[Fedora-xen] Not seeing all RAM

[Kanwar Ranbir Sandhu]

On Tue, 2007-07-03 at 15:23 +0100, Daniel P. Berrange wrote:
> Let me guest - you are running a 32-bit kernel on the machine ? If so
> the problem is likely that the BOIS is remapping a portion of memory
> above the 4 GB mark, to make room for PCI device DMA zones. A 32-bit
> kernel though can only access physical addrs upto 4 GB, so it can't
> see the remapped memory.

I'm aware of that, but in my case it doesn't make sense: the server only
has 3 GB of RAM.  The kernel just doesn't see all of it.

I was using kernel-xen-2.6.19-1.2895.fc6 and about 512 MB were missing.
After upgrading to kernel-xen-2.6.20-1.2962.fc6, the kernel can see more
memory, but I'm still missing about 256 MB.

I'm going to open a new bug report for this.

> PCI device mapping to DomUs is insanely fragile, whether it works or not
> is mostly luck. In this case since you added more memory, the locaiton of
> the PCI device's DMA zone probably changed and by (bad) luck is no longer
> accessible to the DomU or something like that.

That's what I figured, though I don't know all of the details.  However,
with the new kernel being able to see more of the 3 GB, the domU is
working again.  The pci device I'm hiding from dom0 is being properly
handed to the domU.

Regards,

Ranbir
-- 
Kanwar Ranbir Sandhu
Linux 2.6.20-1.2944.fc6 i686 GNU/Linux 
10:42:35 up 20:50, 2 users, load average: 2.15, 2.16, 1.45