KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/io_uring/poll.h b/io_uring/poll.h
new file mode 100644
index 000000000..5647c5138
--- /dev/null
+++ b/io_uring/poll.h
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/io_uring_types.h>
+
+#define IO_POLL_ALLOC_CACHE_MAX 32
+
+enum {
+	IO_APOLL_OK,
+	IO_APOLL_ABORTED,
+	IO_APOLL_READY
+};
+
+struct io_poll {
+	struct file			*file;
+	struct wait_queue_head		*head;
+	__poll_t			events;
+	int				retries;
+	struct wait_queue_entry		wait;
+};
+
+struct async_poll {
+	struct io_poll		poll;
+	struct io_poll		*double_poll;
+};
+
+/*
+ * Must only be called inside issue_flags & IO_URING_F_MULTISHOT, or
+ * potentially other cases where we already "own" this poll request.
+ */
+static inline void io_poll_multishot_retry(struct io_kiocb *req)
+{
+	atomic_inc(&req->poll_refs);
+}
+
+int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_poll_add(struct io_kiocb *req, unsigned int issue_flags);
+
+int io_poll_remove_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags);
+
+struct io_cancel_data;
+int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
+		   unsigned issue_flags);
+int io_arm_apoll(struct io_kiocb *req, unsigned issue_flags, __poll_t mask);
+int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags);
+bool io_poll_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx,
+			bool cancel_all);
+
+void io_poll_task_func(struct io_tw_req tw_req, io_tw_token_t tw);