Comment 4 for bug 1752026

For 1. I mostly agree, the default is currently off in code and in 2.11 there is this for backwards compatability:
  smc->default_caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_ON;

We would have to
- Moving that "keep the old default" entry to 2.10 (to cover <=2.10)
  spapr_machine_2_10_class_options
   smc->default_caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_ON;
- And we would set it explicit off in 2.11 (which is what pseries-bionic refers to)
  spapr_machine_2_11_class_options
   smc->default_caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_OFF;
- 2.12 we would not change IMHO, that might become whatever it becomes with 2.12 development

For #2 - this is a bug fix so it does not fall under the Feature Freeze (tomorrow).
But I don't know how much lead time the kernel team needs.
Given that kernel fixes are involved this clearly needs a kernel task for them to know about - adding ...

@Kernel - please read the context - what is the last date you'd need to have this commit upstream by IBM to be able to pick it and still be in the initial 18.04 release kernel (not in -updates)?

@IBM - how about this approach:
A) We switch the default to HTM=off in qemu "now" (as soon as you ack this) to be safe
B) If you get the kernel fixes upstream fast enough for the kernel Team to pick up in time:
  B1) a fixed kernel will be pushed (before 18.04 release)
  B2) we unroll this change in qemu (before 18.04 release)

That way we would surely have something that "works" by default via (A) and if (B) is in time we can switch back to "working but with HTM enabled".
And if (B) is too late we will keep HTM disabled in the 2.11/Bionic machine type.