Re: [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits

[Vincenzo Frascino]

On 2/23/21 12:49 PM, Will Deacon wrote:
>>> I totally agree on this point. In the case of runtime switching we might need
>>> the rethink completely the strategy and depends a lot on what we want to allow
>>> and what not. For the kernel I imagine we will need to expose something in sysfs
>>> that affects all the cores and then maybe stop_machine() to propagate it to all
>>> the cores. Do you think having some of the cores running in sync mode and some
>>> in async is a viable solution?
>> stop_machine() is an option indeed. I think it's still possible to run
>> some cores in async while others in sync but the static key here would
>> only be toggled when no async CPUs are left.
> Just as a general point, but if we expose stop_machine() via sysfs we
> probably want to limit that to privileged users so you can't DoS the system
> by spamming into the file.

I agree, if we ever introduce the runtime switching and go for this option we
should make sure that we do it safely.

-- 
Regards,
Vincenzo