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, 272 insertions, 0 deletions

diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
new file mode 100644
index 000000000..3ae480476
--- /dev/null
+++ b/io_uring/fdinfo.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/nospec.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "filetable.h"
+#include "sqpoll.h"
+#include "fdinfo.h"
+#include "cancel.h"
+#include "rsrc.h"
+#include "opdef.h"
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+static __cold void common_tracking_show_fdinfo(struct io_ring_ctx *ctx,
+					       struct seq_file *m,
+					       const char *tracking_strategy)
+{
+	seq_puts(m, "NAPI:\tenabled\n");
+	seq_printf(m, "napi tracking:\t%s\n", tracking_strategy);
+	seq_printf(m, "napi_busy_poll_dt:\t%llu\n", ctx->napi_busy_poll_dt);
+	if (ctx->napi_prefer_busy_poll)
+		seq_puts(m, "napi_prefer_busy_poll:\ttrue\n");
+	else
+		seq_puts(m, "napi_prefer_busy_poll:\tfalse\n");
+}
+
+static __cold void napi_show_fdinfo(struct io_ring_ctx *ctx,
+				    struct seq_file *m)
+{
+	unsigned int mode = READ_ONCE(ctx->napi_track_mode);
+
+	switch (mode) {
+	case IO_URING_NAPI_TRACKING_INACTIVE:
+		seq_puts(m, "NAPI:\tdisabled\n");
+		break;
+	case IO_URING_NAPI_TRACKING_DYNAMIC:
+		common_tracking_show_fdinfo(ctx, m, "dynamic");
+		break;
+	case IO_URING_NAPI_TRACKING_STATIC:
+		common_tracking_show_fdinfo(ctx, m, "static");
+		break;
+	default:
+		seq_printf(m, "NAPI:\tunknown mode (%u)\n", mode);
+	}
+}
+#else
+static inline void napi_show_fdinfo(struct io_ring_ctx *ctx,
+				    struct seq_file *m)
+{
+}
+#endif
+
+static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
+{
+	struct io_overflow_cqe *ocqe;
+	struct io_rings *r = ctx->rings;
+	unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1;
+	unsigned int sq_head = READ_ONCE(r->sq.head);
+	unsigned int sq_tail = READ_ONCE(r->sq.tail);
+	unsigned int cq_head = READ_ONCE(r->cq.head);
+	unsigned int cq_tail = READ_ONCE(r->cq.tail);
+	unsigned int sq_shift = 0;
+	unsigned int cq_entries, sq_entries;
+	int sq_pid = -1, sq_cpu = -1;
+	u64 sq_total_time = 0, sq_work_time = 0;
+	unsigned int i;
+
+	if (ctx->flags & IORING_SETUP_SQE128)
+		sq_shift = 1;
+
+	/*
+	 * we may get imprecise sqe and cqe info if uring is actively running
+	 * since we get cached_sq_head and cached_cq_tail without uring_lock
+	 * and sq_tail and cq_head are changed by userspace. But it's ok since
+	 * we usually use these info when it is stuck.
+	 */
+	seq_printf(m, "SqMask:\t0x%x\n", sq_mask);
+	seq_printf(m, "SqHead:\t%u\n", sq_head);
+	seq_printf(m, "SqTail:\t%u\n", sq_tail);
+	seq_printf(m, "CachedSqHead:\t%u\n", data_race(ctx->cached_sq_head));
+	seq_printf(m, "CqMask:\t0x%x\n", cq_mask);
+	seq_printf(m, "CqHead:\t%u\n", cq_head);
+	seq_printf(m, "CqTail:\t%u\n", cq_tail);
+	seq_printf(m, "CachedCqTail:\t%u\n", data_race(ctx->cached_cq_tail));
+	seq_printf(m, "SQEs:\t%u\n", sq_tail - sq_head);
+	sq_entries = min(sq_tail - sq_head, ctx->sq_entries);
+	for (i = 0; i < sq_entries; i++) {
+		unsigned int entry = i + sq_head;
+		struct io_uring_sqe *sqe;
+		unsigned int sq_idx;
+		bool sqe128 = false;
+		u8 opcode;
+
+		if (ctx->flags & IORING_SETUP_NO_SQARRAY)
+			sq_idx = entry & sq_mask;
+		else
+			sq_idx = READ_ONCE(ctx->sq_array[entry & sq_mask]);
+		if (sq_idx > sq_mask)
+			continue;
+
+		sqe = &ctx->sq_sqes[sq_idx << sq_shift];
+		opcode = READ_ONCE(sqe->opcode);
+		if (opcode >= IORING_OP_LAST)
+			continue;
+		opcode = array_index_nospec(opcode, IORING_OP_LAST);
+		if (sq_shift) {
+			sqe128 = true;
+		} else if (io_issue_defs[opcode].is_128) {
+			if (!(ctx->flags & IORING_SETUP_SQE_MIXED)) {
+				seq_printf(m,
+					"%5u: invalid sqe, 128B entry on non-mixed sq\n",
+					sq_idx);
+				break;
+			}
+			if (sq_idx == sq_mask) {
+				seq_printf(m,
+					"%5u: corrupted sqe, wrapping 128B entry\n",
+					sq_idx);
+				break;
+			}
+			sq_head++;
+			i++;
+			sqe128 = true;
+		}
+		seq_printf(m, "%5u: opcode:%s, fd:%d, flags:%x, off:%llu, "
+			      "addr:0x%llx, rw_flags:0x%x, buf_index:%d "
+			      "user_data:%llu",
+			   sq_idx, io_uring_get_opcode(opcode), sqe->fd,
+			   sqe->flags, (unsigned long long) sqe->off,
+			   (unsigned long long) sqe->addr, sqe->rw_flags,
+			   sqe->buf_index, sqe->user_data);
+		if (sqe128) {
+			u64 *sqeb = (void *) (sqe + 1);
+			int size = sizeof(struct io_uring_sqe) / sizeof(u64);
+			int j;
+
+			for (j = 0; j < size; j++) {
+				seq_printf(m, ", e%d:0x%llx", j,
+						(unsigned long long) *sqeb);
+				sqeb++;
+			}
+		}
+		seq_printf(m, "\n");
+		cond_resched();
+	}
+	seq_printf(m, "CQEs:\t%u\n", cq_tail - cq_head);
+	cq_entries = min(cq_tail - cq_head, ctx->cq_entries);
+	for (i = 0; i < cq_entries; i++) {
+		struct io_uring_cqe *cqe;
+		bool cqe32 = false;
+
+		cqe = &r->cqes[(cq_head & cq_mask)];
+		if (cqe->flags & IORING_CQE_F_32 || ctx->flags & IORING_SETUP_CQE32)
+			cqe32 = true;
+		seq_printf(m, "%5u: user_data:%llu, res:%d, flags:%x",
+			   cq_head & cq_mask, cqe->user_data, cqe->res,
+			   cqe->flags);
+		if (cqe32)
+			seq_printf(m, ", extra1:%llu, extra2:%llu",
+					cqe->big_cqe[0], cqe->big_cqe[1]);
+		seq_printf(m, "\n");
+		cq_head++;
+		if (cqe32) {
+			cq_head++;
+			i++;
+		}
+		cond_resched();
+	}
+
+	if (ctx->flags & IORING_SETUP_SQPOLL) {
+		struct io_sq_data *sq = ctx->sq_data;
+		struct task_struct *tsk;
+
+		rcu_read_lock();
+		tsk = rcu_dereference(sq->thread);
+		/*
+		 * sq->thread might be NULL if we raced with the sqpoll
+		 * thread termination.
+		 */
+		if (tsk) {
+			u64 usec;
+
+			get_task_struct(tsk);
+			rcu_read_unlock();
+			usec = io_sq_cpu_usec(tsk);
+			sq_pid = task_pid_nr_ns(tsk,
+						proc_pid_ns(file_inode(m->file)->i_sb));
+			put_task_struct(tsk);
+			sq_cpu = sq->sq_cpu;
+			sq_total_time = usec;
+			sq_work_time = sq->work_time;
+		} else {
+			rcu_read_unlock();
+		}
+	}
+
+	seq_printf(m, "SqThread:\t%d\n", sq_pid);
+	seq_printf(m, "SqThreadCpu:\t%d\n", sq_cpu);
+	seq_printf(m, "SqTotalTime:\t%llu\n", sq_total_time);
+	seq_printf(m, "SqWorkTime:\t%llu\n", sq_work_time);
+	seq_printf(m, "UserFiles:\t%u\n", ctx->file_table.data.nr);
+	for (i = 0; i < ctx->file_table.data.nr; i++) {
+		struct file *f = NULL;
+
+		if (ctx->file_table.data.nodes[i])
+			f = io_slot_file(ctx->file_table.data.nodes[i]);
+		if (f) {
+			seq_printf(m, "%5u: ", i);
+			seq_file_path(m, f, " \t\n\\");
+			seq_puts(m, "\n");
+		}
+	}
+	seq_printf(m, "UserBufs:\t%u\n", ctx->buf_table.nr);
+	for (i = 0; i < ctx->buf_table.nr; i++) {
+		struct io_mapped_ubuf *buf = NULL;
+
+		if (ctx->buf_table.nodes[i])
+			buf = ctx->buf_table.nodes[i]->buf;
+		if (buf)
+			seq_printf(m, "%5u: 0x%llx/%zu\n", i, buf->ubuf, buf->len);
+		else
+			seq_printf(m, "%5u: <none>\n", i);
+	}
+
+	seq_puts(m, "PollList:\n");
+	for (i = 0; i < (1U << ctx->cancel_table.hash_bits); i++) {
+		struct io_hash_bucket *hb = &ctx->cancel_table.hbs[i];
+		struct io_kiocb *req;
+
+		hlist_for_each_entry(req, &hb->list, hash_node)
+			seq_printf(m, "  op=%d, task_works=%d\n", req->opcode,
+					task_work_pending(req->tctx->task));
+	}
+
+	seq_puts(m, "CqOverflowList:\n");
+	spin_lock(&ctx->completion_lock);
+	list_for_each_entry(ocqe, &ctx->cq_overflow_list, list) {
+		struct io_uring_cqe *cqe = &ocqe->cqe;
+
+		seq_printf(m, "  user_data=%llu, res=%d, flags=%x\n",
+			   cqe->user_data, cqe->res, cqe->flags);
+
+	}
+	spin_unlock(&ctx->completion_lock);
+	napi_show_fdinfo(ctx, m);
+}
+
+/*
+ * Caller holds a reference to the file already, we don't need to do
+ * anything else to get an extra reference.
+ */
+__cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
+{
+	struct io_ring_ctx *ctx = file->private_data;
+
+	/*
+	 * Avoid ABBA deadlock between the seq lock and the io_uring mutex,
+	 * since fdinfo case grabs it in the opposite direction of normal use
+	 * cases.
+	 */
+	if (mutex_trylock(&ctx->uring_lock)) {
+		__io_uring_show_fdinfo(ctx, m);
+		mutex_unlock(&ctx->uring_lock);
+	}
+}