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, 183 insertions, 0 deletions

diff --git a/drivers/interconnect/debugfs-client.c b/drivers/interconnect/debugfs-client.c
new file mode 100644
index 000000000..91f86d923
--- /dev/null
+++ b/drivers/interconnect/debugfs-client.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#include <linux/debugfs.h>
+#include <linux/interconnect.h>
+#include <linux/platform_device.h>
+
+#include "internal.h"
+
+/*
+ * This can be dangerous, therefore don't provide any real compile time
+ * configuration option for this feature.
+ * People who want to use this will need to modify the source code directly.
+ */
+#undef INTERCONNECT_ALLOW_WRITE_DEBUGFS
+
+#if defined(INTERCONNECT_ALLOW_WRITE_DEBUGFS) && defined(CONFIG_DEBUG_FS)
+
+static LIST_HEAD(debugfs_paths);
+static DEFINE_MUTEX(debugfs_lock);
+
+static struct platform_device *pdev;
+static struct icc_path *cur_path;
+
+static char *src_node;
+static char *dst_node;
+static u32 avg_bw;
+static u32 peak_bw;
+static u32 tag;
+
+struct debugfs_path {
+	const char *src;
+	const char *dst;
+	struct icc_path *path;
+	struct list_head list;
+};
+
+static struct icc_path *get_path(const char *src, const char *dst)
+{
+	struct debugfs_path *path;
+
+	list_for_each_entry(path, &debugfs_paths, list) {
+		if (!strcmp(path->src, src) && !strcmp(path->dst, dst))
+			return path->path;
+	}
+
+	return NULL;
+}
+
+static int icc_get_set(void *data, u64 val)
+{
+	struct debugfs_path *debugfs_path;
+	char *src, *dst;
+	int ret = 0;
+
+	mutex_lock(&debugfs_lock);
+
+	rcu_read_lock();
+	src = rcu_dereference(src_node);
+	dst = rcu_dereference(dst_node);
+
+	/*
+	 * If we've already looked up a path, then use the existing one instead
+	 * of calling icc_get() again. This allows for updating previous BW
+	 * votes when "get" is written to multiple times for multiple paths.
+	 */
+	cur_path = get_path(src, dst);
+	if (cur_path) {
+		rcu_read_unlock();
+		goto out;
+	}
+
+	src = kstrdup(src, GFP_ATOMIC);
+	dst = kstrdup(dst, GFP_ATOMIC);
+	rcu_read_unlock();
+
+	if (!src || !dst) {
+		ret = -ENOMEM;
+		goto err_free;
+	}
+
+	cur_path = icc_get(&pdev->dev, src, dst);
+	if (IS_ERR(cur_path)) {
+		ret = PTR_ERR(cur_path);
+		goto err_free;
+	}
+
+	debugfs_path = kzalloc_obj(*debugfs_path);
+	if (!debugfs_path) {
+		ret = -ENOMEM;
+		goto err_put;
+	}
+
+	debugfs_path->path = cur_path;
+	debugfs_path->src = src;
+	debugfs_path->dst = dst;
+	list_add_tail(&debugfs_path->list, &debugfs_paths);
+
+	goto out;
+
+err_put:
+	icc_put(cur_path);
+err_free:
+	kfree(src);
+	kfree(dst);
+out:
+	mutex_unlock(&debugfs_lock);
+	return ret;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(icc_get_fops, NULL, icc_get_set, "%llu\n");
+
+static int icc_commit_set(void *data, u64 val)
+{
+	int ret;
+
+	mutex_lock(&debugfs_lock);
+
+	if (!cur_path) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (IS_ERR(cur_path)) {
+		ret = PTR_ERR(cur_path);
+		goto out;
+	}
+
+	icc_set_tag(cur_path, tag);
+	ret = icc_set_bw(cur_path, avg_bw, peak_bw);
+out:
+	mutex_unlock(&debugfs_lock);
+	return ret;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(icc_commit_fops, NULL, icc_commit_set, "%llu\n");
+
+int icc_debugfs_client_init(struct dentry *icc_dir)
+{
+	struct dentry *client_dir;
+	int ret;
+
+	pdev = platform_device_alloc("icc-debugfs-client", PLATFORM_DEVID_NONE);
+	if (!pdev)
+		return -ENOMEM;
+
+	ret = platform_device_add(pdev);
+	if (ret) {
+		pr_err("%s: failed to add platform device: %d\n", __func__, ret);
+		platform_device_put(pdev);
+		return ret;
+	}
+
+	src_node = kstrdup("", GFP_KERNEL);
+	dst_node = kstrdup("", GFP_KERNEL);
+	if (!src_node || !dst_node) {
+		kfree(dst_node);
+		kfree(src_node);
+		return -ENOMEM;
+	}
+
+	client_dir = debugfs_create_dir("test_client", icc_dir);
+
+	debugfs_create_str("src_node", 0600, client_dir, &src_node);
+	debugfs_create_str("dst_node", 0600, client_dir, &dst_node);
+	debugfs_create_file("get", 0200, client_dir, NULL, &icc_get_fops);
+	debugfs_create_u32("avg_bw", 0600, client_dir, &avg_bw);
+	debugfs_create_u32("peak_bw", 0600, client_dir, &peak_bw);
+	debugfs_create_u32("tag", 0600, client_dir, &tag);
+	debugfs_create_file("commit", 0200, client_dir, NULL, &icc_commit_fops);
+
+	return 0;
+}
+
+#else
+
+int icc_debugfs_client_init(struct dentry *icc_dir)
+{
+	return 0;
+}
+
+#endif