Re: [RFC PATCHES 00/17] IOMMUFD: Deliver IO page faults to user space

On Fri, Jun 23, 2023 at 02:18:38PM +0800, Baolu Lu wrote:

struct io_uring ring;

io_uring_setup(IOPF_ENTRIES, &ring);

while (1) { struct io_uring_prep_read read; struct io_uring_cqe *cqe;

read.fd = iopf_fd;
read.buf = malloc(IOPF_SIZE);
read.len = IOPF_SIZE;
read.flags = 0;

io_uring_prep_read(&ring, &read);
io_uring_submit(&ring);

// Wait for the read to complete
while ((cqe = io_uring_get_cqe(&ring)) != NULL) {
	// Check if the read completed
	if (cqe->res < 0)
		break;

	if (page_fault_read_completion(cqe)) {
		// Get the fault data
		void *data = cqe->buf;
		size_t size = cqe->res;

		// Handle the page fault
		handle_page_fault(data);

		// Respond the fault
		struct io_uring_prep_write write;
		write.fd = iopf_fd;
		write.buf = malloc(IOPF_RESPONSE_SIZE);
		write.len = IOPF_RESPONSE_SIZE;
		write.flags = 0;

		io_uring_prep_write(&ring, &write);
        			io_uring_submit(&ring);
	}

	// Reap the cqe
	io_uring_cqe_free(&ring, cqe);
}

}

Did I understand you correctly?

Yes, basically this is the right idea. There are more complex ways to use the iouring that would be faster still.

And the kernel side can have support to speed it up as well.

I'm wondering if we should be pushing invalidations on io_uring as well?

Jason