Fedora xen - Feb 2007 - memory strangeness

Hi list,
I am a happy user of xen''ed fedora 6. It is working really well (fc6 
domU on fc6 dom0). I have recently added memory to the server (Dell 
Power Edge 2850, latest bios A06) from 2GB to 4GB.
And there is something strange with the total memory report from the OS:

[root@host ~]# uname -a
Linux host 2.6.19-1.2911.fc6xen #1 SMP Sat Feb 10 15:34:39 EST 2007 
x86_64 x86_64 x86_64 GNU/Linux

[root@host ~]# cat /proc/meminfo | grep MemTotal
MemTotal:      3584000 kB

[root@krypton ~]# xm top
...
Mem: 4193664k total, 4184456k used, 9208k free    CPUs: 4 @ 2992MHz
...

Why does it return different value with ''cat /proc/meminfo''
and ''xm top''.
Should I worry about this?
Thanks,
Kfx.