Re: [PATCH v8 26/33] x86/fred: allow single-step trap and NMI when starting a new thread

[Thomas Gleixner]

On Mon, Apr 10 2023 at 01:14, Xin Li wrote:
> Allow single-step trap and NMI when starting a new thread, thus once
> the new thread returns to ring3, single-step trap and NMI are both
> enabled immediately.
>
> High-order 48 bits above the lowest 16 bit CS are discarded by the
> legacy IRET instruction, thus can be set unconditionally, even when
> FRED is not enabled.

I assume this has been validated to be true on _all_ CPU incarnations of
_all_ x86 vendors.

If so, then please document it. If not, then go back to the drawing
board.

Thanks,

        tglx