diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c
index 65045f223c10..ac571948cb35 100644
--- a/arch/x86/kernel/amd_node.c
+++ b/arch/x86/kernel/amd_node.c
@@ -93,6 +93,7 @@ static struct pci_dev **amd_roots;
 
 /* Protect the PCI config register pairs used for SMN. */
 static DEFINE_MUTEX(smn_mutex);
+static bool smn_exclusive;
 
 #define SMN_INDEX_OFFSET	0x60
 #define SMN_DATA_OFFSET		0x64
@@ -149,6 +150,9 @@ static int __amd_smn_rw(u8 i_off, u8 d_off, u16 node, u32 address, u32 *value, b
 	if (!root)
 		return err;
 
+	if (!smn_exclusive)
+		return err;
+
 	guard(mutex)(&smn_mutex);
 
 	err = pci_write_config_dword(root, i_off, address);
@@ -202,6 +206,39 @@ static int amd_cache_roots(void)
 	return 0;
 }
 
+static int reserve_root_config_spaces(void)
+{
+	struct pci_dev *root = NULL;
+	struct pci_bus *bus = NULL;
+
+	while ((bus = pci_find_next_bus(bus))) {
+		/* Root device is Device 0 Function 0 on each Primary Bus. */
+		root = pci_get_slot(bus, 0);
+		if (!root)
+			continue;
+
+		if (root->vendor != PCI_VENDOR_ID_AMD &&
+		    root->vendor != PCI_VENDOR_ID_HYGON)
+			continue;
+
+		pci_dbg(root, "Reserving PCI config space\n");
+
+		/*
+		 * There are a few SMN index/data pairs and other registers
+		 * that shouldn't be accessed by user space.
+		 * So reserve the entire PCI config space for simplicity rather
+		 * than covering specific registers piecemeal.
+		 */
+		if (!pci_request_config_region_exclusive(root, 0, PCI_CFG_SPACE_SIZE, NULL)) {
+			pci_err(root, "Failed to reserve config space\n");
+			return -EEXIST;
+		}
+	}
+
+	smn_exclusive = true;
+	return 0;
+}
+
 static int __init amd_smn_init(void)
 {
 	int err;
@@ -218,6 +255,10 @@ static int __init amd_smn_init(void)
 	if (err)
 		return err;
 
+	err = reserve_root_config_spaces();
+	if (err)
+		return err;
+
 	return 0;
 }