[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH v6 1/4] arm: introduce psci_smp_ops

On Mon, 22 Apr 2013, Russell King - ARM Linux wrote:
> > > Now, if the psci stuff can't be relied upon to provide the correct
> > > functionality, then that's a separate problem which needs addressing
> > > differently.
> > > 
> > > This should allow the Xen problem to be resolved, because Xen will
> > > provide the PSCI operations, and it's correct in that case to override
> > > the platform's SMP operations.
> > 
> > Yes, increasing the priority of PSCI helps Xen a lot.
> > In order to completely solve the issue for Xen though, another patch is
> > needed (http://marc.info/?l=linux-kernel&m=136630106201968&w=2) because
> > of the introduction of smp_init.
> Given the way the code in setup.c will work:
> +static bool __init xen_smp_init(void)
> +{
> +#ifdef CONFIG_SMP
> +     /* If we are running on Xen, use PSCI if available.
> +      * In any case do not try to use the native smp_ops. */
> +     if (psci_smp_available())
> +             smp_set_ops(&psci_smp_ops);
> +#endif
> +     return true;
> +}
> Doesn't this just need to return false, and then we'll drop down to
> using PSCI if those operations are available?

If we are running on Xen, we are sure that the only available mechanism
to boot secondary cpus is PSCI; there is no need to try anything else if
that one is not available. This is way xen_smp_init is returning true

However I am going to drop the "xen/arm: introduce xen_early_init, use
PSCI on xen" patch linked above entirely, because I'll just assume that
if we are running on Xen smp_init is going to fail and return false. The
next option on the list is PSCI so in theory we won't have to do
anything special to make it work.

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.