On Thu, Feb 22, 2018 at 2:51 PM, Alastair D'Silva [off-list ref] wrote:

On Thu, 2018-02-22 at 14:46 +1100, Balbir Singh wrote:
<snip>

quoted

lpc_size could be added. It's currently useless to the library, but

quoted

doesn't
hurt. The one which was giving me troubles on a previous version of
this
patch was the lpc numa node ID, since that was experimental code
and felt
out of place considering what's been upstreamed in skiboot and
linux so far.

Yeah, I think metadata will evolve for a while till it settle's down.
Since ocxl_ioctl_get_metadata is exposed via uapi, a newer program
calling an older kernel will never work, since the size of that
struct
will always be larger than what the OS supports and our
copy_to_user()
will fail. The other option is for the user program to try all
possible versions till one succeeds, that is bad as well. I think
there are a few ways around it, if we care about this combination.

Balbir Singh.

We have a number of reserved members at the end of the struct which can
be re-purposed for future information (with a corresponding bump of the
version number).

Good point, agreed

Balbir Singh.