Code review comment for ~rafaeldtinoco/ubuntu/+source/qemu:lp1828495-disco-devel-qemu

Based on public bug feedback from Intel, looks like I've missed the undocumented MDS-NO mitigation bit from ARCH_CAPABILITIES. I haven't done it because last manual from Intel does not show it, I'm really not sure where to find more documentation about it.. but its a simple upstream change (just the MSR flag) so I backported and I'm pushing the change here.

I'm first dealing with the Bionic SRU, and if it is all good, I'll include the same patch in this change.

Comments from the Bionic merge request:

https://code.launchpad.net/~rafaeldtinoco/ubuntu/+source/qemu/+git/qemu/+merge/368804/comments/969879
https://code.launchpad.net/~rafaeldtinoco/ubuntu/+source/qemu/+git/qemu/+merge/368804/comments/969880

From the other merge request:

"""
This is the upstream change:

https://github.com/qemu/qemu/commit/20140a82c674

This is the public comment from Intel:

https://bugs.launchpad.net/intel/+bug/1828495/comments/40

And commit the patch is:

    - 0017-target-i386-add-MDS-NO-feature.patch (LP: #1828495):
      target/i386: add MDS-NO feature
      (upstream: 20140a82c674, desc: v4.0.0-721-g20140a82c6)
"""