Re: [Xen-devel] [PATCH v2 2/4] x86/apic: force phys mode if interrupt remapping is disabled

[Jan Beulich <jbeulich@xxxxxxxx>]

On 29.11.2019 12:38, Roger Pau Monné  wrote:
> On Fri, Nov 29, 2019 at 12:28:49PM +0100, Roger Pau Monne wrote:
>> Cluster mode can only be used with interrupt remapping support, since
>> the top 16bits of the APIC ID are filled with the cluster ID, and
>> hence on systems where the physical ID is still smaller than 255 the
>> cluster ID is not. Force x2APIC to use physical mode if there's no
>> interrupt remapping support.
>>
>> Note that this requires a further patch in order to enable x2APIC
>> without interrupt remapping support.
>>
>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> This is missing a command line doc update and the logic below ignores
> a user-set x2apic_phys value.

So what would the behavior be in your opinion when the user
has requested cluster mode? I can't see you do much other
than panic()-ing, perhaps it's better to override the request
(as you already do)?

Jan

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