[linux-yocto] v4.12.x - stable updates comprising v4.12.21

[Paul Gortmaker]

Bruce, Yocto kernel folks:

Here is another 4.12.x stable update "extension" primarily created for
the Yocto project, continuing on top of the previous v4.12.20 kernel.

There about 90 commits here, with the main thing being addition of the
mainline retpoline commits based on what was used for 4.14-stable.
There is also now the /sys/devices/system/cpu/vulnerabilities dir that
I suspect people will be looking for.

As usual, I've put this 4.12.x queue through the various testing that I
figured made sense, which includes but is not limited to:

-x86-64 sanity boot test + workloads of defconfig on COTS Core2 box.
-build MIPS, PPC, ARM, ARM64 with defconfig
-build x86-64 allmodconfig/allyesconfig
-build i386 allmodconfig/allyesconfig
-test x86-64 with preempt-rt patches.

I bumped the 4.12 Makefile and did the signed tag just as per the previously
released 4.12.x versions.

Please find a signed v4.12.21 tag using this key:

http://pgp.mit.edu/pks/lookup?op=vindex&search=0xEBCE84042C07D1D6

in the repo in the kernel.org directory here:

   https://git.kernel.org/cgit/linux/kernel/git/paulg/linux-4.12.y.git/
   git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux-4.12.y.git

for merge to standard/base in linux-yocto-4.12 and then out from there
into the other base and BSP branches.

For those who are interested, the evolution of the commits is here:

   https://git.kernel.org/cgit/linux/kernel/git/paulg/longterm-queue-4.12.git/

This repo isn't needed for anything; it just exists for transparency and
so people can see the raw commits that were used to create this 4.12.x
release, similar to Greg's stable queue:

   https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/

Paul.
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