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Re: [Qemu-ppc] [PATCH v2 4/7] ppc: open code cpu creation for machine ty
From: |
Greg Kurz |
Subject: |
Re: [Qemu-ppc] [PATCH v2 4/7] ppc: open code cpu creation for machine types |
Date: |
Mon, 4 Jul 2016 10:08:53 +0200 |
On Mon, 4 Jul 2016 08:32:04 +0200
Greg Kurz <address@hidden> wrote:
> On Mon, 4 Jul 2016 13:54:55 +1000
> David Gibson <address@hidden> wrote:
>
> > On Sat, Jul 02, 2016 at 10:33:33AM +0200, Greg Kurz wrote:
> > > On Sat, 2 Jul 2016 13:36:22 +0530
> > > Bharata B Rao <address@hidden> wrote:
> > >
> > > > On Sat, Jul 02, 2016 at 12:41:48AM +0200, Greg Kurz wrote:
> > > > > If we want to generate cpu_dt_id in the machine code, this must occur
> > > > > before the cpu gets realized. We must open code the cpu creation to be
> > > > > able to do this.
> > > > >
> > > > > This patch just does that. It borrows some lines from previous work
> > > > > from Bharata to handle the feature parsing.
> > > > >
> > > > > Signed-off-by: Greg Kurz <address@hidden>
> > > > > ---
> > > > > hw/ppc/ppc.c | 39 ++++++++++++++++++++++++++++++++++++++-
> > > > > 1 file changed, 38 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
> > > > > index dc3d214009c5..57f4ddd073d0 100644
> > > > > --- a/hw/ppc/ppc.c
> > > > > +++ b/hw/ppc/ppc.c
> > > > > @@ -32,6 +32,7 @@
> > > > > #include "sysemu/cpus.h"
> > > > > #include "hw/timer/m48t59.h"
> > > > > #include "qemu/log.h"
> > > > > +#include "qapi/error.h"
> > > > > #include "qemu/error-report.h"
> > > > > #include "hw/loader.h"
> > > > > #include "sysemu/kvm.h"
> > > > > @@ -1353,5 +1354,41 @@ PowerPCCPU *ppc_get_vcpu_by_dt_id(int
> > > > > cpu_dt_id)
> > > > >
> > > > > PowerPCCPU *ppc_cpu_init(const char *cpu_model)
> > > > > {
> > > > > - return POWERPC_CPU(cpu_generic_init(TYPE_POWERPC_CPU,
> > > > > cpu_model));
> > > > > + PowerPCCPU *cpu;
> > > > > + CPUClass *cc;
> > > > > + ObjectClass *oc;
> > > > > + gchar **model_pieces;
> > > > > + Error *err = NULL;
> > > > > +
> > > > > + model_pieces = g_strsplit(cpu_model, ",", 2);
> > > > > + if (!model_pieces[0]) {
> > > > > + error_report("Invalid/empty CPU model name");
> > > > > + return NULL;
> > > > > + }
> > > > > +
> > > > > + oc = cpu_class_by_name(TYPE_POWERPC_CPU, model_pieces[0]);
> > > > > + if (oc == NULL) {
> > > > > + error_report("Unable to find CPU definition: %s",
> > > > > model_pieces[0]);
> > > > > + return NULL;
> > > > > + }
> > > > > +
> > > > > + cpu = POWERPC_CPU(object_new(object_class_get_name(oc)));
> > > > > +
> > > > > + cc = CPU_CLASS(oc);
> > > > > + cc->parse_features(CPU(cpu), model_pieces[1], &err);
> > > >
> > > > Igor is working on a patchset to convert -cpu features into global
> > > > properties.
> > > > IIUC, after that patchset, it is not recommended to parse the -cpu
> > > > features
> > > > for every CPU but do it only once.
> > > >
> > >
> > > cpu_generic_init() in the current code also does the parsing, and as the
> > > title
> > > says, this patch is just about open coding the creation. I don't want to
> > > change behavior yet.
> > >
> > > But yes, I agree that we should only parse features once and I'll be more
> > > than
> > > happy to fix this in a followup patch, based on Igor's work.
> > >
> > > In the meantime, maybe I can add a comment stating that the parsing
> > > should go
> > > away ?
> >
> > Right. But the thing is by open coding here, you're making two copies
> > that need to be fixed instead of one, which increases the chances of
> > error.
> >
> > It seems like it would be safer to change the generic code so there's
> > a new generic function which doesn't do the realize which we can use
> > on ppc (and other platforms when/if they need it).
> >
> > Doing the change just on ppc by making our own copy of
> > cpu_generic_init() seems more like to lead to future mistakes.
> >
>
> I had this in v1:
>
> http://patchwork.ozlabs.org/patch/642216/
>
> I'll repost it in v3.
>
I tend to agree with Igor's latest feeback:
https://lists.nongnu.org/archive/html/qemu-devel/2016-07/msg00381.html
I'll keep the open coded version in v3.
> > > > That is what I attempted here in the context of supporting compat cpu
> > > > type
> > > > for pseries-2.7:
> > > >
> > > > https://www.mail-archive.com/address@hidden/msg381660.html
> > > >
> > >
> > > Yeah and this is where I borrowed some lines. :)
> > >
> > > > Regards,
> > > > Bharata.
> > > >
> > >
> > > Cheers.
> > >
> >
>
pgpj5Ly_dKwaM.pgp
Description: OpenPGP digital signature
- [Qemu-ppc] [PATCH v2 2/7] ppc: simplify max_smt initialization in ppc_cpu_realizefn(), (continued)
[Qemu-ppc] [PATCH v2 5/7] ppc: introduce ppc_set_vcpu_dt_id(), Greg Kurz, 2016/07/01
[Qemu-ppc] [PATCH v2 6/7] spapr: use ppc_set_vcpu_dt_id() in CPU hotplug code, Greg Kurz, 2016/07/01
[Qemu-ppc] [PATCH v2 7/7] ppc: move the cpu_dt_id logic to machine code, Greg Kurz, 2016/07/01
Re: [Qemu-ppc] [PATCH v2 0/7] ppc: compute cpu_dt_id in the machine code, Bharata B Rao, 2016/07/02