[LPC] pkeys ABI

Hi,

I am considering submitting a Refereed presentation proposal for LPC,
but I would first like to check if it makes sense to everyone in To/Cc.

The pkeys ABI is heavily underspecified when it comes to asynchronous
kernel interactions, such as signal delivery [1], rseq [2], io_uring
worker threads, etc. Depending on the situation, we might reset the pkey
register to "allow all", or "allow acess to pkey 0 only", or use the
interrupted context's register (even though it is arguably unrelated).
It isn't always consistent across architectures either. 

As Thomas put it, "that's all broken". LPC feels like the right occasion
to summarise where we are, and explore potential solutions.
Unfortunately this topic isn't an obvious fit for any MC, so a Refereed
presentation seems like the least bad option.

Any thoughts/suggestions?

Thanks,
- Kevin

PS: Cc'ing [email protected] as there is no dedicated mailing list
for Refereed presentations.

[1]
https://inbox.sourceware.org/libc-alpha/[email protected]/
[2] https://lore.kernel.org/all/87ikexhbah.ffs@tglx/