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, 51 insertions, 0 deletions

diff --git a/arch/x86/lib/cpu.c b/arch/x86/lib/cpu.c
new file mode 100644
index 000000000..d39fba72f
--- /dev/null
+++ b/arch/x86/lib/cpu.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/types.h>
+#include <linux/export.h>
+
+#include <asm/cpu.h>
+#include <asm/cpuid/leaf_types.h>
+
+static unsigned int __x86_family(unsigned int base_fam, unsigned int ext_fam)
+{
+	if (base_fam == 0xf)
+		base_fam += ext_fam;
+
+	return base_fam;
+}
+
+static unsigned int __x86_model(unsigned int family, unsigned int base_model,
+				unsigned int ext_model)
+{
+	if (family >= 0x6)
+		base_model |= ext_model << 4;
+
+	return base_model;
+}
+
+unsigned int x86_family(unsigned int sig)
+{
+	return __x86_family((sig >> 8) & 0xf, (sig >> 20) & 0xff);
+}
+EXPORT_SYMBOL_GPL(x86_family);
+
+unsigned int x86_model(unsigned int sig)
+{
+	return __x86_model(x86_family(sig), (sig >> 4) & 0xf, (sig >> 16) & 0xf);
+}
+EXPORT_SYMBOL_GPL(x86_model);
+
+unsigned int x86_stepping(unsigned int sig)
+{
+	return sig & 0xf;
+}
+EXPORT_SYMBOL_GPL(x86_stepping);
+
+unsigned int cpuid_family(const struct leaf_0x1_0 *l)
+{
+	return __x86_family(l->base_family_id, l->ext_family);
+}
+
+unsigned int cpuid_model(const struct leaf_0x1_0 *l)
+{
+	return __x86_model(cpuid_family(l), l->base_model, l->ext_model);
+}