aarch64: Memory tagging modes proposal

[Yury Khrustalev]

On Tue, Sep 01, 2026 at 04:16:26PM +0100, Yury Khrustalev wrote:
> On Thu, Aug 27, 2026 at 06:08:27PM -0300, Adhemerval Zanella Netto wrote:
> > 
> ...
>

I think this discussion was useful even if not very successful. It
helped me realised the issue with the 'none' naming as well as the
need to separate use cases of marked and unmarked binaries.
Particularly, we should not allow to override modes set in the binary
marking via a tunable.

I've also revisited the question of Asymmetric tag check fault mode.
It turns out that there will be no PR_MTE_TCF_* constant for this
mode and instead a combination of PR_MTE_TCF_SYNC and PR_MTE_TCF_ASYNC
should be used to enable system-preferred mode that can be configured
via sysfs to be one of the supported modes including Asymmetric.

Rationale for this is described in [1].

I'll send patch for the new tunable shortly.

[1]: https://lore.kernel.org/all/20220309131200.112637-1-broonie@kernel.org/

Thanks,
Yury