On Sun, 05 May 2019 12:15:51 +0100, Heyi Guo <guoheyi@xxxxxxxxxx> wrote: > > BTW since its_irq_set_vcpu_affinity() is already in atomic context, > do we really need a separate lock its_dev->event_map.vlpi_lock? I > didn't find anywhere outside its_irq_set_vcpu_affinity() call chain > acquires this lock. The reason is that the vlpi_maps array covers the whole of the generating device, and not just a single interrupt. Relying on the irq_desc lock to protect the array wouldn't work, as you could still have concurrent accesses to the array (map, unmap and get all access the same data). So one way or another, we need some form of mutual exclusion at this level. I guess one of the design mistakes that we have in the current code is that there is no "device wide" operation, and that we rely on map/unmap to perform the allocations on demand in the low level code. What we could potentially do would be to move this allocation higher up in the stack, and track the first time an LPI is turned into a VLPI at that level. That's an invasive change though... Thanks, M. -- Jazz is not dead, it just smell funny. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
