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Date: Mon, 7 Mar 2022 17:36:18 -0800 From: David Decotigny <decot@...gle.com> To: Marc Zyngier <maz@...nel.org> Cc: David Decotigny <decot+git@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v1 1/1] irqchip/gic-v3-its: fixup IRQ affinities to account for online CPUs -- David Decotigny -- Platforms, US SVL MAT3 On Sat, Mar 5, 2022 at 3:24 AM Marc Zyngier <maz@...nel.org> wrote: > > On Fri, 04 Mar 2022 19:52:38 +0000, > David Decotigny <decot+git@...gle.com> wrote: > > > > From: David Decotigny <ddecotig@...gle.com> > > > > In some cases (eg. when booting with maxcpus=X), it is possible that > > the preset IRQ affinity masks don't intersect with the set of online > > CPUs. This patch extends the fallback strategy implemented when > > IRQD_AFFINITY_MANAGED is not set to all cases. This is logged the > > first time that happens. > > > > Fixes: c5d6082d35e0 ("irqchip/gic-v3-its: Balance initial LPI affinity across CPUs") > > > > Missing SoB? > > > --- > > drivers/irqchip/irq-gic-v3-its.c | 13 ++++++------- > > 1 file changed, 6 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > > index cd772973114a..de862fd9ad73 100644 > > --- a/drivers/irqchip/irq-gic-v3-its.c > > +++ b/drivers/irqchip/irq-gic-v3-its.c > > @@ -1618,11 +1618,6 @@ static int its_select_cpu(struct irq_data *d, > > /* Try the intersection of the affinity and online masks */ > > cpumask_and(tmpmask, aff_mask, cpu_online_mask); > > > > - /* If that doesn't fly, the online mask is the last resort */ > > - if (cpumask_empty(tmpmask)) > > - cpumask_copy(tmpmask, cpu_online_mask); > > - > > - cpu = cpumask_pick_least_loaded(d, tmpmask); > > } else { > > cpumask_and(tmpmask, irq_data_get_affinity_mask(d), cpu_online_mask); > > > > @@ -1630,9 +1625,13 @@ static int its_select_cpu(struct irq_data *d, > > if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) && > > node != NUMA_NO_NODE) > > cpumask_and(tmpmask, tmpmask, cpumask_of_node(node)); > > - > > - cpu = cpumask_pick_least_loaded(d, tmpmask); > > } > > + > > + /* If that doesn't fly, the online mask is the last resort */ > > + if (WARN_ON_ONCE(cpumask_empty(tmpmask))) > > + cpumask_copy(tmpmask, cpu_online_mask); > > + > > + cpu = cpumask_pick_least_loaded(d, tmpmask); > > out: > > free_cpumask_var(tmpmask); > > > > Known issue, see [1] and [2]. > > I don't think the above is the right approach. For managed interrupts, > we shouldn't try and enable these interrupts until the CPUs are up, > and activating them on *another* CPU breaks the abstraction entirely. > > The right way to do it would be to not activate them (marking them as > shutdown) until the CPUs are up and running, similarly to what x86 > does (but we obviously can't reuse the matrix allocator for that). > Looking into this is on my TODO list, just didn't get the time to work > on it. Indeed: thanks for https://lore.kernel.org/lkml/20220307190625.254426-1-maz@kernel.org/ , worked for us ! ... And then please ignore my patch. > > M. > > [1] https://lore.kernel.org/r/78615d08-1764-c895-f3b7-bfddfbcbdfb9@huawei.com > [2] https://lore.kernel.org/r/20220124073440.88598-1-wangxiongfeng2@huawei.com > > -- > Without deviation from the norm, progress is not possible.
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