Re: [PATCH v2] nvme: allow 64-bit results in passthru commands

[Keith Busch]

On Mon, Aug 19, 2019 at 11:56:28AM -0700, Sagi Grimberg wrote:
> 
> >> ----- On 16 Aug, 2019, at 15:16, Christoph Hellwig hch@xxxxxx wrote:
> >>> Sorry for not replying to the earlier version, and thanks for doing
> >>> this work.
> >>>
> >>> I wonder if instead of using our own structure we'd just use
> >>> a full nvme SQE for the input and CQE for that output.  Even if we
> >>> reserve a few fields that means we are ready for any newly used
> >>> field (at least until the SQE/CQE sizes are expanded..).
> >>
> >> We could do that, nvme_command and nvme_completion are already UAPI.
> >> On the other hand that would mean not filling out certain fields like
> >> command_id. Can do an approach like this.
> > 
> > Well, we need to pass user space addresses and lengths, which isn't
> > captured in struct nvme_command.
> 
> Isn't simply having a 64 variant simpler?

Could you provide more details on what you mean by this?