* Michael Roth (mdr...@linux.vnet.ibm.com) wrote: > Quoting David Gibson (2018-07-17 05:50:06) > > On Thu, Jun 21, 2018 at 03:23:21PM +0200, Greg Kurz wrote: > > > On Thu, 21 Jun 2018 11:18:09 +1000 > > > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > > > > > On Wed, Jun 20, 2018 at 02:54:15PM +0200, Greg Kurz wrote: > > > > > The spapr capability framework was introduced in QEMU 2.12. It allows > > > > > to have an explicit control on how host features are exposed to the > > > > > guest. This is especially needed to handle migration between hetero- > > > > > geneous hosts (eg, POWER8 to POWER9). It is also used to expose fixes/ > > > > > workarounds against speculative execution vulnerabilities to guests. > > > > > The framework was hence backported to QEMU 2.11.1, especially these > > > > > commits: > > > > > > > > > > 0fac4aa93074 spapr: Add pseries-2.12 machine type > > > > > 9070f408f491 spapr: Treat Hardware Transactional Memory (HTM) as an > > > > > optional capability > > > > > > > > > > 0fac4aa93074 has the confusing effect of making pseries-2.12 the > > > > > default > > > > > machine type for QEMU 2.11.1, instead of the expected pseries-2.11. > > > > > This > > > > > patch changes the default machine back to pseries-2.11. > > > > > > > > > > Unfortunately, 9070f408f491 enforces the HTM capability for > > > > > pseries-2.11 > > > > > to be enabled by default, ie, when not passing cap-htm on the command > > > > > line. This breaks several 'make check' testcases that run > > > > > qemu-system-ppc64 > > > > > with TCG. > > > > > > > > > > The only sane way to fix this is to adapt the impacted testcases so > > > > > that > > > > > they all pass cap-htm=off in this case. This patch does that as well. > > > > > > > > > > Signed-off-by: Greg Kurz <gr...@kaod.org> > > > > > --- > > > > > v2: - have the testcases to pass cap-htm=off instead of violating the > > > > > capabilities logic. > > > > > > > > > > Upstream doesn't need anything like that since newer pseries machine > > > > > types > > > > > start with HTM disabled by default. This is really a oneshot fix for > > > > > 2.11.2, > > > > > and I've tried to make it as small as possible. > > > > > > > > > > This is a full replacement of the previous version. It is based on > > > > > Mike's > > > > > staging tree for 2.11: > > > > > > > > Thanks for fixing this up > > > > > > > > Reviewed-by: David Gibson <da...@gibson.dropbear.id.au> > > > > > > > > Btw, 2.11.z should probably have the 2.12 machine type removed > > > > entirely, as well as (obviously) not being the default. Not within > > > > scope for this patch, though. > > > > > > > > > > Well... it is indeed weird but I don't think it hurts. Also, people > > > may have started using pseries-2.12 with QEMU 2.11.1 (I seem to > > > remember Mike told me about something like this the other day)... > > > > I came back to thinking about this and realized this is a terrible > > idea. The problem is that because of the way we define the latest > > machine type, then backwards compat props for the earlier ones, it's > > very likely that the "pseries-2.12" in 2.11 won't be the same as > > pseries-2.12 in 2.12, simply because 2.11 won't have the necessary > > features to implement pseries-2.12 as in 2.12. > > What I saw was likely a holdover from early Ubuntu 18.04 p9 testing > before HTM emulation had made it's way into their kernel. In that > particular case Ubuntu doesn't support it at all now, but it remains > the only option for anyone else who happens to find themselves in > that situation and doesn't have a libvirt/Openstack with appropriate > machine capabilities. > > Given that it was at least possible to run that config (however > broken) with QEMU 2.11.0, it seemed fair to leave some sort of > "out". But really it just seems like we don't have much to gain > by removing it at this point.
It may confuse people trying to migrate from 2.11.1 to 2.12 Dave > I agree in general though and probably would've handled this > differently if I'd thought through it a bit more. > > > > > > > -- > > David Gibson | I'll have my music baroque, and my code > > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > > | _way_ _around_! > > http://www.ozlabs.org/~dgibson > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK