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SubjectRe: [PATCH v3 0/4] Intel MPX support

* Ren Qiaowei <qiaowei.ren@intel.com> wrote:

> >> MPX kernel code, namely this patchset, has mainly the 2
> >> responsibilities: provide handlers for bounds faults (#BR), and
> >> manage bounds memory.
> >
> > AFAICS the kernel side implementation causes no runtime overhead
> > for non-MPX workloads, and also causes no runtime overhead for
> > non-MPX hardware, right?
>
> Yes.

Actually, I think that's not entirely true.

For example if within the same mm there's a lot of non-MPX threads and
an MPX thread, then the MMU notifier will be called for MMU operations
of every non-MPX thread as well!

So MPX state of a thread will slow down all the other non-MPX threads
as well.

The statement is only true for non-MPX tasks that have their separate
mm's that does not have a single MPX thread.

Thanks,

Ingo


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