x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 155 insertions, 0 deletions

diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
new file mode 100644
index 000000000..d738d3199
--- /dev/null
+++ b/drivers/cpufreq/cpufreq_userspace.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ *  linux/drivers/cpufreq/cpufreq_userspace.c
+ *
+ *  Copyright (C)  2001 Russell King
+ *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cpufreq.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+
+struct userspace_policy {
+	unsigned int is_managed;
+	unsigned int setspeed;
+	struct mutex mutex;
+};
+
+/**
+ * cpufreq_set - set the CPU frequency
+ * @policy: pointer to policy struct where freq is being set
+ * @freq: target frequency in kHz
+ *
+ * Sets the CPU frequency to freq.
+ */
+static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
+{
+	int ret = -EINVAL;
+	struct userspace_policy *userspace = policy->governor_data;
+
+	pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
+
+	mutex_lock(&userspace->mutex);
+	if (!userspace->is_managed)
+		goto err;
+
+	userspace->setspeed = freq;
+
+	ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
+ err:
+	mutex_unlock(&userspace->mutex);
+	return ret;
+}
+
+static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
+{
+	struct userspace_policy *userspace = policy->governor_data;
+
+	return sprintf(buf, "%u\n", userspace->setspeed);
+}
+
+static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
+{
+	struct userspace_policy *userspace;
+
+	userspace = kzalloc_obj(*userspace);
+	if (!userspace)
+		return -ENOMEM;
+
+	mutex_init(&userspace->mutex);
+
+	policy->governor_data = userspace;
+	return 0;
+}
+
+/*
+ * Any routine that writes to the policy struct will hold the "rwsem" of
+ * policy struct that means it is free to free "governor_data" here.
+ */
+static void cpufreq_userspace_policy_exit(struct cpufreq_policy *policy)
+{
+	kfree(policy->governor_data);
+	policy->governor_data = NULL;
+}
+
+static int cpufreq_userspace_policy_start(struct cpufreq_policy *policy)
+{
+	struct userspace_policy *userspace = policy->governor_data;
+
+	BUG_ON(!policy->cur);
+	pr_debug("started managing cpu %u\n", policy->cpu);
+
+	mutex_lock(&userspace->mutex);
+	userspace->is_managed = 1;
+	userspace->setspeed = policy->cur;
+	mutex_unlock(&userspace->mutex);
+	return 0;
+}
+
+static void cpufreq_userspace_policy_stop(struct cpufreq_policy *policy)
+{
+	struct userspace_policy *userspace = policy->governor_data;
+
+	pr_debug("managing cpu %u stopped\n", policy->cpu);
+
+	mutex_lock(&userspace->mutex);
+	userspace->is_managed = 0;
+	userspace->setspeed = 0;
+	mutex_unlock(&userspace->mutex);
+}
+
+static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
+{
+	struct userspace_policy *userspace = policy->governor_data;
+
+	mutex_lock(&userspace->mutex);
+
+	pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz, last set to %u kHz\n",
+		 policy->cpu, policy->min, policy->max, policy->cur, userspace->setspeed);
+
+	if (policy->max < userspace->setspeed)
+		__cpufreq_driver_target(policy, policy->max,
+					CPUFREQ_RELATION_H);
+	else if (policy->min > userspace->setspeed)
+		__cpufreq_driver_target(policy, policy->min,
+					CPUFREQ_RELATION_L);
+	else
+		__cpufreq_driver_target(policy, userspace->setspeed,
+					CPUFREQ_RELATION_L);
+
+	mutex_unlock(&userspace->mutex);
+}
+
+static struct cpufreq_governor cpufreq_gov_userspace = {
+	.name		= "userspace",
+	.init		= cpufreq_userspace_policy_init,
+	.exit		= cpufreq_userspace_policy_exit,
+	.start		= cpufreq_userspace_policy_start,
+	.stop		= cpufreq_userspace_policy_stop,
+	.limits		= cpufreq_userspace_policy_limits,
+	.store_setspeed	= cpufreq_set,
+	.show_setspeed	= show_speed,
+	.owner		= THIS_MODULE,
+	.flags		= CPUFREQ_GOV_STRICT_TARGET,
+};
+
+MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
+		"Russell King <rmk@arm.linux.org.uk>");
+MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
+MODULE_LICENSE("GPL");
+
+#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
+struct cpufreq_governor *cpufreq_default_governor(void)
+{
+	return &cpufreq_gov_userspace;
+}
+#endif
+
+cpufreq_governor_init(cpufreq_gov_userspace);
+cpufreq_governor_exit(cpufreq_gov_userspace);