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, 133 insertions, 0 deletions

diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
new file mode 100644
index 000000000..b815d2a75
--- /dev/null
+++ b/drivers/firmware/efi/fdtparams.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) "efi: " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/efi.h>
+#include <linux/libfdt.h>
+#include <linux/of_fdt.h>
+
+#include <linux/unaligned.h>
+
+enum {
+	SYSTAB,
+	MMBASE,
+	MMSIZE,
+	DCSIZE,
+	DCVERS,
+
+	PARAMCOUNT
+};
+
+static __initconst const char name[][22] = {
+	[SYSTAB] = "System Table         ",
+	[MMBASE] = "MemMap Address       ",
+	[MMSIZE] = "MemMap Size          ",
+	[DCSIZE] = "MemMap Desc. Size    ",
+	[DCVERS] = "MemMap Desc. Version ",
+};
+
+static __initconst const struct {
+	const char	path[17];
+	u8		paravirt;
+	const char	params[PARAMCOUNT][26];
+} dt_params[] = {
+	{
+#ifdef CONFIG_XEN    //  <-------17------>
+		.path = "/hypervisor/uefi",
+		.paravirt = 1,
+		.params = {
+			[SYSTAB] = "xen,uefi-system-table",
+			[MMBASE] = "xen,uefi-mmap-start",
+			[MMSIZE] = "xen,uefi-mmap-size",
+			[DCSIZE] = "xen,uefi-mmap-desc-size",
+			[DCVERS] = "xen,uefi-mmap-desc-ver",
+		}
+	}, {
+#endif
+		.path = "/chosen",
+		.params = {	//  <-----------26----------->
+			[SYSTAB] = "linux,uefi-system-table",
+			[MMBASE] = "linux,uefi-mmap-start",
+			[MMSIZE] = "linux,uefi-mmap-size",
+			[DCSIZE] = "linux,uefi-mmap-desc-size",
+			[DCVERS] = "linux,uefi-mmap-desc-ver",
+		}
+	}
+};
+
+static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
+				   const char *rname, void *var, int size)
+{
+	const void *prop;
+	int len;
+	u64 val;
+
+	prop = fdt_getprop(fdt, node, pname, &len);
+	if (!prop)
+		return 1;
+
+	val = (len == 4) ? (u64)be32_to_cpup(prop) : get_unaligned_be64(prop);
+
+	if (size == 8)
+		*(u64 *)var = val;
+	else
+		*(u32 *)var = (val < U32_MAX) ? val : U32_MAX; // saturate
+
+	if (efi_enabled(EFI_DBG))
+		pr_info("  %s: 0x%0*llx\n", rname, size * 2, val);
+
+	return 0;
+}
+
+u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
+{
+	const void *fdt = initial_boot_params;
+	unsigned long systab;
+	int i, j, node;
+	struct {
+		void	*var;
+		int	size;
+	} target[] = {
+		[SYSTAB] = { &systab,		sizeof(systab) },
+		[MMBASE] = { &mm->phys_map,	sizeof(mm->phys_map) },
+		[MMSIZE] = { &mm->size,		sizeof(mm->size) },
+		[DCSIZE] = { &mm->desc_size,	sizeof(mm->desc_size) },
+		[DCVERS] = { &mm->desc_version,	sizeof(mm->desc_version) },
+	};
+
+	BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(name));
+	BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(dt_params[0].params));
+
+	if (!fdt)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(dt_params); i++) {
+		node = fdt_path_offset(fdt, dt_params[i].path);
+		if (node < 0)
+			continue;
+
+		if (efi_enabled(EFI_DBG))
+			pr_info("Getting UEFI parameters from %s in DT:\n",
+				dt_params[i].path);
+
+		for (j = 0; j < ARRAY_SIZE(target); j++) {
+			const char *pname = dt_params[i].params[j];
+
+			if (!efi_get_fdt_prop(fdt, node, pname, name[j],
+					      target[j].var, target[j].size))
+				continue;
+			if (!j)
+				goto notfound;
+			pr_err("Can't find property '%s' in DT!\n", pname);
+			return 0;
+		}
+		if (dt_params[i].paravirt)
+			set_bit(EFI_PARAVIRT, &efi.flags);
+		return systab;
+	}
+notfound:
+	pr_info("UEFI not found.\n");
+	return 0;
+}