RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

[Lu, Hongjiu]

> 
> On Mon, 2018-01-08 at 18:42 +0100, Peter Zijlstra wrote:
> > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote:
> > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote:
> > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote:
> > > >>> a good suggestion, but we encountered some issues with it either
> > > >>> crashing the kernel at boot or not properly turning on/off.
> > > >
> > > > The below boots, but I lack stuff to test the enabling.
> > >
> > > Peter,
> > >
> > > Thanks. Will give it a spin. One other concern is if JUMP_LABEL is
> > > not configured, this may not work, and we may still need fall back
> > > to a control variable.
> >
> > Urgh yes.. I always forget about that case. Will the retpoline crud be
> > backported to a GCC old enough to not have asm-goto? If not, we could
> > make all of this simply require asm-goto.
> 
> I think HJ said he was planning to backport as far as 4.9. When was asm-
> goto added?

It was added to GCC 4.5.

H.J.