Re: [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support

[Florian Weimer]

On 09/14/2018 03:05 PM, Thomas Gleixner wrote:
> On Fri, 14 Sep 2018, Florian Weimer wrote:
>
> > On 09/14/2018 02:50 PM, Thomas Gleixner wrote:
> > > Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime()
> > > implementation, which extended the clockid switch case and added yet
> > > another slightly different copy of the same code.
> > >
> > > Especially the extended switch case is problematic as the compiler tends to
> > > generate a jump table which then requires to use retpolines.
> >
> > Does vDSO code really have to use retpolines?  It's in userspace, after all.
>
> Unless you have IBRS/STIPB enabled, you need user space ratpoutine as well.

I don't think this is a consensus position, and it obviously depends on 
the (sub)architecture.

Thanks,
Florian