On 30/10/2025 09:10, Duan, Zhenzhong wrote: >> From: Avihai Horon <[email protected]> >> On 29/10/2025 11:53, Zhenzhong Duan wrote: >> >> BTW, do you have a real production use case for migration with VFIO >> IOMMU type1 dirty tracking? I mean, is the scenario you described in >> patch #7 a real use case or you just fixed it for completeness? >> If there is no use case, maybe patch #9 is not really needed? > > patch7 is a real use case, in guest, we switch device from IOMMU domain to > block domain and see the issue. > We need to send accurate unmap notification with actual mapping during > migration, for both backend. >
I think the real question is why you are using type1 backend overall for purposes of dirty tracking. type1 dirty tracking just returns everything in the bitmap as 1s. There's no actual dirty tracking and we usually call 'perpectual' dirty tracking because everything DMA mapped as write is always returned as dirty no matter what you do. It doesn't look at pagetable neither for the unmap get dirty. It's only (known) use has been for testing (in the lack of IOMMU HW + IOMMUFD) But reading your statement in a different way: you are saying that you use *two* backends at the same time? Why would you do that?
