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Re: [Qemu-ppc] [PULL 11/18] pseries: Split CAS PVR negotiation out into
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [PULL 11/18] pseries: Split CAS PVR negotiation out into a separate function |
Date: |
Wed, 31 May 2017 16:33:21 +1000 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Mon, May 29, 2017 at 11:14:08PM +0200, Greg Kurz wrote:
> On Thu, 25 May 2017 13:51:25 +1000
> David Gibson <address@hidden> wrote:
>
> > Guests of the qemu machine type go through a feature negotiation process
> > known as "client architecture support" (CAS) during early boot. This does
> > a number of things, one of which is finding a CPU compatibility mode which
> > can be supported by both guest and host.
> >
> > In fact the CPU negotiation is probably the single most complex part of the
> > CAS process, so this splits it out into a helper function. We've recently
> > made some mistakes in maintaining backward compatibility for old machine
> > types here. Splitting this out will also make it easier to fix this.
> >
> > This also adds a possibly useful error message if the negotiation fails
> > (i.e. if there isn't a CPU mode that's suitable for both guest and host).
> >
> > Signed-off-by: David Gibson <address@hidden>
> > Reviewed-by: Laurent Vivier <address@hidden>
> > Reviewed-by: Greg Kurz <address@hidden>
> > ---
>
> Any reason for not seing these patches as well in this pull request ?
>
> pseries: Restore PVR negotiation logic for pre-2.9 machine types
> pseries: Improve tracing of CPU compatibility negotiation
Yes. After more discussion; and comparison with analogous x86 cases
that came up with Igor's NUMA cleanups, I've decided that the
behaviour here while guest visible comes under the heading of a
firmware behaviour change, which we don't typically arrange 100%
matching behaviour for. Meanwhile, I also found out more things that
suggest matching old behaviour correctly is going to be even messier
than I though.
So, I've decided that leaving the behaviour change in place is the
better course. Note that it won't affect migration (at least after
the other compat/migration fixes are merged).
I'll reconsider if we observe a real problem in the wild with it.
--
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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- [Qemu-ppc] [PULL 02/18] ppc/xics: simplify prototype of xics_spapr_init(), (continued)
- [Qemu-ppc] [PULL 02/18] ppc/xics: simplify prototype of xics_spapr_init(), David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 04/18] spapr-cpu-core: release ICP object when realization fails, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 10/18] spapr: fix error reporting in xics_system_init(), David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 08/18] hw/ppc/spapr_events.c: removing 'exception' from sPAPREventLogEntry, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 07/18] spapr: ensure core_slot isn't NULL in spapr_core_unplug(), David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 09/18] spapr_cpu_core: drop reference on ICP object during CPU realization, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 06/18] xics_kvm: cache already enabled vCPU ids, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 13/18] spapr: add pre_plug function for memory, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 11/18] pseries: Split CAS PVR negotiation out into a separate function, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 14/18] hw/ppc/spapr.c: adding pending_dimm_unplugs to sPAPRMachineState, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 03/18] spapr: sanitize error handling in spapr_ics_create(), David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 05/18] spapr: Consolidate HPT freeing code into a routine, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 18/18] xics: add unrealize handler, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 15/18] hw/ppc: removing drc->detach_cb and drc->detach_cb_opaque, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 12/18] pseries: Restore support for total vcpus not a multiple of threads-per-core for old machine types, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 17/18] hw/ppc/spapr.c: recover pending LMB unplug info in spapr_lmb_release, David Gibson, 2017/05/24
- [Qemu-ppc] [PULL 16/18] hw/ppc: migrating the DRC state of hotplugged devices, David Gibson, 2017/05/24
- Re: [Qemu-ppc] [Qemu-devel] [PULL 00/18] ppc-for-2.10 queue 20170525, Stefan Hajnoczi, 2017/05/30