[Xen-devel] [RFC] Device memory mappings for Dom0 on ARM64 ACPI systems

[Stefano Stabellini]

On Fri, 20 Jan 2017, Roger Pau Monné wrote:
> > > > So you need DOM0 to tell the list of regions.
> > > 
> > > Yes, I agree that we need such hypercall ATM, although I think that we might be
> > > able to get rid of it in the long term if we are able to parse the AML tables
> > > from Xen.
> > 
> > Are you suggesting to bring a full AML parser in Xen? If so, it will be much
> > bigger than Xen ARM itself. I would need a strong use case to accept a such
> > thing.
> 
> It could be placed in the init section, and get rid of it after boot. Also, I
> find it hard to believe that an AML parser is bigger than the whole Xen on ARM.
> The OpenBSD folks have a DSDT parser in ~4000 lines of code [0], and that's
> probably way more than what Xen actually needs.

Even if it were actually possible, 4 KLOC is a significant increase in
code size, given that last time I counted Xen on ARM was under 90 KLOC.
Regardless, some AML methods have side effects. I don't know if the plan
of accessing some AML in Xen, then remapping tables and accessing them
again in Dom0 is actually sound. I don't think the spec supports it.