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.
Regards,
Yi Liu
