Re: Xen pciback not working: "address space collision: [mem ...] conflicts with System RAM [mem ...]"

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Aug 02, 2013 at 11:07:35AM +0200, Andrea Brugiolo wrote:
> On Mon, Jul 29, 2013 at 01:55:16PM -0400, Konrad Rzeszutek Wilk wrote:
> > On Mon, Jul 29, 2013 at 10:02:03AM +0100, Ian Campbell wrote:
> > > On Fri, 2013-07-26 at 12:32 +0200, Andrea Brugiolo wrote:
> > > > Good Morning
> > > > 
> > > > I cannot do pciback anymore for both my second scsi controller and my
> > > > second network card: when I try to pass the device to the domU I get
> > > > this error in system logs:
> > > > 
> > > >   ... address space collision: [mem ...] conflicts with System RAM [mem ...]
> > > 
> > > By eliding the actually addresses you've omitted something which I think
> > > might be interesting:
> > >         [mem 0xf9e00000-0xf9e1ffff 64bit] conflicts with System RAM [mem 0x00100000-0x4007fffff]
> > > 
> > > Note that there is not any actual overlap in those two sets of addresses...
> > 
> > I think it is:
> > mem 0xf9e00000-0xf9e1ffff
> > mem 0x00100000-0x4007fffff
> > 
> > The RAM region is pretty much all of the memory. This looks like the 'e820_hole'
> > parameter is not being used? (It only works for xl btw).
> > 
> > > 
> > > Might be that the check is truncating something, or maybe it is
> > > confusing MFN and PFN and so getting a false +ve. Both wild guesses
> > > having not even looked at the code...
> > > 
> > > > The problem is described here:
> > > > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=717353 and is
> > > > blocking my backup system which is based on a scsi tape changer
> > > > attached to the domU.
> > > 
> > > What do the guest and host e820 map look like? Actually the full dmesg
> > > for the hypervisor, dom0 and domU kernels would be useful to provide, I
> > > expect.
> > 
> > And the guest config pls.
> 
> At last I have managed to reboot the system. Please find the attachments:
> 
>  - dom0 dmesg
>  - domU dmesg
>  - domU configuration
> 
> Recall:
> 
>  - dom0 is Debian GNU/Linux 7.1 with Debian kernel 3.2.0-4-amd64 (3.2.46-1)
>  - domU is Debian GNU/Linux 6.0.7 with the same kernel
> 
> The "address space collision" shows up for both the devices I am
> trying to pass as I have been doing for years.

So you are using 'xm', but 'xm' does not support 'e820_hole=1'. You need
to use 'xl'. The domU E820 is as I suspected without the host E820 which
is why you are hitting the issue.

Note, I did at some point post an implementation of 'e820_hole=1'
argument for Xend, but since Xen is being deprecated ... it didn't make
much sense adding it in.

Awaiting your response with the usage of 'xl'.

Thanks!