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

[Catalin Marinas]

On Tue, Feb 23, 2021 at 10:56:46AM +0000, Vincenzo Frascino wrote:
> On 2/22/21 5:58 PM, Catalin Marinas wrote:
> > We'll still have an issue with dynamically switching the async/sync mode
> > at run-time. Luckily kasan doesn't do this now. The problem is that
> > until the last CPU have been switched from async to sync, we can't
> > toggle the static label. When switching from sync to async, we need
> > to do it on the first CPU being switched.
> 
> 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.

> Probably it is worth to discuss it further once we cross that bridge.

Yes. For now, a warning should do so that we don't forget.

-- 
Catalin