Re: [Qemu-ppc] [RFC PATCH v2 01/21] ppc/xive: introduce a skeleton for the sPAPR XIVE interrupt controller

[David Gibson]

On Mon, Sep 11, 2017 at 07:12:15PM +0200, Cédric Le Goater wrote:
> Start with a couple of attributes for the XIVE sPAPR controller
> model. The number of provisionned IRQ is necessary to size the
> different internal XIVE tables, the number of CPUs is also.
> 
> Signed-off-by: Cédric Le Goater <address@hidden>

[snip]

> +static void spapr_xive_realize(DeviceState *dev, Error **errp)
> +{
> +    sPAPRXive *xive = SPAPR_XIVE(dev);
> +
> +    if (!xive->nr_targets) {
> +        error_setg(errp, "Number of interrupt targets needs to be greater 
> 0");
> +        return;
> +    }
> +    /* We need to be able to allocate at least the IPIs */
> +    if (!xive->nr_irqs || xive->nr_irqs < xive->nr_targets) {
> +        error_setg(errp, "Number of interrupts too small");
> +        return;
> +    }
> +}
> +
> +static Property spapr_xive_properties[] = {
> +    DEFINE_PROP_UINT32("nr-irqs", sPAPRXive, nr_irqs, 0),
> +    DEFINE_PROP_UINT32("nr-targets", sPAPRXive, nr_targets, 0),

I'm a bit uneasy about the number of targets having to be set in
advance: this can make life awkward when CPUs are hotplugged.  I know
there's something similar in xics, but it has caused some hassles, and
we're starting to move away from it.

Do you really need this?

-- 
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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