>-----Original Message----- >From: Liu, Yi L <[email protected]> >Subject: Re: [PATCH v2 6/8] intel_iommu: Fix unmap_bitmap failure with >legacy VFIO backend > > > >On 2025/10/20 16:03, Duan, Zhenzhong wrote: >> >> >>> -----Original Message----- >>> From: Liu, Yi L <[email protected]> >>> Subject: Re: [PATCH v2 6/8] intel_iommu: Fix unmap_bitmap failure with >>> legacy VFIO backend >>> >>> On 2025/10/17 16:22, Zhenzhong Duan wrote: >>>> If a VFIO device in guest switches from IOMMU domain to block domain, >>>> vtd_address_space_unmap() is called to unmap whole address space. >>>> >>>> If that happens during migration, migration fails with legacy VFIO >>>> backend as below: >>>> >>>> Status: failed (vfio_container_dma_unmap(0x561bbbd92d90, >>> 0x100000000000, 0x100000000000) = -7 (Argument list too long)) >>>> >>>> Because legacy VFIO limits maximum bitmap size to 256MB which maps >to >>> 8TB on >>>> 4K page system, when 16TB sized UNMAP notification is sent, >>> unmap_bitmap >>>> ioctl fails. >>> >>> It would be great to add some words to note why vIOMMU can trigger >this. >> >> Hi Yi, I think the first sentence in description is explaining that? >> >> "If a VFIO device in guest switches from IOMMU domain to block domain, >> vtd_address_space_unmap() is called to unmap whole address space." > >aha, yes. I was trying to mark it is NOT necessarily related to VM >memory size. Could you note that the address space is guest IOVA which >is not system memory?
Sure, will do Thanks Zhenzhong
