On 2021/1/29 15:49, Paolo Bonzini wrote:
> On 28/01/21 21:02, Dr. David Alan Gilbert wrote:
>> * Paolo Bonzini (pbonz...@redhat.com) wrote:
>>> On 11/01/21 08:34, Keqian Zhu wrote:
>>>> +static void vfio_listener_log_start(MemoryListener *listener,
>>>> + MemoryRegionSection *section,
>>>> + int old, int new)
>>>> +{
>>>> + VFIOContainer *container = container_of(listener, VFIOContainer,
>>>> listener);
>>>> +
>>>> + vfio_set_dirty_page_tracking(container, true);
>>>> +}
>>>
>>> This would enable dirty page tracking also just for having a framebuffer
>>> (DIRTY_MEMORY_VGA). Technically it would be correct, but it would also be
>>> more heavyweight than expected.
>>
>> Wouldn't that only happen on emulated video devices?
>
> Yes, but still it's not impossible to have both an emulated VGA and an
> assigned GPU or vGPU.
>
>>> In order to only cover live migration, you can use the log_global_start and
>>> log_global_stop callbacks instead.
>>>
>>> If you want to use log_start and log_stop, you need to add respectively
>>>
>>> if (old != 0) {
>>> return;
>>> }
>>>
>>> and
>>>
>>> if (new != 0) {
>>> return;
>>> }
>>
>> Why 0, wouldn't you be checking for DIRTY_LOG_MIGRATION somewhere?
>
> Actually thinking more about it log_start/log_stop are just wrong, because
> they would be called many times, for each MemoryRegionSection.
Agree. This will be called for each MemoryRegionSection and each time when
dirty_log_mask changed.
KVM uses log_start/log_stop, because it can start dirty tracking for every
memslot individually, but vfio just has global start/stop semantics.
Anyway, use global start/stop is correct choice.
Thanks,
Keqian
>
> Paolo
>
> .
>
