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Date: Mon, 14 Mar 2022 16:27:10 +0100 From: Thomas Gleixner <tglx@...utronix.de> To: Marc Zyngier <maz@...nel.org>, linux-kernel@...r.kernel.org Cc: John Garry <john.garry@...wei.com>, David Decotigny <ddecotig@...gle.com> Subject: Re: [PATCH] genirq/msi: Shutdown managed interrupts with unsatifiable affinities On Mon, Mar 07 2022 at 19:06, Marc Zyngier wrote: > When booting with maxcpus=<small number>, interrupt controllers > such as the GICv3 ITS may not be able to satisfy the affinity of > some managed interrupts, as some of the HW resources are simply > not available. This is also true if you have offlined lots of CPUs, right? > In order to deal with this, do not try to activate such interrupt > if there is no online CPU capable of handling it. Instead, place > it in shutdown state. Once a capable CPU shows up, it will be > activated. > > Reported-by: John Garry <john.garry@...wei.com> > Reported-by: David Decotigny <ddecotig@...gle.com> > Signed-off-by: Marc Zyngier <maz@...nel.org> > --- > kernel/irq/msi.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c > index 2bdfce5edafd..aa84ce84c2ec 100644 > --- a/kernel/irq/msi.c > +++ b/kernel/irq/msi.c > @@ -818,6 +818,18 @@ static int msi_init_virq(struct irq_domain *domain, int virq, unsigned int vflag > irqd_clr_can_reserve(irqd); > if (vflags & VIRQ_NOMASK_QUIRK) > irqd_set_msi_nomask_quirk(irqd); > + > + /* > + * If the interrupt is managed but no CPU is available > + * to service it, shut it down until better times. > + */ > + if ((vflags & VIRQ_ACTIVATE) && > + irqd_affinity_is_managed(irqd) && > + !cpumask_intersects(irq_data_get_affinity_mask(irqd), > + cpu_online_mask)) { > + irqd_set_managed_shutdown(irqd); Hrm. Why is this in the !CAN_RESERVE path and not before the actual activation call? Thanks, tglx
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