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Re: Better communication about spectre/meltdown



On Sat, 2018-03-03 at 10:18 -0500, Roberto C. Sánchez wrote:
> On Sat, Mar 03, 2018 at 02:31:20PM +0000, Ben Hutchings wrote:
> > On Thu, 2018-03-01 at 07:56 -0500, Roberto C. Sánchez wrote:
> > 
> > > Of course, if this looks like it would be substantially more complex, I
> > > will again ask for guidance, but the likely course at that point seems
> > > to implement the necessary option parsing in gcc 4.6.
> > > 
> > > I suppose another possibility would be to backport the patches to gcc
> > > 4.7 instead of 4.6 and switch the kernel build to gcc 4.7. Would that be
> > > considered to introduce less risk than bringing gcc 4.9 into wheezy at
> > > this stage?
> > 
> > Unless you're experienced in gcc development, I would guess that using
> > the existing patches for gcc 4.9 is lower risk.
> > 
> 
> Your meaning here is not clear to me. I am not experienced in gcc
> development and I have observed that the code is exceptionally complex.
> That is why I want to make sure to ask for and receive guidance from
> those who are more experienced in this area.
> 
> Do you mean to say that applying the gcc 4.9 patches to gcc 4.7 in
> wheezy is the lower risk approach, or that backporting gcc 4.9 to wheezy
> is lower risk?

I think that backporting gcc-4.9 and building the kernel with it (for
x86) is lower risk than backporting the retpoline patches to gcc-4.7
and building the kernel with that.  (In fact it's not just the kernel;
if you change gcc-4.7 that has the potential to affect most updates to
wheezy, even though use of retpoline should be disabled by defaul.)

Ben.

-- 
Ben Hutchings
[W]e found...that it wasn't as easy to get programs right as we had
thought. ... I realized that a large part of my life from then on was
going to be spent in finding mistakes in my own programs. - Maurice
Wilkes, 1949

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