On Wed, Nov 15, 2023 at 01:17:06PM +0800, Liu, Jing2 wrote: > This is the right way to approach it, > > I learned that there was discussion about using io_uring to get the > page fault without > > eventfd notification in [1], and I am new at io_uring and studying the > man page of > > liburing, but there're questions in my mind on how can QEMU get the > coming page fault > > with a good performance. > > Since both QEMU and Kernel don't know when comes faults, after QEMU > submits one > > read task to io_uring, we want kernel pending until fault comes. While > based on > > hwpt_fault_fops_read() in [patch v2 4/6], it just returns 0 since > there's now no fault, > > thus this round of read completes to CQ but it's not what we want. So > I'm wondering > > how kernel pending on the read until fault comes. Does fops callback > need special work to Implement a fops with poll support that triggers when a new event is pushed and everything will be fine. There are many examples in the kernel. The ones in the mlx5 vfio driver spring to mind as a scheme I recently looked at. Jason
