Re: [Xen-devel] Adding new custom devices to Xen via QEMU

[Jason Dickens <jdickens@xxxxxxxxxxxxxx>]

Thanks David,

This could very well be the issue, but could you please elaborate?
The questions that come up are the following:
What is the physical address range given to RAM? What range of addresses 
would work for my device?
And, if this is the case, how would I unpopulate the RAM?

There are reasons for the address chosen, and it works on other 
hypervisors (e.g. KVM) so although it might be easiest to change the 
address I really don't want to unless its the only way to keep from a 
Xen modification entirely.
Jason

On 9/30/2016 9:53 AM, David Vrabel wrote:
> On 30/09/16 14:35, Jason Dickens wrote:
> > Hi Wei,
> >
> > Thanks for the response. It make sense to me that if the device were on
> > the PCI bus (or other such bus, e.g. USB) that it could be discovered,
> > at least by an OS. Its something to consider. I should mention that our
> > guest VM doesn't actually use an OS.
> >
> > However, the device is not implemented that as PCI it is simply memory
> > mapped. Technically, in QEMU is has type ISA because it was derived as a
> > modification of the TPM device. Is it possible something is lacking in
> > the QEMU model that Xen needs but KVM doesn't?
> > If the answer is that Xen should not need modification for any new
> > devices then this gives me hope.  You've also inspired some things to
> > try, like whether or not smaller modifications to the TPM device work.
> > One change that is significant to mention is that the physical address
> > range use is anomalous, by which I mean it not in the normal device range.
> Does device MMIO overlap with guest RAM?  If so, you'll need to
> unpopulate the RAM first.
>
> David


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