> > I wonder, what is the benefit of this then.
> > If users need to change the machine type, then they can just as well set
> the
> > CFPC/SBBC/IBS caps right?
> I believe the issue is similar to what we initially hit with:
> Bug 165081 - LP1752026- Ubuntu18.04:POWER9:DD2.2: Unable to start a KVM
> guest with default machine type(pseries-bionic) complaining "KVM
> implementation does not support Transactional Memory, try cap-htm=off"
> (kvm)
> where due to lack of "-machine pseries-*,cap-*=on/off/*" support via
> libvirt we need to rely on machine type behavior to enable certain
> options in the interim.

Yes exactly.

And this is why I was asking for more guidance on the preferred defaults,
as the addition of an extra type still needs the user to do something (e.g.
selecting that type).


> IFF there are changes to 2.12 in the remaining upstream 2.12 or the coming
> > Ubuntu 18.10 development cycle we will not try (too hard) to keep e.g. a
> > Bionic pseries-2.12-sxxm in sync with that of 18.10.
> Doesn't seem likely to change at this point but that seems reasonable
> either way.

Yeah, as much as upstream can't change 2.11 anymore (which is why you make
it a 2.12 type) we can't change 2.12 yet (in this release).


> Same (=please let me know asap) is true if instead you want any of:
> > pseries-2.11-sxxm
> > pseries-bionic-sxxm
> Adding pseries-2.11-sxxm/pseries-bionic-sxxm gives us some flexibility
> with different firmware/hardware and migration strategies so this would
> be our preference.

Ok, will do so.
We will keep the 2.12 type as-is in code, but it might change (if it
changes upstream - unlikely).
While together we will try to keep the bionic types stable.

> This is also in line with how things are done with
> spectre-related CPU capabilities in 2.12/2.11.1 for x86 (new explicit
> cpu types as opposed to changed defaults).

Yes, that is true on x86

> In terms of upstream patches that need to be backported I think we also
> want "ppc/spapr-caps: Disallow setting workaround for spapr-cap-ibs". I
> got a pretty clean backport on top of 2.11.1 just cherry-picking:

I already have this patch in my current build - I added it to the
description here when I was dupping the other bug onto this.

> ppc/spapr-caps: Define the pseries-2.12-sxxm machine type
> ppc/spapr-caps: Convert cap-ibs to custom spapr-cap
> ppc/spapr-caps: Disallow setting workaround for spapr-cap-ibs
> ppc/spapr-caps: Convert cap-sbbc to custom spapr-cap
> ppc/spapr-caps: Convert cap-cfpc to custom spapr-cap
> ppc/spapr-caps: Add support for custom spapr_capabilities
> target/ppc: Check mask when setting cap_ppc_safe_indirect_branch

That is exactly the series I already have in my ppa since yesterday

> Then an ubuntu-specific pseries-2.11-sxxm patch would basically mirror
> the "ppc/spapr-caps: Define the pseries-2.12-sxxm machine type"
> implementation and pseries-bionic-sxxm could point to that.

Exactly my thought will do so and respin the build in the ppa.

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  backport needed for spectre/meltdown mitigation machine type qemu
  patches (kvm)

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