[PULL][SRU Zesty] Fix KVM hang on ThunderX systems

dann frazier dann.frazier at canonical.com
Thu Aug 3 19:28:50 UTC 2017

Here's a backport of the KVM hang fix for ThunderX systems for zesty.

BugLink: https://bugs.launchpad.net/bugs/1673564

Here's the description, cut & pasted from my earlier artful PR:
There's a pretty nasty errata for ThunderX SoCs in which a guest can
cause interrupts to be disabled on the host kernel. The symptoms vary,
but it's easy to reproduce running a bunch of parallel VM start/stop

There was quite a bit of backporting required for the patches in this
series. For such patches, I've described the changes required in a
comment above my S-o-B. They are mostly mechanical transformations to
revert macro cleanups that occurred post-4.11.

I've previously submitted versions for unstable[*] and artful[**]. I
mentioned in the artful PR that, while my artful backport applied
cleanly to zesty, I was seeing crashes there. Using bisection, I found
this to be resolved by a v4.11 patch that disables stack-protector
when compiling EL2 code on arm64. That patch is included in this
series. Note: there's also an arm32 patch for this that I did *not*
include, because I don't have a way to test it. However, it is tagged
for stable, so you might want to consider pulling it as well:

  501ad27c arm: KVM: Do not use stack-protector to compile HYP code

I've had this running my reproducer for several hours on 2 systems - a
ThunderX system, which requires this workaround, and a Qualcomm
QDF2400 system that does not, with no issues.

[*] https://lists.ubuntu.com/archives/kernel-team/2017-July/085587.html
[**] https://lists.ubuntu.com/archives/kernel-team/2017-July/085810.html

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