Re: [Qemu-devel] [RESEND PATCH v8 1/4] apic: map APIC's MMIO region at each CPU's address space

[Paolo Bonzini]

On 25/06/2015 18:10, Andreas Färber wrote:
> Am 25.06.2015 um 18:02 schrieb Paolo Bonzini:
>> On 25/06/2015 18:00, Andreas Färber wrote:
>>>> -    if (!mmio_registered) {
>>>> -        ICCBus *b = ICC_BUS(qdev_get_parent_bus(dev));
>>>> -        memory_region_add_subregion(b->apic_address_space, 0, 
>>>> &s->io_memory);
>>>> -        mmio_registered = true;
>>>> -    }
>>>> +
>>>> +    root = address_space_root_memory_region(cpu->as);
>>>> +    memory_region_add_subregion_overlap(root,
>>>> +                                        s->apicbase & 
>>>> MSR_IA32_APICBASE_BASE,
>>>> +                                        &s->io_memory,
>>>> +                                        0x1000);
>>>>  
>>
>> I had already remarked that this patch is wrong.  cpu->as is completely
>> unused on KVM, for example.
> 
> Ah, then I don't understand this [RESEND]. ;)
> Either way, not on my plate ATM, it seems.
> 
> Did you also outline how it is supposed to be done instead?

I said "I think this patch is incorrect, because you do not install a
separate address space for each CPU.  Also, the CPU address space is
only used with TCG so it should be guarded by "if (tcg_enabled())"."

By the way, now TCG _is_ installing a separate address space per CPU
already, so the patch can simply guard the code with "if (tcg_enabled())".

Paolo