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

[Thomas Gleixner]

On Mon, Jun 05 2023 at 15:50, Thomas Gleixner wrote:

> 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.

It's also ensured that VMMs do not get confused by this, right?

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