Re: [PATCH v6 17/18] spapr: Clean up RMA size calculation

[David Gibson]

On Tue, Feb 25, 2020 at 12:07:29PM +0100, Philippe Mathieu-Daudé wrote:
> On 2/25/20 12:37 AM, David Gibson wrote:
> > Move the calculation of the Real Mode Area (RMA) size into a helper
> > function.  While we're there clean it up and correct it in a few ways:
> >    * Add comments making it clearer where the various constraints come from
> >    * Remove a pointless check that the RMA fits within Node 0 (we've just
> >      clamped it so that it does)
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >   hw/ppc/spapr.c | 59 ++++++++++++++++++++++++++++++--------------------
> >   1 file changed, 35 insertions(+), 24 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 6e9f15f64d..f0354b699d 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2648,6 +2648,40 @@ static PCIHostState *spapr_create_default_phb(void)
> >       return PCI_HOST_BRIDGE(dev);
> >   }
> > +static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
> > +{
> > +    MachineState *machine = MACHINE(spapr);
> > +    hwaddr rma_size = machine->ram_size;
> > +    hwaddr node0_size = spapr_node0_size(machine);
> > +
> > +    /* RMA has to fit in the first NUMA node */
> > +    rma_size = MIN(rma_size, node0_size);
> > +
> > +    /*
> > +     * VRMA access is via a special 1TiB SLB mapping, so the RMA can
> > +     * never exceed that
> > +     */
> > +    rma_size = MIN(rma_size, TiB);
> 
> Can you use '1 * TiB'? It makes review obvious.

Done.

> > +
> > +    /*
> > +     * Clamp the RMA size based on machine type.  This is for
> > +     * migration compatibility with older qemu versions, which limited
> > +     * the RMA size for complicated and mostly bad reasons.
> > +     */
> > +    if (smc->rma_limit) {
> > +        spapr->rma_size = MIN(spapr->rma_size, smc->rma_limit);
> > +    }
> > +
> > +    if (rma_size < (MIN_RMA_SLOF * MiB)) {
> 
> This looks old copy/paste before the change "spapr: Don't use weird units
> for MIN_RMA_SLOF".
> 
> > +        error_setg(errp,
> > +"pSeries SLOF firmware requires >= %ldMiB guest RMA (Real Mode Area)",
> > +                   MIN_RMA_SLOF);
> 
> Similarly, "MIN_RMA_SLOF / MiB"?

Ah, good catch.  I re-ordered the series at some point and forgot to
fix this up.

> > +        return -1;
> 
> Maybe return 0 in case this function is called with errp !=
> &error_fatal.

Good idea.

-- 
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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