For as long as SMP ARM has existed, IPIs have been handled as something special. The arch code and the interrupt controller exchange a couple of hooks (one to generate an IPI, another to handle it).
Although this is perfectly manageable, it prevents the use of features that we could use if IPIs were Linux IRQs (such as pseudo-NMIs). It also means that each interrupt controller driver has to follow an architecture-specific interface instead of just implementing the base irqchip functionnalities. The arch code also duplicates a number of things that the core irq code already does (such as calling set_irq_regs(), irq_enter()...). This series tries to remedy this on arm/arm64 by offering a new registration interface where the irqchip gives the arch code a range of interrupts to use for IPIs. The arch code requests these as normal interrupts. The bulk of the work is at the interrupt controller level, where all 3 irqchips used on arm64 get converted. Finally, the arm64 code drops the legacy registration interface. The same thing could be done on 32bit as well once the two remaining irqchips using that interface get converted. There is probably more that could be done: statistics are still architecture-private code, for example, and no attempt is made to solve that (apart from hidding the IRQs from /proc/interrupt). This has been tested on a bunch of 32 and 64bit guests. Marc Zyngier (11): genirq: Add fasteoi IPI flow genirq: Allow interrupts to be excluded from /proc/interrupts arm64: Allow IPIs to be handled as normal interrupts ARM: Allow IPIs to be handled as normal interrupts irqchip/gic-v3: Describe the SGI range irqchip/gic-v3: Configure SGIs as standard interrupts irqchip/gic: Refactor SMP configuration irqchip/gic: Configure SGIs as standard interrupts irqchip/gic-common: Don't enable SGIs by default irqchip/bcm2836: Configure mailbox interrupts as standard interrupts arm64: Kill __smp_cross_call and co arch/arm/Kconfig | 1 + arch/arm/include/asm/smp.h | 5 + arch/arm/kernel/smp.c | 97 +++++++++++--- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/irq_work.h | 4 +- arch/arm64/include/asm/smp.h | 6 +- arch/arm64/kernel/smp.c | 98 +++++++++++---- drivers/irqchip/irq-bcm2836.c | 151 ++++++++++++++++++---- drivers/irqchip/irq-gic-common.c | 3 - drivers/irqchip/irq-gic-v3.c | 109 ++++++++++------ drivers/irqchip/irq-gic.c | 203 ++++++++++++++++++------------ include/linux/irq.h | 4 +- kernel/irq/chip.c | 26 ++++ kernel/irq/debugfs.c | 1 + kernel/irq/proc.c | 2 +- kernel/irq/settings.h | 7 ++ 16 files changed, 515 insertions(+), 203 deletions(-) -- 2.26.2