On Fri, Oct 20, 2017 at 01:56:16PM +0200, Thomas Gleixner wrote: > On Fri, 20 Oct 2017, Christoffer Dall wrote: > > Please Cc lkml when changing genirq core code. > ok, will do so in the future. > > It is currently unclear how to set the VCPU affinity for a percpu_devid > > interrupt , since the Linux irq_data structure describes the state for > > multiple interrupts, 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 > > percpu_devid 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 percpu_devid 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 percpu_devid (PPI) interrupt. > > I have a hard time to understand how adding the comment allows you to set > VCPU affinity .... > Obviously everything already works without adding the comment, however it is not entirely clear how to use the vcpu_into for percpu_devid interrupts, and this patch aims to make that clear, as it is the first user of irq_set_vcpu_affinity for a percpu_devid interrupt which actually uses the vcpu_info pointer. Would you rather that we did not update the documentation or what do you suggest? Thanks, -Christoffer _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
