Re: [PATCH v3 03/11] x86/vlapic: introduce an EOI callback mechanism

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.04.2021 18:27, Roger Pau Monné wrote:
> On Wed, Apr 07, 2021 at 04:55:43PM +0200, Jan Beulich wrote:
>> On 31.03.2021 12:32, Roger Pau Monne wrote:
>>> Add a new vlapic_set_irq_callback helper in order to inject a vector
>>> and set a callback to be executed when the guest performs the end of
>>> interrupt acknowledgment.
>>>
>>> Such functionality will be used to migrate the current ad hoc handling
>>> done in vlapic_handle_EOI for the vectors that require some logic to
>>> be executed when the end of interrupt is performed.
>>>
>>> The setter of the callback will be in charge for setting the callback
>>> again on resume. That is the reason why vlapic_set_callback is not a
>>> static function.
>>
>> I'm struggling with your use of "resume" here: Resuming from S3
>> doesn't require re-doing anything that's kept in memory, does it?
>> So what meaning does the word have here?
> 
> Right, I can see the confusion. Resume here means a guest being
> migrated or restored, not Xen itself being resumed. Callbacks are not
> part of the exported guest state, and hence any emulated device that
> requires a callback will have to register it as part of loading the
> saved state.
> 
>> Apart from this, and with the xzalloc_array() change requested
>> by Andrew, this looks good to me.

In which case with this change and "resume" replaced suitably in the
description
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan