Re: [Qemu-ppc] [RFC ppc-next PATCH 3/6] memory: add memory_region_to_address()

[Alexander Graf]

On 21.03.2013, at 12:32, Peter Maydell wrote:

> On 21 March 2013 11:29, Alexander Graf <address@hidden> wrote:
>> On 21.03.2013, at 12:22, Peter Maydell wrote:
>>> We already nest the VGIC inside another memory region (the a15mpcore
>>> container), and it works fine. This function is just iterating through
>>> "everything any device asked me to tell the kernel about".
>> 
>> So kda is the real physical offset? I'm having a hard time reading that code 
>> :). According to this function:
>> 
>> static void kvm_arm_devlistener_add(MemoryListener *listener,
>>                                    MemoryRegionSection *section)
>> {
>>    KVMDevice *kd;
>> 
>>    QSLIST_FOREACH(kd, &kvm_devices_head, entries) {
>>        if (section->mr == kd->mr) {
>>            kd->kda.addr = section->offset_within_address_space;
>>        }
>>    }
>> }
>> 
>> it's only the offset within its parent region, which would mean it's broken, 
>> no?
> 
> Address spaces are not the same thing as memory regions :-)
> The only address space involved here is the system address space.
> (As I say, we currently assume we only get mapped into one address
> space, but that could be fixed if necessary.)

Interesting. Oh well, I'll leave that one to Scott to figure out ;).

So what if I want to write an in-kernel IDE PIO accelerator? Or even better 
yet: An AHCI accelerator that has one MMIO BAR and another PIO BAR that can be 
remapped by the guest at any time?

The distinction on whether a region is handled by KVM really needs to be done 
by the device model.


Alex