Messages in this thread | | | Subject | Re: [RFC] /dev/ioasid uAPI proposal | From | Jason Wang <> | Date | Tue, 1 Jun 2021 13:10:30 +0800 |
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在 2021/6/1 下午12:27, Shenming Lu 写道: > On 2021/6/1 10:36, Jason Wang wrote: >> 在 2021/5/31 下å�ˆ4:41, Liu Yi L 写é�“: >>>> 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?
Right, but the question is why need such indirection? Unless there's a case that you need to create multiple IOASIDs per ioasid fd. It's more simpler to attach the metadata into the ioasid fd itself.
Thanks
> > Thanks, > Shenming >
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