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

[Julien Grall <julien.grall@xxxxxxx>]

Hi Shanker,

On 29/11/2016 02:59, Shanker Donthineni 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.
IHMO, the patch description is not really accurate. You are removing the 
platform timer array that contains watchdog but also Block Timer.
Whilst you mention watchdog, you don't have a word on the Block Timer.

Taking a step back, DOM0 is not able to use it because it does not 
request to map the memory region (this is the behavior expected for PCI 
and AMBA devices). So this is a bug in the kernel for me.
Assuming this would be fixed, what would be the drawback to give access 
to dom0 to the watchdogs?
My worry with that change is what if in the future we decide to expose 
watchdog to DOM0? Linux will still not be ready, unless we have Xen to 
map those regions at DOM0 build time. That would break the design we 
have for ACPI.
Regards,

--
Julien Grall

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