Re: [PATCH 1/2] xen/arm: Add imx8q{m,x} platform glue

[Julien Grall <julien@xen.org>]

Hi John,

 > Ping on the watchdog discussion bits.

Sorry for the late reply.

On 06/03/2024 13:13, John Ernberg wrote:
> On 2/9/24 14:14, John Ernberg wrote:
>>
>>>     * IMX_SIP_TIMER_*:  This seems to be related to the watchdog.
>>> Shouldn't dom0 rely on the watchdog provided by Xen instead? So those
>>> call will be used by Xen.
>>
>> That is indeed a watchdog SIP, and also for setting the SoC internal RTC
>> if it is being used.
>>
>> I looked around if there was previous discussion and only really found [3].
>> Is the xen/xen/include/watchdog.h header meant to be for this kind of
>> watchdog support or is that more for the VM watchdog? Looking at the x86
>> ACPI NMI watchdog it seems like the former, but I have never worked with
>> x86 nor ACPI.

include/watchdog.h contains helper to configure the watchdog for Xen. We 
also have per-VM watchdog and this is configured by the hypercall 
SCHEDOP_watchdog.

>>
>> Currently forwarding it to Dom0 has not caused any watchdog resets with
>> our watchdog timeout settings, our specific Dom0 setup and VM count.

IIUC, the SMC API for the watchdog would be similar to the ACPI NMI 
watchdog. So I think it would make more sense if this is not exposed to 
dom0 (even if Xen is doing nothing with it).

Can you try to hide the SMCs and check if dom0 still behave properly?

Cheers,

-- 
Julien Grall