It is currently unclear how to set the VCPU affinity for an interrupt which is of the per-CPU kind, since the Linux irq_data structure describes the state for multiple interrupts when the interrupt is a per-CPU interrupt, one for each physical CPU on the system. Since each such interrupt can be associated with different VCPUs or none at all, associating a single VCPU state with such an interrupt does not capture the necessary semantics. The implementers of irq_set_affinity are the Intel and AMD IOMMUs, and the ARM GIC irqchip. The Intel and AMD callers do not appear to use per-CPU interrupts, and the ARM GIC implementation only checks the pointer against NULL vs. non-NULL. Therefore, simply update the function documentation to explain the expected use in the context of per-CPU interrupts, allowing future changes or additions to irqchip implementers to do the right thing. This allows us to set the VCPU affinity for the virtual timer interrupt in KVM/ARM, which is a per-CPU (PPI) interrupt. Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Christoffer Dall <cdall@xxxxxxxxxx> --- kernel/irq/manage.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 5624b2d..050b9f6 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -381,7 +381,8 @@ int irq_select_affinity_usr(unsigned int irq) /** * irq_set_vcpu_affinity - Set vcpu affinity for the interrupt * @irq: interrupt number to set affinity - * @vcpu_info: vCPU specific data + * @vcpu_info: vCPU specific data or pointer to a percpu array of vCPU + * specific data for per-CPU interrupts * * This function uses the vCPU specific data to set the vCPU * affinity for an irq. The vCPU specific data is passed from -- 2.9.0
