Re: Intel microcode update and glibc HLE

["Carlos O'Donell" <carlos@redhat.com>]

On 09/26/2014 02:54 PM, Siddhesh Poyarekar wrote:
>> I'll be updating the Fedora kernel and dracut to do early microcode
>> loading today.  Kyle McMartin looked at the suspend/hibernate-resume
>> paths and things should work fine with early microcode loading.
> 
> That's great.

I agree, that is great news.
 
>> Disabling this in glibc on x86 seems fine since nothing will be
>> capable of using it until newer CPUs are released, but it wasn't
>> strictly necessary.
> 
> I wasn't aware of the plan to do the early microcode loading, which is
> why we went with disabling HLE.  It's really just a flip of a
> configure flag and rebuild, so we can even revert it and test once the
> kernel bits are in.

It turns out to be more than just a configure flag.

Andi's recent rwlock changes use TSX unconditionally.

I've raised this issue with Andi to see if we can put it all under the
same configure flag.

Similarly for ppc64 and s390 I think I'll make the flag do this:

--enable-lock-elision=yes (enable for all machines)
--enable-lock-elisoin=x86_64,ppc64,s390x (enable for these machines)
--enable-lock-elision-no (disable for all machines)

Cheers,
Carlos.