[linux-yocto] v5.2.x - stable updates comprising v5.2.23

[Paul Gortmaker]

Bruce, Yocto kernel folks:

Here is the next 5.2.x stable update "extension" primarily created for
the Yocto project, continuing from the first v5.2.22 post-EOL release.

This 5.2.22 release only contains about 22 mainline commits.  Rather
than continue the audit of what went into 5.3.8 - I jumped ahead to
5.3.11 in order to get the latest CVE embargo commits relating to
iTLB/tsx/TAA, as I assumed they would be of interest to people.

Folks will find in /sys/devices/system/cpu/vulnerabilities - alongside
spectre and meltdown, new files itlb_multihit and tsx_async_abort, and
can look them up in the documentation for more details.

I will circle back to 5.3.8+ content for the next v5.2.24 release I'll
be starting shortly.

The CVE was significant to KVM, and as such, the commits had a fairly
high footprint in that subsystem.  I used a code refactoring mainline
commit from between 5.2 and 5.3 in order to enable using the CVE related
KVM commits with as little alteration as possible.  Also possibly worth
a mention, is that post-5.2 the main kvm_lock went from being a spinlock
to a mutex.  Rather than risk any possible impact to -rt, I simply
retained it being a spin, and adjusted the CVE commits accordingly.

I've put this 5.2.23 queue through the usual testing; build testing on
x86-64/32, ARM-64/32, PPC and MIPS, plus some static analysis and
finally some sanity runtime tests on x86-64.

In addition, since there was a significant KVM footprint in the
changelog, I also built a defconfig with KVM and KVM_INTEL enabled, and
booted that same kernel as host and guest, on both kvm-intel enabled and
older non-kvm-intel enabled systems, and saw no obvious issues.

I did the signed tag just as per the previously released versions.
Please find a signed v5.2.23 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/pub/scm/linux/kernel/git/paulg/linux-5.2.y.git/?h=linux-5.2.y
  git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux-5.2.y.git

for merge to standard/base in linux-yocto-5.2 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-5.2.git/

This repo isn't needed for anything; it just exists for transparency and
so people can see the evolution of the raw commits that were originally
selected to create this 5.2.x release.

Paul.