Re: [Xen-devel] [PATCH 4/4] x86/APIC: restrict certain messages to BSP

[Jan Beulich <jbeulich@xxxxxxxx>]

On 13.03.2020 17:18, Andrew Cooper wrote:
> On 13/03/2020 09:26, Jan Beulich wrote:
>> All CPUs get an equal setting of EOI broadcast suppression; no need to
>> log one message per CPU, even if it's only in verbose APIC mode.
>>
>> Only the BSP is eligible to possibly get ExtINT enabled; no need to log
>> that it gets disabled on all APs, even if - again - it's only in verbose
>> APIC mode.
> 
> How true is this in practice?

I guess you read "eligible" as "in theory", whereas it is meant as "with
how our [and in particular this] code is working right now". Even if we
decided to switch the CPU to handle ExtINT, it still wouldn't need to be
one message per CPU - it would suffice to issue the message for the one
CPU getting ExtINT enabled.

Jan

> I know it is certainly the recommended configuration, but interrupt
> remapping can definitely point ExtINT at arbitrary CPUs, and IIRC, the
> MP spec simply says that "only one CPU should be configured to receive
> ExtINT".
> 
> I know we definitely have bugs with ExiINT handling, but I haven't had
> time to debug further.
> 
> ~Andrew
> 


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel