Re: [PATCH 00/33] hw/cpu/arm: Remove one use of qemu_get_cpu() in A7/A15 MPCore priv

[Fabiano Rosas <farosas@suse.de>]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> +Peter/Fabiano
>
> On 2/1/24 17:41, Cédric Le Goater wrote:
>> On 1/2/24 17:15, Philippe Mathieu-Daudé wrote:
>>> Hi Cédric,
>>>
>>> On 2/1/24 15:55, Cédric Le Goater wrote:
>>>> On 12/12/23 17:29, Philippe Mathieu-Daudé wrote:
>>>>> Hi,
>>>>>
>>>>> When a MPCore cluster is used, the Cortex-A cores belong the the
>>>>> cluster container, not to the board/soc layer. This series move
>>>>> the creation of vCPUs to the MPCore private container.
>>>>>
>>>>> Doing so we consolidate the QOM model, moving common code in a
>>>>> central place (abstract MPCore parent).
>>>>
>>>> Changing the QOM hierarchy has an impact on the state of the machine
>>>> and some fixups are then required to maintain migration compatibility.
>>>> This can become a real headache for KVM machines like virt for which
>>>> migration compatibility is a feature, less for emulated ones.
>>>
>>> All changes are either moving properties (which are not migrated)
>>> or moving non-migrated QOM members (i.e. pointers of ARMCPU, which
>>> is still migrated elsewhere). So I don't see any obvious migration
>>> problem, but I might be missing something, so I Cc'ed Juan :>

FWIW, I didn't spot anything problematic either.

I've ran this through my migration compatibility series [1] and it
doesn't regress aarch64 migration from/to 8.2. The tests use '-M
virt -cpu max', so the cortex-a7 and cortex-a15 are not covered. I don't
think we even support migration of anything non-KVM on arm.

1- https://gitlab.com/farosas/qemu/-/jobs/5853599533

>> We broke migration compatibility by moving the IC object in the QOM
>> hierarchy of the pseries machines in the past. These changes might
>> be different. Here is the QOM tree of the ast2600 SoC.
>> 
>> before :
>> 
>>    /soc (ast2600-a3)
>>      /a7mpcore (a15mpcore_priv)
>>        /a15mp-priv-container[0] (memory-region)
>>        /gic (arm_gic)
>>          /gic_cpu[0] (memory-region)
>>          /gic_cpu[1] (memory-region)
>>          /gic_cpu[2] (memory-region)
>>          /gic_dist[0] (memory-region)
>>          /gic_vcpu[0] (memory-region)
>>          /gic_viface[0] (memory-region)
>>          /gic_viface[1] (memory-region)
>>          /gic_viface[2] (memory-region)
>>      /cpu[0] (cortex-a7-arm-cpu)
>>      /cpu[1] (cortex-a7-arm-cpu)
>> 
>> after :
>> 
>>    /soc (ast2600-a3)
>>      /a7mpcore (a7mpcore_priv)
>>        /cpu[0] (cortex-a7-arm-cpu)
>>        /cpu[1] (cortex-a7-arm-cpu)
>>        /gic (arm_gic)
>>          /gic_cpu[0] (memory-region)
>>          /gic_cpu[1] (memory-region)
>>          /gic_cpu[2] (memory-region)
>>          /gic_dist[0] (memory-region)
>>        /mpcore-priv-container[0] (memory-region)
>> 
>> 
>> Thanks,
>> 
>> C.
>> 
>> 
>>