Re: [PLUG] The mysterious case of the Linux Page Table Isolation patches

[Steve Litt <slitt@troubleshooters.com>]

On Thu, 4 Jan 2018 15:09:31 -0500
Rich Freeman <r-plug@thefreemanclan.net> wrote:

> On Thu, Jan 4, 2018 at 2:34 PM, Steve Litt
> <slitt@troubleshooters.com> wrote:
> >
> > According to
> > https://www.phoronix.com/scan.php?page=news_item&px=x86-PTI-EPYC-Linux-4.15-Test  ,
> > the latest kernel updates enable PTI on AMD "just in case", but
> > because AMD is so confident it's not needed, PTI will again be
> > disabled in 4.15. For those wanting to repeal the performance hit
> > on their AMD earlier, they can put "nopti" in their grub.
> >  
> 
> Correct.  It is in the queue for 4.14.12 as well, and presumably all
> the other stable/longterm kernels.  I hear Arch backported it to
> 4.14.11, and I imagine many other distros will do so as well since it
> was accepted upstream.

Thanks for all your help, Rich (and everyone else). After updating, I
rebooted to 4.14.11, and I appear to be protected...

============================================
[slitt@mydesk ~]$ uname -a
Linux mydesk 4.14.11_1 #1 SMP PREEMPT Wed Jan 3 16:59:01 UTC 2018
x86_64 GNU/Linux [slitt@mydesk ~]$
============================================

============================================
[slitt@mydesk ~]$ cat /proc/cpuinfo | grep secure
bugs		: fxsave_leak sysret_ss_attrs null_seg cpu_insecure
bugs		: fxsave_leak sysret_ss_attrs null_seg cpu_insecure
[slitt@mydesk ~]$
============================================

So far I'm not seeing a performance hit meaningul to my workflow, so
I'll leave well enough alone and figure that sooner or later another
update will make my AMD run as fast as it can run securely.

Thanks for all your help.
 
SteveT

Steve Litt 
December 2017 featured book: Thriving in Tough Times
http://www.troubleshooters.com/thrive
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