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

[Gordan Bobic <gordan@xxxxxxxxxx>]

On Fri, 2 Aug 2013 08:06:00 -0400, Konrad Rzeszutek Wilk 
<konrad.wilk@xxxxxxxxxx> wrote:
> On Fri, Aug 02, 2013 at 10:27:04AM +0100, Gordan Bobic wrote:
> > On Fri, 2 Aug 2013 11:07:35 +0200, Andrea Brugiolo
> > <andrea@xxxxxxxxxxxx> 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).
> >
> > Where is the e820_hole option documented and what does it do?
> It should be in the manpage (man xl.cfg). Here is a copy-n-paste:
>     e820_host=BOOLEAN
>         Selects whether to expose the host e820 (memory map) to the 
> guest
>         via the virtual e820. When this option is false (0) the guest
>         pseudo-physical address space consists of a single contiguous 
> RAM
>         region. When this option is specified the virtual e820 
> instead
>         reflects the host e820 and contains the same PCI holes. The 
> total
>         amount of RAM represented by the memory map is always the 
> same, this
>         option configures only how it is laid out.
>
>         Exposing the host e820 to the guest gives the guest kernel 
> the
>         opportunity to set aside the required part of its 
> pseudo-physical
>         address space in order to provide address space to map 
> passedthrough
>         PCI devices. It is guest Operating System dependent whether 
> this
>         option is required, specifically it is required when using a
>         mainline Linux ("pvops") kernel. This option defaults to true 
> (1) if
>         any PCI passthrough devices are configured and false (0) 
> otherwise.
>         If you do not configure any passthrough devices at domain 
> creation
>         time but expect to hotplug devices later then you should set 
> this
>         option. Conversely if your particular guest kernel does not 
> require
>         this behaviour then it is safe to allow this to be enabled 
> but you
>         may wish to disable it anyway.
Ah, so this was a typo above. s/e820_hole/e820_host/

Thanks for clarifying.

Gordan

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