[PATCH v3 0/3] genirq: Managed affinity fixes

From: Marc Zyngier
Date: Tue Apr 05 2022 - 19:51:45 EST

John (and later on David) reported[1] a while ago that booting with
maxcpus=1, managed affinity devices would fail to get the interrupts
that were associated with offlined CPUs.

Similarly, Xiongfeng reported[2] that the GICv3 ITS would sometime use
non-housekeeping CPUs instead of the affinity that was passed down as
a parameter.

[1] can be fixed by not trying to activate these interrupts if no CPU
that can satisfy the affinity is present (a patch addressing this was
already posted[3])

[2] is a consequence of affinities containing non-online CPUs being
passed down to the interrupt controller driver and the ITS driver
trying to paper over that by ignoring the affinity parameter and doing
its own (stupid) thing. It would be better to (a) get the core code to
remove the offline CPUs from the affinity mask at all times, and (b)
fix the drivers so that they can trust the core code not to trip them.

This small series, based on 5.18-rc1, addresses the above.



>From v2 [4]:
- Rebased on 5.18-rc1

[1] https://lore.kernel.org/r/78615d08-1764-c895-f3b7-bfddfbcbdfb9@xxxxxxxxxx
[2] https://lore.kernel.org/r/20220124073440.88598-1-wangxiongfeng2@xxxxxxxxxx
[3] https://lore.kernel.org/r/20220307190625.254426-1-maz@xxxxxxxxxx
[4] https://lore.kernel.org/r/20220321193608.975495-1-maz@xxxxxxxxxx

Marc Zyngier (3):
genirq/msi: Shutdown managed interrupts with unsatifiable affinities
genirq: Always limit the affinity to online CPUs
irqchip/gic-v3: Always trust the managed affinity provided by the core

drivers/irqchip/irq-gic-v3-its.c | 2 +-
kernel/irq/manage.c | 25 +++++++++++++++++--------
kernel/irq/msi.c | 15 +++++++++++++++
3 files changed, 33 insertions(+), 9 deletions(-)