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, 53 insertions, 0 deletions

diff --git a/drivers/acpi/acpi_ffh.c b/drivers/acpi/acpi_ffh.c
new file mode 100644
index 000000000..8d5126963
--- /dev/null
+++ b/drivers/acpi/acpi_ffh.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Author: Sudeep Holla <sudeep.holla@arm.com>
+ * Copyright 2022 Arm Limited
+ */
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/completion.h>
+#include <linux/idr.h>
+#include <linux/io.h>
+
+static struct acpi_ffh_info ffh_ctx;
+
+int __weak acpi_ffh_address_space_arch_setup(void *handler_ctxt,
+					     void **region_ctxt)
+{
+	return -EOPNOTSUPP;
+}
+
+int __weak acpi_ffh_address_space_arch_handler(acpi_integer *value,
+					       void *region_context)
+{
+	return -EOPNOTSUPP;
+}
+
+static acpi_status
+acpi_ffh_address_space_setup(acpi_handle region_handle, u32 function,
+			     void *handler_context,  void **region_context)
+{
+	return acpi_ffh_address_space_arch_setup(handler_context,
+						 region_context);
+}
+
+static acpi_status
+acpi_ffh_address_space_handler(u32 function, acpi_physical_address addr,
+			       u32 bits, acpi_integer *value,
+			       void *handler_context, void *region_context)
+{
+	return acpi_ffh_address_space_arch_handler(value, region_context);
+}
+
+void __init acpi_init_ffh(void)
+{
+	acpi_status status;
+
+	status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
+						    ACPI_ADR_SPACE_FIXED_HARDWARE,
+						    &acpi_ffh_address_space_handler,
+						    &acpi_ffh_address_space_setup,
+						    &ffh_ctx);
+	if (ACPI_FAILURE(status))
+		pr_alert("OperationRegion handler could not be installed\n");
+}