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, 95 insertions, 0 deletions

diff --git a/drivers/sh/intc/userimask.c b/drivers/sh/intc/userimask.c
new file mode 100644
index 000000000..a363f7788
--- /dev/null
+++ b/drivers/sh/intc/userimask.c
@@ -0,0 +1,95 @@
+/*
+ * Support for hardware-assisted userspace interrupt masking.
+ *
+ * Copyright (C) 2010  Paul Mundt
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#define pr_fmt(fmt) "intc: " fmt
+
+#include <linux/errno.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/stat.h>
+#include <linux/sizes.h>
+#include "internals.h"
+
+static void __iomem *uimask;
+
+static ssize_t
+show_intc_userimask(struct device *dev,
+		    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", (__raw_readl(uimask) >> 4) & 0xf);
+}
+
+static ssize_t
+store_intc_userimask(struct device *dev,
+		     struct device_attribute *attr,
+		     const char *buf, size_t count)
+{
+	unsigned long level;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &level);
+	if (ret != 0)
+		return ret;
+
+	/*
+	 * Minimal acceptable IRQ levels are in the 2 - 16 range, but
+	 * these are chomped so as to not interfere with normal IRQs.
+	 *
+	 * Level 1 is a special case on some CPUs in that it's not
+	 * directly settable, but given that USERIMASK cuts off below a
+	 * certain level, we don't care about this limitation here.
+	 * Level 0 on the other hand equates to user masking disabled.
+	 *
+	 * We use the default priority level as a cut off so that only
+	 * special case opt-in IRQs can be mangled.
+	 */
+	if (level >= intc_get_dfl_prio_level())
+		return -EINVAL;
+
+	__raw_writel(0xa5 << 24 | level << 4, uimask);
+
+	return count;
+}
+
+static DEVICE_ATTR(userimask, S_IRUSR | S_IWUSR,
+		   show_intc_userimask, store_intc_userimask);
+
+
+static int __init userimask_sysdev_init(void)
+{
+	struct device *dev_root;
+	int ret = 0;
+
+	if (unlikely(!uimask))
+		return -ENXIO;
+
+	dev_root = bus_get_dev_root(&intc_subsys);
+	if (dev_root) {
+		ret = device_create_file(dev_root, &dev_attr_userimask);
+		put_device(dev_root);
+	}
+	return ret;
+}
+late_initcall(userimask_sysdev_init);
+
+int register_intc_userimask(unsigned long addr)
+{
+	if (unlikely(uimask))
+		return -EBUSY;
+
+	uimask = ioremap(addr, SZ_4K);
+	if (unlikely(!uimask))
+		return -ENOMEM;
+
+	pr_info("userimask support registered for levels 0 -> %d\n",
+		intc_get_dfl_prio_level() - 1);
+
+	return 0;
+}