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. -- 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
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