There is a class of interrupt controllers out there that, once they
have signalled a given interrupt number, will still signal incoming
instances of the *same* interrupt despite the original interrupt
not having been EOIed yet.

As long as the new interrupt reaches the *same* CPU, nothing bad
happens, as that CPU still has its interrupts globally disabled,
and we will only take the new interrupt once the interrupt has
been EOIed.

However, things become more "interesting" if an affinity change comes
in while the interrupt is being handled. More specifically, while
the per-irq lock is being dropped. This results in the affinity change
taking place immediately. At this point, there is nothing that prevents
the interrupt from firing on the new target CPU. We end-up with the
interrupt running concurrently on two CPUs, which isn't a good thing.

And that's where things become worse: the new CPU notices that the
interrupt handling is in progress (irq_may_run() return false), and
*drops the interrupt on the floor*.

The whole race looks like this:

           CPU 0             |          CPU 1
-----------------------------|-----------------------------
interrupt start              |
  handle_fasteoi_irq         | set_affinity(CPU 1)
    handler                  |
    ...                      | interrupt start
    ...                      |   handle_fasteoi_irq -> early out
  handle_fasteoi_irq return  | interrupt end
interrupt end                |

If the interrupt was an edge, too bad. The interrupt is lost, and
the system will eventually die one way or another. Not great.

A way to avoid this situation is to detect this problem at the point
we handle the interrupt on the new target. Instead of dropping the
interrupt, use the resend mechanism to force it to be replayed.

Also, in order to limit the impact of this workaround to the pathetic
architectures that require it, gate it behind a new irq flag aptly
named IRQD_RESEND_WHEN_IN_PROGRESS.

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: James Gowans <jgowans@amazon.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <maz@kernel.org>
Cc: KarimAllah Raslan <karahmed@amazon.com>
Cc: Yipeng Zou <zouyipeng@huawei.com>
Cc: Zhang Jianhua <chris.zjh@huawei.com>
[maz: reworded commit mesage]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230608120021.3273400-3-jgowans@amazon.com

As we're about to use the last bit available in the IRQD_* state
flags, rewrite these flags with BIT(), which ensures that these
constant do not represent a signed value.

Signed-off-by: Marc Zyngier <maz@kernel.org>

All RISC-V platforms have a single HW IPI provided by the INTC local
interrupt controller. The HW method to trigger INTC IPI can be through
external irqchip (e.g. RISC-V AIA), through platform specific device
(e.g. SiFive CLINT timer), or through firmware (e.g. SBI IPI call).

To support multiple IPIs on RISC-V, add a generic IPI multiplexing
mechanism which help us create multiple virtual IPIs using a single
HW IPI. This generic IPI multiplexing is inspired by the Apple AIC
irqchip driver and it is shared by various RISC-V irqchip drivers.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Hector Martin <marcan@marcan.st>
Tested-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230103141221.772261-4-apatel@ventanamicro.com

* irq/loongarch:
  : .
  : Merge the long awaited IRQ support for the LoongArch architecture.
  :
  : From the cover letter:
  :
  : "Currently, LoongArch based processors (e.g. Loongson-3A5000)
  : can only work together with LS7A chipsets. The irq chips in
  : LoongArch computers include CPUINTC (CPU Core Interrupt
  : Controller), LIOINTC (Legacy I/O Interrupt Controller),
  : EIOINTC (Extended I/O Interrupt Controller), PCH-PIC (Main
  : Interrupt Controller in LS7A chipset), PCH-LPC (LPC Interrupt
  : Controller in LS7A chipset) and PCH-MSI (MSI Interrupt Controller)."
  :
  : Note that this comes with non-official, arch private ACPICA
  : definitions until the official ACPICA update is realeased.
  : .
  irqchip / ACPI: Introduce ACPI_IRQ_MODEL_LPIC for LoongArch
  irqchip: Add LoongArch CPU interrupt controller support
  irqchip: Add Loongson Extended I/O interrupt controller support
  irqchip/loongson-liointc: Add ACPI init support
  irqchip/loongson-pch-msi: Add ACPI init support
  irqchip/loongson-pch-pic: Add ACPI init support
  irqchip: Add Loongson PCH LPC controller support
  LoongArch: Prepare to support multiple pch-pic and pch-msi irqdomain
  LoongArch: Use ACPI_GENERIC_GSI for gsi handling
  genirq/generic_chip: Export irq_unmap_generic_chip
  ACPI: irq: Allow acpi_gsi_to_irq() to have an arch-specific fallback
  APCI: irq: Add support for multiple GSI domains
  LoongArch: Provisionally add ACPICA data structures

Signed-off-by: Marc Zyngier <maz@kernel.org>

Some irq controllers have to re-implement a private version for
irq_generic_chip_ops, because they have a different xlate to translate
hwirq. Export irq_unmap_generic_chip to allow reusing in drivers.

Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1658314292-35346-5-git-send-email-lvjianmin@loongson.cn

IRQ affinity masks are not allocated in uniprocessor configurations.
This requires special case non-SMP code in drivers for irqchips which
have per-CPU enable or mask registers.

Since IRQ affinity is always the same in a uniprocessor configuration,
we can provide a correct affinity mask without allocating one per IRQ.

By returning a real cpumask from irq_data_get_affinity_mask even when
SMP is disabled, irqchip drivers which iterate over that mask will
automatically do the right thing.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220701200056.46555-9-samuel@sholland.org

Now that the irq_data_update_affinity helper exists, enforce its use
by returning a a const cpumask from irq_data_get_affinity_mask.

Since the previous commit already updated places that needed to call
irq_data_update_affinity, this commit updates the remaining code that
either did not modify the cpumask or immediately passed the modified
mask to irq_set_affinity.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220701200056.46555-8-samuel@sholland.org

Some architectures and irqchip drivers modify the cpumask returned by
irq_data_get_affinity_mask, usually by copying in to it. This is
problematic for uniprocessor configurations, where the affinity mask
should be constant, as it is known at compile time.

Add and use a setter for the affinity mask, following the pattern of
irq_data_update_effective_affinity. This allows the getter function to
return a const cpumask pointer.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Xen bits
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220701200056.46555-7-samuel@sholland.org

A couple of functions directly reference the affinity mask. Route them
through irq_data_get_affinity_mask so they will pick up any refactoring
done there.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220701200056.46555-6-samuel@sholland.org

In order to move away from gpiolib messing with the internals of
unsuspecting irqchips, add a flag by which irqchips advertise
that they are not to be messed with, and do solemnly swear that
they correctly call into the gpiolib helpers when required.

Also nudge the users into converting their drivers to the
new model.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220419141846.598305-2-maz@kernel.org