Re: [Xen-devel] Xen: Support for mapping OperationRegion in ACPI ASL

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 20 Dec 2016, Jan Beulich wrote:
> >>> On 20.12.16 at 00:01, <sstabellini@xxxxxxxxxx> wrote:
> > This is actually not an ARM specific question, so changing the subject
> > and CC'ing more people.
> > 
> > On Wed, 14 Dec 2016, Konrad Rzeszutek Wilk wrote:
> >> On Tue, Dec 13, 2016 at 07:14:27PM -0600, Jiandi An wrote:
> >> > Xen currently does not handle mapping of MMIO regions specified under 
> > OperationRegion in ACPI ASL.  OperationRegion is well defined in ACPI 
> > specification.  I'm seeking for architectural direction on adding support 
> > for 
> > mapping OperationRegion.
> >> > 
> >> > Some context here.  Mapping of resources specificed under _CRS in ACPI 
> >> > is 
> > handled by dom0 requesting Xen to map as platform devices are added.  
> > https://lwn.net/Articles/674666/ provided service xen_map_device_mmio() in 
> > dom0 to call Xen to map and it's done so by registering 
> > xen_platform_notifier() platform bus driver.  This covers the platform 
> > devices.
> >> > 
> >> > The OperationRegion access in dom0 is in acpica path.  The following is 
> >> > a 
> > stack of the code path where OperationRegion is parsed.  
> 
> But aren't such regions required to be claimed by resource
> declarations elsewhere? I don't think the mapping (into the p2m)
> should happen during an access attempt, but much earlier. But
> perhaps I'm missing some context ...

Please correct me if I am wrong, but we are talking about ACPI
initialization here. In fact, acpi_init was one of the first functions
in the callstack of the previous email. So yes, we are trying to map the
regions when they are discovered during ACPI initialization, which is as
early as possible I think.

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