>-----Original Message----- >From: Liu, Yi L <[email protected]> >Subject: Re: [PATCH v6 10/22] intel_iommu: Check for compatibility with >IOMMUFD backed device when x-flts=on > >On 2025/9/18 16:57, Zhenzhong Duan wrote: >> When vIOMMU is configured x-flts=on in scalable mode, first stage page >table >> is passed to host to construct nested page table for passthrough devices. >> >> We need to check compatibility of some critical IOMMU capabilities >between >> vIOMMU and host IOMMU to ensure guest first stage page table could be >used by >> host. >> >> For instance, vIOMMU supports first stage 1GB large page mapping, but >host does >> not, then this IOMMUFD backed device should fail. >> >> Even of the checks pass, for now we willingly reject the association because >> all the bits are not there yet, it will be relaxed in the end of this series. > >might be good to note that nested cap is required but it's already >covered in the core, so this patch does not check it. Otherwise, it >would be a question why it is not added without checking previous comments.
Sure, will add: "Note vIOMMU has exposed IOMMU_HWPT_ALLOC_NEST_PARENT flag to force VFIO core to create nesting parent HWPT, if host doesn't support nested translation, the creation will fail. So no need to check nested capability here." Thanks Zhenzhong
