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, 103 insertions, 0 deletions

diff --git a/include/xen/xen.h b/include/xen/xen.h
new file mode 100644
index 000000000..f280c5dcf
--- /dev/null
+++ b/include/xen/xen.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _XEN_XEN_H
+#define _XEN_XEN_H
+
+#include <linux/types.h>
+
+enum xen_domain_type {
+	XEN_NATIVE,		/* running on bare hardware    */
+	XEN_PV_DOMAIN,		/* running in a PV domain      */
+	XEN_HVM_DOMAIN,		/* running in a Xen hvm domain */
+};
+
+#ifdef CONFIG_XEN
+extern enum xen_domain_type xen_domain_type;
+#else
+#define xen_domain_type		XEN_NATIVE
+#endif
+
+#ifdef CONFIG_XEN_PVH
+extern bool xen_pvh;
+#else
+#define xen_pvh			0
+#endif
+
+#ifdef CONFIG_X86
+#include <asm/cpufeature.h>
+
+#define xen_pv_domain()		(cpu_feature_enabled(X86_FEATURE_XENPV))
+#else
+#define xen_pv_domain()		0
+#endif
+
+#define xen_domain()		(xen_domain_type != XEN_NATIVE)
+#define xen_hvm_domain()	(xen_domain_type == XEN_HVM_DOMAIN)
+#define xen_pvh_domain()	(xen_pvh)
+
+extern uint32_t xen_start_flags;
+
+#ifdef CONFIG_XEN_PV
+extern bool xen_pv_pci_possible;
+#else
+#define xen_pv_pci_possible	0
+#endif
+
+#include <xen/interface/hvm/start_info.h>
+extern struct hvm_start_info pvh_start_info;
+void xen_prepare_pvh(void);
+struct pt_regs;
+void xen_pv_evtchn_do_upcall(struct pt_regs *regs);
+
+#ifdef CONFIG_XEN_DOM0
+#include <xen/interface/xen.h>
+#include <asm/xen/hypervisor.h>
+
+#define xen_initial_domain()	(xen_domain() && \
+				 (xen_start_flags & SIF_INITDOMAIN))
+#else  /* !CONFIG_XEN_DOM0 */
+#define xen_initial_domain()	(0)
+#endif	/* CONFIG_XEN_DOM0 */
+
+struct bio_vec;
+struct page;
+
+bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
+		const struct page *page);
+
+#if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
+extern u64 xen_saved_max_mem_size;
+#endif
+
+#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
+extern unsigned long xen_unpopulated_pages;
+int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages);
+void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages);
+#include <linux/ioport.h>
+int arch_xen_unpopulated_init(struct resource **res);
+#else
+#define xen_unpopulated_pages 0UL
+#include <xen/balloon.h>
+static inline int xen_alloc_unpopulated_pages(unsigned int nr_pages,
+		struct page **pages)
+{
+	return xen_alloc_ballooned_pages(nr_pages, pages);
+}
+static inline void xen_free_unpopulated_pages(unsigned int nr_pages,
+		struct page **pages)
+{
+	xen_free_ballooned_pages(nr_pages, pages);
+}
+#endif
+
+#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI) && defined(CONFIG_X86)
+bool __init xen_processor_present(uint32_t acpi_id);
+#else
+#include <linux/bug.h>
+static inline bool xen_processor_present(uint32_t acpi_id)
+{
+	BUG();
+	return false;
+}
+#endif
+
+#endif	/* _XEN_XEN_H */