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SubjectRe: [PATCH 00/31 v2] PTI support for x86_32
On Fri 2018-02-09 17:47:43, Andy Lutomirski wrote:
> On Fri, Feb 9, 2018 at 9:25 AM, Joerg Roedel <joro@8bytes.org> wrote:
> > Hi,
> >
> > here is the second version of my PTI implementation for
> > x86_32, based on tip/x86-pti-for-linus. It took a lot longer
> > than I had hoped, but there have been a number of obstacles
> > on the way. It also isn't the small patch-set anymore that v1
> > was, but compared to it this one actually works :)
>
> One thing worth noting is that performance of this whole series is
> going to be abysmal due to the complete lack of 32-bit PCID. Maybe
> any kernel built with this option set that runs on a CPU that has
>the

What kind of slowdown are we talking about here?

> PCID bit set in CPUID should print a big fat warning like "WARNING:
> you are using 32-bit PTI on a 64-bit PCID-capable CPU. Your
> performance will increase dramatically if you switch to a 64-bit
> kernel."

Hardware supports PCID even on 32-bit kernels, no?

Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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