io_uring: user registered clockid for wait timeouts

Add a new registration opcode IORING_REGISTER_CLOCK, which allows the
user to select which clock id it wants to use with CQ waiting timeouts.
It only allows a subset of all posix clocks and currently supports
CLOCK_MONOTONIC and CLOCK_BOOTTIME.

Suggested-by: Lewis Baker <lewissbaker@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/98f2bc8a3c36cdf8f0e6a275245e81e903459703.1723039801.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 46 insertions, 3 deletions

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 5282f9887440..20229e72b65c 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2377,7 +2377,8 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	ret = 0;
 	if (iowq->timeout == KTIME_MAX)
 		schedule();
-	else if (!schedule_hrtimeout(&iowq->timeout, HRTIMER_MODE_ABS))
+	else if (!schedule_hrtimeout_range_clock(&iowq->timeout, 0,
+						 HRTIMER_MODE_ABS, ctx->clockid))
 		ret = -ETIME;
 	current->in_iowait = 0;
 	return ret;
@@ -2422,7 +2423,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags,
 
 		iowq.timeout = timespec64_to_ktime(ts);
 		if (!(flags & IORING_ENTER_ABS_TIMER))
-			iowq.timeout = ktime_add(iowq.timeout, ktime_get());
+			iowq.timeout = ktime_add(iowq.timeout, io_get_time(ctx));
 	}
 
 	if (sig) {
@@ -3424,6 +3425,9 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
 	if (!ctx)
 		return -ENOMEM;
 
+	ctx->clockid = CLOCK_MONOTONIC;
+	ctx->clock_offset = 0;
+
 	if ((ctx->flags & IORING_SETUP_DEFER_TASKRUN) &&
 	    !(ctx->flags & IORING_SETUP_IOPOLL) &&
 	    !(ctx->flags & IORING_SETUP_SQPOLL))
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index c2acf6180845..9935819f12b7 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -437,6 +437,14 @@ static inline bool io_file_can_poll(struct io_kiocb *req)
 	return false;
 }
 
+static inline ktime_t io_get_time(struct io_ring_ctx *ctx)
+{
+	if (ctx->clockid == CLOCK_MONOTONIC)
+		return ktime_get();
+
+	return ktime_get_with_offset(ctx->clock_offset);
+}
+
 enum {
 	IO_CHECK_CQ_OVERFLOW_BIT,
 	IO_CHECK_CQ_DROPPED_BIT,
diff --git a/io_uring/napi.c b/io_uring/napi.c
index d78fcbecdd27..d0cf694d0172 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -283,7 +283,7 @@ void __io_napi_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq)
 
 	iowq->napi_busy_poll_dt = READ_ONCE(ctx->napi_busy_poll_dt);
 	if (iowq->timeout != KTIME_MAX) {
-		ktime_t dt = ktime_sub(iowq->timeout, ktime_get());
+		ktime_t dt = ktime_sub(iowq->timeout, io_get_time(ctx));
 
 		iowq->napi_busy_poll_dt = min_t(u64, iowq->napi_busy_poll_dt, dt);
 	}
diff --git a/io_uring/register.c b/io_uring/register.c
index e3c20be5a198..57cb85c42526 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -335,6 +335,31 @@ err:
 	return ret;
 }
 
+static int io_register_clock(struct io_ring_ctx *ctx,
+			     struct io_uring_clock_register __user *arg)
+{
+	struct io_uring_clock_register reg;
+
+	if (copy_from_user(&reg, arg, sizeof(reg)))
+		return -EFAULT;
+	if (memchr_inv(&reg.__resv, 0, sizeof(reg.__resv)))
+		return -EINVAL;
+
+	switch (reg.clockid) {
+	case CLOCK_MONOTONIC:
+		ctx->clock_offset = 0;
+		break;
+	case CLOCK_BOOTTIME:
+		ctx->clock_offset = TK_OFFS_BOOT;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	ctx->clockid = reg.clockid;
+	return 0;
+}
+
 static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			       void __user *arg, unsigned nr_args)
 	__releases(ctx->uring_lock)
@@ -511,6 +536,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			break;
 		ret = io_unregister_napi(ctx, arg);
 		break;
+	case IORING_REGISTER_CLOCK:
+		ret = -EINVAL;
+		if (!arg || nr_args)
+			break;
+		ret = io_register_clock(ctx, arg);
+		break;
 	default:
 		ret = -EINVAL;
 		break;