From e26dca67fde194340582cfbb0c0bf661825e9e46 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 7 Aug 2025 14:14:41 -0600 Subject: io_uring: add support for IORING_SETUP_CQE_MIXED Normal rings support 16b CQEs for posting completions, while certain features require the ring to be configured with IORING_SETUP_CQE32, as they need to convey more information per completion. This, in turn, makes ALL the CQEs be 32b in size. This is somewhat wasteful and inefficient, particularly when only certain CQEs need to be of the bigger variant. This adds support for setting up a ring with mixed CQE sizes, using IORING_SETUP_CQE_MIXED. When setup in this mode, CQEs posted to the ring may be either 16b or 32b in size. If a CQE is 32b in size, then IORING_CQE_F_32 is set in the CQE flags to indicate that this is the case. If this flag isn't set, the CQE is the normal 16b variant. CQEs on these types of mixed rings may also have IORING_CQE_F_SKIP set. This can happen if the ring is one (small) CQE entry away from wrapping, and an attempt is made to post a 32b CQE. As CQEs must be contigious in the CQ ring, a 32b CQE cannot wrap the ring. For this case, a single dummy CQE is posted with the SKIP flag set. The application should simply ignore those. Signed-off-by: Jens Axboe --- include/uapi/linux/io_uring.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 7af8d10b3aba..5135e1be0390 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -225,6 +225,12 @@ enum io_uring_sqe_flags_bit { /* Use hybrid poll in iopoll process */ #define IORING_SETUP_HYBRID_IOPOLL (1U << 17) +/* + * Allow both 16b and 32b CQEs. If a 32b CQE is posted, it will have + * IORING_CQE_F_32 set in cqe->flags. + */ +#define IORING_SETUP_CQE_MIXED (1U << 18) + enum io_uring_op { IORING_OP_NOP, IORING_OP_READV, -- cgit v1.2.3