Re: [Xen-devel] [PATCH] arm/acpi: hide watchdog timer in GTDT table for dom0

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.11.16 at 03:59, <shankerd@xxxxxxxxxxxxxx> wrote:
> Either we have to hide the watchdog timer section in GTDT or emulate
> watchdog timer block for dom0. Otherwise, system gets panic when
> dom0 accesses its MMIO registers. The current XEN doesn't support
> virtualization of watchdog timer, so hide the watchdog timer section
> for dom0.
> 
> Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>

The mere need for a patch like this is, to me at least, a pretty
clear indication that such black listing models don't work well
(and using white listing instead would likely be too restrictive).
As the same is about to become an issue on x86 too (with
PVHv2) I think there's a need to reconsider how to deal with
ACPI with other than a traditional PV Dom0, namely whether
(a) it wouldn't make sense to expect a little more awareness
by the Dom0 kernel, and
(b) whether we shouldn't unconditionally hand everything to
Dom0 which Xen doesn't explicitly make use of itself (implying
that MMIO regions get suitably prepared either during boot
or on demand).

Jan


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