Comment 5 for bug 1867717

It seems the email reply didn't work, so pasting here again (sorry if it yields a duplication later):

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Hi Seth,

Well, it's a mess and confusing...

PowerVM doesn't share the same code base as KVM, so the bug doesn't affect PowerVM, so it's KVM-specific.

POWER8 has TM supported both on baremetal (PowerNV or powernv) and on KVM guests.
The fix involves a hypercall implemented by the KVM, so it affects the POWER8 hosts running a KVM guest. In that case it's like the guest is attacking the host and its (guest's kernel) kernel version is no relevant to reproduce the issue.

POWER9 doesn't support TM on baremetal, only on KVM guests, but TM is software assisted (due to a bug in the chip - that's the reason on the other hand why it's not supported on baremetal, only on guests), so the code path on the host when P9 guests use TM is a bit different.
But I haven't gone so far to able to explain why it doesn't affect P9 hosts, but it's probably be cause of the software assisted part. So, P9 hosts are not affected.

So, summing it up, it affects only POWER8 + KVM running Bionic 4.15 kernels.

BTW, I would be glad if credit could be attributed to me when filling up the CVE details, when applicable :)

Kind regards,
Gustavo