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Re: [Xen-devel] PCI Pass-through / Config Space emulation for ARM64

On Mon, Jul 02, 2018 at 04:16:05PM +0530, Manish Jaggi wrote:
> Hi All,
> PCI-PT and PCI config space emulation have been in discussion for quite a
> long time.
> We had started some work on this in past and in LEG-XEN but that didnt go
> far and the group is closed.
> I believe that PCI-PT is a feature which would be suitable for not only for
> servers but for embedded platforms as well.
> I would like know the interest in the developer community on this, so that
> we can be
> able to complete this in the time frame of 4.12 release.

I'm not involved with the ARM side, but I think targeting
ARM pci-passthrough for 4.12 might be too optimistic. AFAICT ARM
doesn't yet have any kind of pci support, so you will have to:

 - Get Xen to access the pci config space on ARM.
 - Implement trapping for pci config accesses for ARM guests.
 - Enable vpci and implement the arch specific hooks for MSI and MSI-X
   interrupt routing.
 - Audit the current vpci code and implement the missing features (and
   restrictions) so it can be used by unprivileged domains. vpci ATM
   is only used by PVH Dom0, and that's a trusted domain.

That's in my opinion quite a lot of work, and I'm not sure a lot of
this can be done concurrently. Each step depends on the previous one
being functional (except for the last one that can be implemented on
x86 right now).


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