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> else > domain->domain.geometry.aperture_end = __DOMAIN_MAX_ADDR(domain->gaw); > > i.e. both are initialized around domain->gaw. > > but the new way has difference between first-stage and second-stage as > Jason pointed out already. > > Baolu, what is the number in "Using xxx-bit DMA addresses" when > using second-stage? He said 42. Indeed Chaitanya's dmesg has this: [ 0.079787] DMAR: Host address width 42 Which I think explains the bug. The dmar->width is being ignored by the driver except for that print. > my understanding of various 'gaw' fields are only about second stage, but > maybe there is something we overlooked... That is what the spec says: MGAW: Maximum Guest Address Width This field indicates the maximum guest physical address width supported by second-stage translation in remapping hardware. The Maximum Guest Address Width (MGAW) is computed as (N+1), where N is the valued reported in this field. For example, a hardware implementation supporting 48-bit MGAW reports a value of 47 (101111b) in this fiel Seems very clear it is related to the second stage in that paragraph.. So, I think what has happened here is the old driver mis-used mgaw for the first stage: addr_width = agaw_to_width(iommu->agaw); if (addr_width > cap_mgaw(iommu->cap)) addr_width = cap_mgaw(iommu->cap); domain->gaw = addr_width; And fully ignored dmar->width, which happened to work because mgaw < dmar->width So we should be using dmar->width to constrain the first stage and expect that mgaw is less than dmar->width ? Jason