Re: [PATCH] powerpc/xics: Adjust interrupt receive priority for offline cpus

[Michael Neuling <mikey@neuling.org>]

On Thu, 2017-02-23 at 16:24 +0530, Vaidyanathan Srinivasan wrote:
> Offline CPUs need to receive IPIs through XIVE when they are
> in stop state and wakeup from that state.
>=20
> Reduce interrupt receive priority in order to receive XIVE
> wakeup interrupts when in offline state.
>=20
> LOWEST_PRIORITY would allow all interrupts to be delivered
> as wakeup events.

This needs to be expanded to explain why "DEFAULT" doesn't work in this cas=
e.

This also needs an explicit statement that "It fixes onlining of CPUs on
POWER9".  I'd even advocate for making that the patch subject.=20

Also if it's the right fix, it needs a cc:stable.

Mikey


> Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
> ---
> =C2=A0arch/powerpc/sysdev/xics/xics-common.c | 2 +-
> =C2=A01 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/arch/powerpc/sysdev/xics/xics-common.c
> b/arch/powerpc/sysdev/xics/xics-common.c
> index 69d858e..c674a9d 100644
> --- a/arch/powerpc/sysdev/xics/xics-common.c
> +++ b/arch/powerpc/sysdev/xics/xics-common.c
> @@ -199,7 +199,7 @@ void xics_migrate_irqs_away(void)
> =C2=A0	xics_set_cpu_giq(xics_default_distrib_server, 0);
> =C2=A0
> =C2=A0	/* Allow IPIs again... */
> -	icp_ops->set_priority(DEFAULT_PRIORITY);
> +	icp_ops->set_priority(LOWEST_PRIORITY);
> =C2=A0
> =C2=A0	for_each_irq_desc(virq, desc) {
> =C2=A0		struct irq_chip *chip;