On Wed, Nov 28, 2018 at 10:35:51AM +0100, Greg Kurz wrote: > On Wed, 28 Nov 2018 13:57:14 +1100 > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > On Fri, Nov 16, 2018 at 11:57:05AM +0100, Cédric Le Goater wrote: > > > We will need to use xics_max_server_number() to create the sPAPRXive > > > object modeling the interrupt controller of the machine which is > > > created before the CPUs. > > > > > > Signed-off-by: Cédric Le Goater <c...@kaod.org> > > > > My only concern here is that this moves the spapr_set_vsmt_mode() > > before some of the sanity checks in spapr_init_cpus(). Are we certain > > there are no edge cases that could cause badness? > > > > The early checks in spapr_init_cpus() filter out topologies that would > result in partially filled cores. They're only related to the rest of > the code that creates the boot CPUs. Before commit 1a5008fc17, > spapr_set_vsmt_mode() was even being called before spapr_init_cpus(). > The rationale to move it there was to ensure it is called before the > first user of spapr->vsmt, which happens to be a call to > xics_max_server_number().
Ok.
> Now that xics_max_server_number() needs to be called even earlier, I think a
> better change is to have xics_max_server_number() to call
> spapr_set_vsmt_mode()
> if spapr->vsmt isn't set.
I'd rather not do that, but instead move it statically to where it
needs to be. That sort of lazy/on-demand initialization can result in
really confusing behaviours depending on when a seemingly innocuous
data-returning function is called, so I consider it a code smell.
>
> > > ---
> > > hw/ppc/spapr.c | 10 +++++-----
> > > 1 file changed, 5 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index 7afd1a175bf2..50cb9f9f4a02 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -2466,11 +2466,6 @@ static void spapr_init_cpus(sPAPRMachineState
> > > *spapr)
> > > boot_cores_nr = possible_cpus->len;
> > > }
> > >
> > > - /* VSMT must be set in order to be able to compute VCPU ids, ie to
> > > - * call xics_max_server_number() or spapr_vcpu_id().
> > > - */
> > > - spapr_set_vsmt_mode(spapr, &error_fatal);
> > > -
> > > if (smc->pre_2_10_has_unused_icps) {
> > > int i;
> > >
> > > @@ -2593,6 +2588,11 @@ static void spapr_machine_init(MachineState
> > > *machine)
> > > /* Setup a load limit for the ramdisk leaving room for SLOF and FDT
> > > */
> > > load_limit = MIN(spapr->rma_size, RTAS_MAX_ADDR) - FW_OVERHEAD;
> > >
> > > + /* VSMT must be set in order to be able to compute VCPU ids, ie to
> > > + * call xics_max_server_number() or spapr_vcpu_id().
> > > + */
> > > + spapr_set_vsmt_mode(spapr, &error_fatal);
> > > +
> > > /* Set up Interrupt Controller before we create the VCPUs */
> > > smc->irq->init(spapr, &error_fatal);
> > >
> >
>
--
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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