Re: [Qemu-devel] [PATCH] memory.h: Improve IOMMU related documentation

[Paolo Bonzini <pbonzini@redhat.com>]

On 30/04/2018 14:57, Peter Maydell wrote:
> On 30 April 2018 at 13:54, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> On 30/04/2018 14:24, Peter Maydell wrote:
>>> -    /* Set this up to provide customized IOMMU replay function */
>>> +    /* Set this up to provide customized IOMMU replay function.
>>> +     * Optional method.
>>> +     */
>>>      void (*replay)(IOMMUMemoryRegion *iommu, IOMMUNotifier *notifier);
>>
>> replay is needed if you want to support IOMMU notifiers.  After
>> memory_region_register_iommu_notifier you're only notified about future
>> changes to the mappings; memory_region_iommu_replay calls the replay
>> method so that the IOMMUNotifier is called for each existing mapping.
> 
> Is it then unrelated to record-and-replay ? That's what I guessed
> it was for... Also, some IOMMUs (eg spapr_iommu.c) seem to support
> notifiers but don't implement it.

Yes, it's completely unrelated.  I have no idea why spapr_iommu.c
doesn't need it, so I am CCing the sPAPR and VFIO experts...

Paolo