On 2021/6/1 10:36, Jason Wang wrote: > > 在 2021/5/31 下午4:41, Liu Yi L 写道: >>> I guess VFIO_ATTACH_IOASID will fail if the underlayer doesn't support >>> hardware nesting. Or is there way to detect the capability before? >> I think it could fail in the IOASID_CREATE_NESTING. If the gpa_ioasid >> is not able to support nesting, then should fail it. >> >>> I think GET_INFO only works after the ATTACH. >> yes. After attaching to gpa_ioasid, userspace could GET_INFO on the >> gpa_ioasid and check if nesting is supported or not. right? > > > Some more questions: > > 1) Is the handle returned by IOASID_ALLOC an fd? > 2) If yes, what's the reason for not simply use the fd opened from /dev/ioas. (This is the question that is not answered) and what happens if we call GET_INFO for the ioasid_fd? > 3) If not, how GET_INFO work? It seems that the return value from IOASID_ALLOC is an IOASID number in the ioasid_data struct, then when calling GET_INFO, we should convey this IOASID number to get the associated I/O address space attributes (depend on the physical IOMMU, which could be discovered when attaching a device to the IOASID fd or number), right? Thanks, Shenming
