1 files changed, 364 insertions, 0 deletions
diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c
new file mode 100644
index 000000000000..b670fa85c61b
--- /dev/null
+++ b/arch/x86/kernel/amd_node.c
@@ -0,0 +1,364 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AMD Node helper functions and common defines
+ *
+ * Copyright (c) 2024, Advanced Micro Devices, Inc.
+ * All Rights Reserved.
+ *
+ * Author: Yazen Ghannam <Yazen.Ghannam@amd.com>
+ */
+
+#include <linux/debugfs.h>
+#include <asm/amd_node.h>
+
+/*
+ * AMD Nodes are a physical collection of I/O devices within an SoC. There can be one
+ * or more nodes per package.
+ *
+ * The nodes are software-visible through PCI config space. All nodes are enumerated
+ * on segment 0 bus 0. The device (slot) numbers range from 0x18 to 0x1F (maximum 8
+ * nodes) with 0x18 corresponding to node 0, 0x19 to node 1, etc. Each node can be a
+ * multi-function device.
+ *
+ * On legacy systems, these node devices represent integrated Northbridge functionality.
+ * On Zen-based systems, these node devices represent Data Fabric functionality.
+ *
+ * See "Configuration Space Accesses" section in BKDGs or
+ * "Processor x86 Core" -> "Configuration Space" section in PPRs.
+ */
+struct pci_dev *amd_node_get_func(u16 node, u8 func)
+{
+	if (node >= MAX_AMD_NUM_NODES)
+		return NULL;
+
+	return pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(AMD_NODE0_PCI_SLOT + node, func));
+}
+
+#define DF_BLK_INST_CNT		0x040
+#define	DF_CFG_ADDR_CNTL_LEGACY	0x084
+#define	DF_CFG_ADDR_CNTL_DF4	0xC04
+
+#define DF_MAJOR_REVISION	GENMASK(27, 24)
+
+static u16 get_cfg_addr_cntl_offset(struct pci_dev *df_f0)
+{
+	u32 reg;
+
+	/*
+	 * Revision fields added for DF4 and later.
+	 *
+	 * Major revision of '0' is found pre-DF4. Field is Read-as-Zero.
+	 */
+	if (pci_read_config_dword(df_f0, DF_BLK_INST_CNT, &reg))
+		return 0;
+
+	if (reg & DF_MAJOR_REVISION)
+		return DF_CFG_ADDR_CNTL_DF4;
+
+	return DF_CFG_ADDR_CNTL_LEGACY;
+}
+
+struct pci_dev *amd_node_get_root(u16 node)
+{
+	struct pci_dev *root;
+	u16 cntl_off;
+	u8 bus;
+
+	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
+		return NULL;
+
+	/*
+	 * D18F0xXXX [Config Address Control] (DF::CfgAddressCntl)
+	 * Bits [7:0] (SecBusNum) holds the bus number of the root device for
+	 * this Data Fabric instance. The segment, device, and function will be 0.
+	 */
+	struct pci_dev *df_f0 __free(pci_dev_put) = amd_node_get_func(node, 0);
+	if (!df_f0)
+		return NULL;
+
+	cntl_off = get_cfg_addr_cntl_offset(df_f0);
+	if (!cntl_off)
+		return NULL;
+
+	if (pci_read_config_byte(df_f0, cntl_off, &bus))
+		return NULL;
+
+	/* Grab the pointer for the actual root device instance. */
+	root = pci_get_domain_bus_and_slot(0, bus, 0);
+
+	pci_dbg(root, "is root for AMD node %u\n", node);
+	return root;
+}
+
+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
+
+#define HSMP_INDEX_OFFSET	0xc4
+#define HSMP_DATA_OFFSET	0xc8
+
+/*
+ * SMN accesses may fail in ways that are difficult to detect here in the called
+ * functions amd_smn_read() and amd_smn_write(). Therefore, callers must do
+ * their own checking based on what behavior they expect.
+ *
+ * For SMN reads, the returned value may be zero if the register is Read-as-Zero.
+ * Or it may be a "PCI Error Response", e.g. all 0xFFs. The "PCI Error Response"
+ * can be checked here, and a proper error code can be returned.
+ *
+ * But the Read-as-Zero response cannot be verified here. A value of 0 may be
+ * correct in some cases, so callers must check that this correct is for the
+ * register/fields they need.
+ *
+ * For SMN writes, success can be determined through a "write and read back"
+ * However, this is not robust when done here.
+ *
+ * Possible issues:
+ *
+ * 1) Bits that are "Write-1-to-Clear". In this case, the read value should
+ *    *not* match the write value.
+ *
+ * 2) Bits that are "Read-as-Zero"/"Writes-Ignored". This information cannot be
+ *    known here.
+ *
+ * 3) Bits that are "Reserved / Set to 1". Ditto above.
+ *
+ * Callers of amd_smn_write() should do the "write and read back" check
+ * themselves, if needed.
+ *
+ * For #1, they can see if their target bits got cleared.
+ *
+ * For #2 and #3, they can check if their target bits got set as intended.
+ *
+ * This matches what is done for RDMSR/WRMSR. As long as there's no #GP, then
+ * the operation is considered a success, and the caller does their own
+ * checking.
+ */
+static int __amd_smn_rw(u8 i_off, u8 d_off, u16 node, u32 address, u32 *value, bool write)
+{
+	struct pci_dev *root;
+	int err = -ENODEV;
+
+	if (node >= amd_num_nodes())
+		return err;
+
+	root = amd_roots[node];
+	if (!root)
+		return err;
+
+	if (!smn_exclusive)
+		return err;
+
+	guard(mutex)(&smn_mutex);
+
+	err = pci_write_config_dword(root, i_off, address);
+	if (err) {
+		pr_warn("Error programming SMN address 0x%x.\n", address);
+		return pcibios_err_to_errno(err);
+	}
+
+	err = (write ? pci_write_config_dword(root, d_off, *value)
+		     : pci_read_config_dword(root, d_off, value));
+
+	return pcibios_err_to_errno(err);
+}
+
+int __must_check amd_smn_read(u16 node, u32 address, u32 *value)
+{
+	int err = __amd_smn_rw(SMN_INDEX_OFFSET, SMN_DATA_OFFSET, node, address, value, false);
+
+	if (PCI_POSSIBLE_ERROR(*value)) {
+		err = -ENODEV;
+		*value = 0;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(amd_smn_read);
+
+int __must_check amd_smn_write(u16 node, u32 address, u32 value)
+{
+	return __amd_smn_rw(SMN_INDEX_OFFSET, SMN_DATA_OFFSET, node, address, &value, true);
+}
+EXPORT_SYMBOL_GPL(amd_smn_write);
+
+int __must_check amd_smn_hsmp_rdwr(u16 node, u32 address, u32 *value, bool write)
+{
+	return __amd_smn_rw(HSMP_INDEX_OFFSET, HSMP_DATA_OFFSET, node, address, value, write);
+}
+EXPORT_SYMBOL_GPL(amd_smn_hsmp_rdwr);
+
+static struct dentry *debugfs_dir;
+static u16 debug_node;
+static u32 debug_address;
+
+static ssize_t smn_node_write(struct file *file, const char __user *userbuf,
+			      size_t count, loff_t *ppos)
+{
+	u16 node;
+	int ret;
+
+	ret = kstrtou16_from_user(userbuf, count, 0, &node);
+	if (ret)
+		return ret;
+
+	if (node >= amd_num_nodes())
+		return -ENODEV;
+
+	debug_node = node;
+	return count;
+}
+
+static int smn_node_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "0x%08x\n", debug_node);
+	return 0;
+}
+
+static ssize_t smn_address_write(struct file *file, const char __user *userbuf,
+				 size_t count, loff_t *ppos)
+{
+	int ret;
+
+	ret = kstrtouint_from_user(userbuf, count, 0, &debug_address);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static int smn_address_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "0x%08x\n", debug_address);
+	return 0;
+}
+
+static int smn_value_show(struct seq_file *m, void *v)
+{
+	u32 val;
+	int ret;
+
+	ret = amd_smn_read(debug_node, debug_address, &val);
+	if (ret)
+		return ret;
+
+	seq_printf(m, "0x%08x\n", val);
+	return 0;
+}
+
+static ssize_t smn_value_write(struct file *file, const char __user *userbuf,
+			       size_t count, loff_t *ppos)
+{
+	u32 val;
+	int ret;
+
+	ret = kstrtouint_from_user(userbuf, count, 0, &val);
+	if (ret)
+		return ret;
+
+	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+
+	ret = amd_smn_write(debug_node, debug_address, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+DEFINE_SHOW_STORE_ATTRIBUTE(smn_node);
+DEFINE_SHOW_STORE_ATTRIBUTE(smn_address);
+DEFINE_SHOW_STORE_ATTRIBUTE(smn_value);
+
+static int amd_cache_roots(void)
+{
+	u16 node, num_nodes = amd_num_nodes();
+
+	amd_roots = kcalloc(num_nodes, sizeof(*amd_roots), GFP_KERNEL);
+	if (!amd_roots)
+		return -ENOMEM;
+
+	for (node = 0; node < num_nodes; node++)
+		amd_roots[node] = amd_node_get_root(node);
+
+	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 bool enable_dfs;
+
+static int __init amd_smn_enable_dfs(char *str)
+{
+	enable_dfs = true;
+	return 1;
+}
+__setup("amd_smn_debugfs_enable", amd_smn_enable_dfs);
+
+static int __init amd_smn_init(void)
+{
+	int err;
+
+	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
+		return 0;
+
+	guard(mutex)(&smn_mutex);
+
+	if (amd_roots)
+		return 0;
+
+	err = amd_cache_roots();
+	if (err)
+		return err;
+
+	err = reserve_root_config_spaces();
+	if (err)
+		return err;
+
+	if (enable_dfs) {
+		debugfs_dir = debugfs_create_dir("amd_smn", arch_debugfs_dir);
+
+		debugfs_create_file("node",	0600, debugfs_dir, NULL, &smn_node_fops);
+		debugfs_create_file("address",	0600, debugfs_dir, NULL, &smn_address_fops);
+		debugfs_create_file("value",	0600, debugfs_dir, NULL, &smn_value_fops);
+	}
+
+	return 0;
+}
+
+fs_initcall(amd_smn_init);