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, 87 insertions, 0 deletions

diff --git a/lib/dhry_run.c b/lib/dhry_run.c
new file mode 100644
index 000000000..4a6d05ce4
--- /dev/null
+++ b/lib/dhry_run.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Dhrystone benchmark test module
+ *
+ * Copyright (C) 2022 Glider bv
+ */
+
+#include "dhry.h"
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/smp.h>
+
+#define DHRY_VAX	1757
+
+static int dhry_run_set(const char *val, const struct kernel_param *kp);
+static const struct kernel_param_ops run_ops = {
+	.flags = KERNEL_PARAM_OPS_FL_NOARG,
+	.set = dhry_run_set,
+};
+static bool dhry_run;
+module_param_cb(run, &run_ops, &dhry_run, 0200);
+MODULE_PARM_DESC(run, "Run the test (default: false)");
+
+static int iterations = -1;
+module_param(iterations, int, 0644);
+MODULE_PARM_DESC(iterations,
+		"Number of iterations through the benchmark (default: auto)");
+
+static void dhry_benchmark(void)
+{
+	unsigned int cpu = get_cpu();
+	int i, n;
+
+	if (iterations > 0) {
+		n = dhry(iterations);
+		goto report;
+	}
+
+	for (i = DHRY_VAX; i > 0; i <<= 1) {
+		n = dhry(i);
+		if (n != -EAGAIN)
+			break;
+	}
+
+report:
+	put_cpu();
+	if (n >= 0)
+		pr_info("CPU%u: Dhrystones per Second: %d (%d DMIPS)\n", cpu,
+			n, n / DHRY_VAX);
+	else if (n == -EAGAIN)
+		pr_err("Please increase the number of iterations\n");
+	else
+		pr_err("Dhrystone benchmark failed error %pe\n", ERR_PTR(n));
+}
+
+static int dhry_run_set(const char *val, const struct kernel_param *kp)
+{
+	int ret;
+
+	if (val) {
+		ret = param_set_bool(val, kp);
+		if (ret)
+			return ret;
+	} else {
+		dhry_run = true;
+	}
+
+	if (dhry_run && system_state == SYSTEM_RUNNING)
+		dhry_benchmark();
+
+	return 0;
+}
+
+static int __init dhry_init(void)
+{
+	if (dhry_run)
+		dhry_benchmark();
+
+	return 0;
+}
+module_init(dhry_init);
+
+MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
+MODULE_DESCRIPTION("Dhrystone benchmark test module");
+MODULE_LICENSE("GPL");