Re: [PATCH v1 06/11] KVM: x86: use hardware-compatible format for APIC ID register

[Radim KrÄmÃÅ]

2016-07-01 17:07+0200, Paolo Bonzini:
> On 01/07/2016 16:54, Radim KrÄmÃÅ wrote:
>>> >                                                                (Hint: we
>>> > want kvm-unit-tests for this).
>> :) Something like this?
>> 
>>   enable_xapic()
>>   id = apic_id()
>>   set_apic_id(id+1) // ?
>>   enable_x2apic()
>>   id == apic_id() & 0xff
>>   disable_apic()
>>   enable_xapic()
>>   id == apic_id()
>> 
> 
> Yes, plus checking that it "moves" appropriately between low and high bits.

x2APIC cannot use MMIO interface, so apic_id() already does the best we
can ... if KVM is shifting wrong somwhere, then the id should differ.