Re: [RESEND] Spectre-v2 (IBPB/IBRS) and SSBD fixes for 4.4.y

["Srivatsa S. Bhat" <srivatsa@csail.mit.edu>]

On 7/23/18 3:06 PM, Jiri Kosina wrote:
> On Sat, 14 Jul 2018, Srivatsa S. Bhat wrote:
> 
>> This patch series is a backport of the Spectre-v2 fixes (IBPB/IBRS)
>> and patches for the Speculative Store Bypass vulnerability to 4.4.y
>> (they apply cleanly on top of 4.4.140).
> 
> FWIW -- not sure how much inspiration you took from our SLE 4.4-based 
> tree, but most of the stuff is already there for quite some time 
> (including the non-upstream IBRS on kernel boundary on SKL+, trampoline 
> stack for PTI (which the original port didn't have), etc).
> 
> The IBRS SKL+ stuff has not been picked up by Greg, as it's non-upstream, 
> and the trampoline stack I believe was pointed out to stable@, but noone 
> really sat down and did the port (our codebase is different than 4.4.x 
> stable base), but it definitely should be done if someone has to put 100% 
> trust into the PTI port (either that, or at least zeroing out the kernel 
> thread thread stack ... we used to have temporarily that before we 
> switched over to proper entry trampoline in this version as well).
> 

I did glance at the SLES 4.4 kernel sometime ago, but there seemed to
be way too many custom patches and I wasn't sure in what ways your
PTI/Spectre fixes depended on the other (x86) patches in your tree. So
I decided to backport entirely from the 4.9 stable tree instead. My
reasoning was that, since the 4.9 stable patches were trusted to work
well, their 4.4 backports should work well too, as long as they are
backported correctly.
 
However, if you are proposing that you'd like to contribute the
enhanced PTI/Spectre (upstream) patches from the SLES 4.4 tree to 4.4
stable, and have them merged instead of this patch series, then I
would certainly welcome it!

Regards,
Srivatsa
VMware Photon OS