On Tue, Mar 22, 2022 at 10:40:27PM +0530, Kanchan Joshi wrote: > On Fri, Mar 11, 2022 at 11:57 AM Christoph Hellwig <hch@xxxxxx> wrote: > > > And that's because this ioctl requires additional "__u64 result;" to > > > be updated within "struct nvme_passthru_cmd64". > > > To update that during completion, we need, at the least, the result > > > field to be a pointer "__u64 result_ptr" inside the struct > > > nvme_passthru_cmd64. > > > Do you see that is possible without adding a new passthru ioctl in nvme? > > > > We don't need a new passthrough ioctl in nvme. > Right. Maybe it is easier for applications if they get to use the same > ioctl opcode/structure that they know well already. I disagree. Reusing the same opcode and/or structure for something fundamentally different creates major confusion. Don't do it. > >From all that we discussed, maybe the path forward could be this: > - inline-cmd/big-sqe is useful if paired with big-cqe. Drop big-sqe > for now if we cannot go the big-cqe route. > - use only indirect-cmd as this requires nothing special, just regular > sqe and cqe. We can support all passthru commands with a lot less > code. No new ioctl in nvme, so same semantics. For common commands > (i.e. read/write) we can still avoid updating the result (put_user > cost will go). > > Please suggest if we should approach this any differently in v2. Personally I think larger SQEs and CQEs are the only sensible interface here. Everything else just fails like a horrible hack I would not want to support in NVMe.
