Re: [RFC] x86: Avoid CR3 load on compatibility mode with PTI

[Willy Tarreau]

On Mon, Jan 15, 2018 at 11:49:19AM -0800, Dave Hansen wrote:
> If we start disabling PTI willy nilly at points _away_ from the
> capability checks (like for 32-bit binaries, say), then it gets really
> hard to decide if we are doing the right things.
> 
> Also, what's the end goal here?  Run old 32-bit binaries better?  You
> want to weaken the security of the whole implementation to do that?
> Sounds like a bad tradeoff to me.

In fact I understand it differently, which is that by running 32-bit,
he can recover the original performance without sacrifying security.
It's not that bad actually when you think about it since the vast
majority of performance-sensitive software doesn't need to access
even one GB of data.

Willy