Hello! > > Paolo, do you see anything wrong with making > > memory_region_add_eventfd work (slowly) without kvm ioeventfd support? > > > > Sure, it's even been on the todo list for a while. Stefan Hajnoczi had > a patch, the only ugly thing was that it slowed down a little all > non-ioeventfd accesses, but I guess that's okay because it's probably > not measurable. > > http://lists.nongnu.org/archive/html/qemu-devel/2015-07/msg04710.html
Ok, good. So, this has already been tested. Ok, i think i can further extend this patch by: 1. Add a flag to disable memory_region_dispatch_write_ioeventfds(), to be set by KVM code for example. So that with KVM we have even smaller performance degradation. 2. Issue a one-shot warning, like in my current patch, so that the user knows that his/her kernel prevents from getting the best performance. Will it be OK then? Cc'ed also Cornelia because he's taking part in CCW discussion. And the same kind of generic event forwarding could be implemented for CCW then. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia
