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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	John Garry <john.garry@huawei.com>,
	David Decotigny <ddecotig@google.com>,
	Marc Zyngier <maz@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Luiz Capitulino <luizcap@amazon.com>
Subject: [PATCH 5.15 192/206] genirq/msi: Shutdown managed interrupts with unsatifiable affinities
Date: Wed, 30 Nov 2022 19:24:04 +0100
Message-Id: <20221130180537.901616591@linuxfoundation.org>
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From: Luiz Capitulino <luizcap@amazon.com>

From: Marc Zyngier <maz@kernel.org>

commit d802057c7c553ad426520a053da9f9fe08e2c35a upstream.

[ This commit is almost a rewrite because it conflicts with Thomas
  Gleixner's refactoring of this code in v5.17-rc1. I wasn't sure if
  I should drop all the s-o-bs (including Mark's), but decided
  to keep as the original commit ]

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.

The same thing happens when loading a driver using managed interrupts
while CPUs are offline.

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@huawei.com>
Reported-by: David Decotigny <ddecotig@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20220405185040.206297-2-maz@kernel.org

Signed-off-by: Luiz Capitulino <luizcap@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/irq/msi.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -596,6 +596,13 @@ int __msi_domain_alloc_irqs(struct irq_d
 			irqd_clr_can_reserve(irq_data);
 			if (domain->flags & IRQ_DOMAIN_MSI_NOMASK_QUIRK)
 				irqd_set_msi_nomask_quirk(irq_data);
+			if ((info->flags & MSI_FLAG_ACTIVATE_EARLY) &&
+				irqd_affinity_is_managed(irq_data) &&
+				!cpumask_intersects(irq_data_get_affinity_mask(irq_data),
+						    cpu_online_mask)) {
+				irqd_set_managed_shutdown(irq_data);
+				continue;
+			}
 		}
 		ret = irq_domain_activate_irq(irq_data, can_reserve);
 		if (ret)