On 2015/8/27 5:40, Thomas Gleixner wrote: > But back to the IPIs. We need infrastructure and DT support to: > > 1) reserve an IPI > > 2) send an IPI > > 3) request/free an IPI > > #1 We have no infrastructure for that, but we definitely need one. > > We can look at the IPI as a single linux irq number which is > replicated on all cpu cores. The replication can happen in hardware > or by software, but that depends on the underlying root irq > controller. How that is implemented does not matter for the > reservation. > > The most flexible and platform independent solution would be to > describe the IPI space as a seperate irq domain. In most cases this > would be a hierarchical domain stacked on the root irq domain: > > [IPI-domain] --> [GIC-MIPS-domain] > > on x86 this would be: > > [IPI-domain] --> [vector-domain] > > That needs some change how the IPIs which are used by the kernel > (rescheduling, function call ..) are set up, but we get a proper > management and collision avoidance that way. Depending on the > platform we could actually remove the whole IPI compile time > reservation and hand out IPIs at boot time on demand and > dynamically. Hi Thomas, Good point:) That will make the code more clear. Thanks! Gerry
