Re: Design doc of adding ACPI support for arm64 on Xen - version 2

["Roger Pau Monné" <roger.pau@citrix.com>]

El 11/08/15 a les 16.19, Ian Campbell ha escrit:
> On Fri, 2015-08-07 at 10:11 +0800, Shannon Zhao wrote:
>> This document is going to explain the design details of Xen booting with
>> ACPI on ARM. Maybe parts of it may not be appropriate. Any comments are
>> welcome.
> 
> Some small subsets of this seem like they might overlap with what will be
> required for PVH on x86 (a new x86 guest mode not dissimilar to the sole
> ARM guest mode). If so then it would be preferable IMHO if PVH x86 could
> use the same interfaces.
> 
> I've trimmed the quotes to just those bits and CCd some of the PVH people
> (Boris and Roger[0]) in case they have any thoughts.
> 
> Actually, having done the trimming there is only one such bit:
> 
> [...]
>> 4. Map MMIO regions
>> -------------------
>> Register a bus_notifier for platform and amba bus in Linux. Add a new
>> XENMAPSPACE "XENMAPSPACE_dev_mmio". Within the register, check if the
>> device is newly added, then call hypercall XENMEM_add_to_physmap to map
>> the mmio regions.
> 
> Ian.
> 
> [0] Roger is away for a week or so, but I'm expect feedback to be of the
> "we could use one extra field" type rather than "this needs to be done some
> totally different way for x86/PVH" (in which case we wouldn't want to share
> the interface anyway I suppose) so need to block on awaiting that feedback.

This looks right to me. AFAICT this new memory space
(XENMAPSPACE_dev_mmio) will only be available to the hardware domain on
x86. I expect that for DomUs the toolstack will already map the
appropriate MMIO regions when creating the domain if there are
pass-through devices assigned, not sure if that's also the plan on ARM.
IMHO this document should also list the usage of the hypercall parameters:

- space: XENMAPSPACE_dev_mmio.
- idxs: native physical addresses.
- gpfns: guest physical addresses where the mapping should appear.

This is quite obvious but I think it's worth spelling it out.

Roger.