public-mirrors/linux
1
0
Fork 0
mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-08-05 00:34:52 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

x86/amd_node: Add support for debugfs access to SMN registers

Browse source 
There are certain registers on AMD Zen systems that can only be accessed
through SMN.

Introduce a new interface that provides debugfs files for accessing SMN.  As
this introduces the capability for userspace to manipulate the hardware in
unpredictable ways, taint the kernel when writing.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250130-wip-x86-amd-nb-cleanup-v4-3-b5cc997e471b@amd.com
This commit is contained in:
Mario Limonciello 2025-01-30 19:48:57 +00:00 • committed by Ingo Molnar
parent 8351845307
commit 9c19cc1f5f
1 changed files with 99 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

99
arch/x86/kernel/amd_node.c
View file

@ -8,6 +8,7 @@
* Author: Yazen Ghannam <Yazen.Ghannam@amd.com>
*/
#include <linux/debugfs.h>
#include <asm/amd_node.h>
/*
@ -192,6 +193,87 @@ int __must_check amd_smn_hsmp_rdwr(u16 node, u32 address, u32 *value, bool 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();
@ -239,6 +321,15 @@ static int reserve_root_config_spaces(void)
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;
@ -259,6 +350,14 @@ static int __init amd_smn_init(void)
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;
}