Re: KVM RAM limitation

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/03/2010 01:08 PM, Daniel Bareiro wrote:
> On Wednesday, 03 February 2010 11:48:01 -0600,
> Brian Jackson wrote:
>
>    
>>> I'm trying to boot a VM with 2048 MB in a VMHost with Linux 2.6.32.6
>>> and qemu-kvm-0.12.2, but when doing it, I obtain it the following
>>> message:
>>>
>>> qemu: at most 2047 MB RAM can be simulated.
>>>        
>    
>> Are you sure you enabled KVM? Are you sure you are using the KVM
>> binary and not some QEMU binary that's sitting around. This is one of
>> those situations where the KVM command you are running might help.
>> Also the same binary you are running's version ($QEMU_BIN -h | head
>> -n1)
>>      
> wilson:/usr/local/qemu-kvm/bin# ./qemu-system-x86_64 -h | head -n1
> QEMU PC emulator version 0.12.2 (qemu-kvm-0.12.2), Copyright (c) 2003-2008 Fabrice Bellard
>
>
> The procedure that I used to compile qemu-kvm is the same of always: to
> download qemu-kvm-0.12.2, to install the packages (Debian) zlib1g-dev
> and libpci-dev, and to compile of the following way:
>
> # cd qemu-kvm-0.12.2
> # ./configure --prefix=/usr/local/qemu-kvm
> # make
> # make install
>
> Until the moment I never got to use qemu-kvm with VMs of more than 2048
> MB. In an installation that I have with KVM-88 and kernel x86_64 I don't
> have this problem.
>    

QEMU and KVM only support 2GB of memory on a 32-bit host.

Both need to create a userspace mapping of the guests memory.  In a 
32-bit environment, you only have enough usable address space in a 
process to create a 2GB region.

Regards,

Anthony Liguori

> Thanks for your reply.
>
> Regards,
> Daniel
>