reserved)
> BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
> BIOS-e820: 0000000000100000 - 00000000bfff0000 (usable)

grub memory map ends here

> BIOS-e820: 00000000bfff0000 - 00000000bfffe000 (ACPI data)
> BIOS-e820: 00000000bfffe000 - 00000000c0000000 (ACPI NVS)
> BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
> BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
> BIOS-e820: 00000000fee00000 - 00000000fef00000 (reserved)
> BIOS-e820: 00000000ff700000 - 0000000100000000 (reserved)

some reserved regions, acpi and pci memory hole

> BIOS-e820: 0000000100000000 - 0000000140000000 (usable)

Look, there is! 1GB of RAM starting at address 4GB.

> Any ideas what the problem is?

There is difference between grub and native linux memory map.
Strange, both of them gets it from BIOS e820 function.

Maybe after all, our problems are similar. We both have systems where
grub detects memory map wrongly. In my case -- entirely wrong, no single
region in memory map. In yours some regions are missing.

Can you try patched version od grub? Try first patch from message 
or this:

On my system both of them make grub works correctly [1].
(And full 4GB memory in Xen)

[1] Sadly, I don't know why this patches helps.
Great software without the knowledge to run it is pretty useless.
(Linux Gazette #1)

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