Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs

[Ingo Molnar]

* Borislav Petkov <bp@xxxxxxxxx> wrote:

> On Tue, Feb 24, 2015 at 04:07:07PM -0800, Andy Lutomirski wrote:
>
> > I'd prefer a different partial solution: encourage 
> > everyone to clear the xstate before making syscalls 
> > (using e.g. vzeroall).  In fact, maybe user code should 
> > aggressively clear newly-unused xstate.
> 
> We don't trust userspace.

We certainly don't, but in this case it's a performance 
optimization detail: if user-space clears unused xstate in 
a way that the CPU recognizes it (for example VZEROALL) 
then it might get faster context switches.

Thanks,

	Ingo
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