On 12/02/20 11:29, Stefan Hajnoczi wrote: > On Wed, Feb 12, 2020 at 09:31:32AM +0100, Paolo Bonzini wrote: >> On 29/01/20 18:20, Stefan Hajnoczi wrote: >>> + /* Semaphore semantics don't make sense when autoreset is enabled */ >>> + if ((flags & EFD_SEMAPHORE) && (flags & EFD_AUTORESET)) >>> + return -EINVAL; >>> + >> >> I think they do, you just want to subtract 1 instead of setting the >> count to 0. This way, writing 1 would be the post operation on the >> semaphore, while poll() would be the wait operation. > > True! Then EFD_AUTORESET is not a fitting name. EFD_AUTOREAD or > EFD_POLL_READS? Avi's suggestion also makes sense. Switching the event loop from poll() to IORING_OP_POLL_ADD would be good on its own, and then you could make it use IORING_OP_READV for eventfds. In QEMU parlance, perhaps you need a different abstraction than EventNotifier (let's call it WakeupNotifier) which would also use eventfd but it would provide a smaller API. Thanks to the smaller API, it would not need EFD_NONBLOCK, unlike the regular EventNotifier, and it could either set up a poll() handler calling read(), or use IORING_OP_READV when io_uring is in use. Paolo
Attachment:
signature.asc
Description: OpenPGP digital signature
