User wants to enable or disable #AC for split lock during run time. The interface /sys/kernel/debug/x86/split_lock/enable is added to allow user to control #AC for split lock and show current split lock status during run time.
Writing 1 to the file enables #AC for split lock and writing 0 disables #AC for split lock. Reading the file shows current eanbled/disabled status of #AC for split lock: 0: disabled and 1: enabled. Signed-off-by: Fenghua Yu <[email protected]> --- arch/x86/kernel/cpu/test_ctl.c | 92 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) diff --git a/arch/x86/kernel/cpu/test_ctl.c b/arch/x86/kernel/cpu/test_ctl.c index a2f84fcd4da1..e8b3032f3db0 100644 --- a/arch/x86/kernel/cpu/test_ctl.c +++ b/arch/x86/kernel/cpu/test_ctl.c @@ -17,6 +17,7 @@ #include <linux/mm.h> #include <linux/reboot.h> #include <linux/syscore_ops.h> +#include <linux/debugfs.h> #include <asm/msr.h> #define DISABLE_SPLIT_LOCK_AC 0 @@ -34,6 +35,14 @@ static DEFINE_MUTEX(reexecute_split_lock_mutex); static int split_lock_ac_kernel = DISABLE_SPLIT_LOCK_AC; static int split_lock_ac_firmware = DISABLE_SPLIT_LOCK_AC; +static DEFINE_MUTEX(split_lock_mutex); + +struct debugfs_file { + char name[32]; + int mode; + const struct file_operations *fops; +}; + /* Detete feature of #AC for split lock by probing bit 29 in MSR_TEST_CTL. */ void detect_split_lock_ac(void) { @@ -292,6 +301,85 @@ static struct syscore_ops split_lock_syscore_ops = { .resume = split_lock_bsp_resume, }; +static int enable_show(void *data, u64 *val) +{ + *val = split_lock_ac_kernel; + + return 0; +} + +static int enable_store(void *data, u64 val) +{ + u64 msr_val; + int cpu; + + if (val != DISABLE_SPLIT_LOCK_AC && val != ENABLE_SPLIT_LOCK_AC) + return -EINVAL; + + /* No need to update MSR if new setting is the same as old one. */ + if (val == split_lock_ac_kernel) + return 0; + + mutex_lock(&split_lock_mutex); + mutex_lock(&reexecute_split_lock_mutex); + + /* + * Wait until it's out of any re-executed split lock instruction + * window. + */ + wait_for_reexecution(); + + split_lock_ac_kernel = val; + /* Read split lock setting on the current CPU. */ + rdmsrl(MSR_TEST_CTL, msr_val); + /* Change the split lock setting. */ + if (split_lock_ac_kernel == DISABLE_SPLIT_LOCK_AC) + msr_val &= ~MSR_TEST_CTL_ENABLE_AC_SPLIT_LOCK; + else + msr_val |= MSR_TEST_CTL_ENABLE_AC_SPLIT_LOCK; + /* Update the split lock setting on all online CPUs. */ + for_each_online_cpu(cpu) + wrmsrl_on_cpu(cpu, MSR_TEST_CTL, msr_val); + + mutex_unlock(&reexecute_split_lock_mutex); + mutex_unlock(&split_lock_mutex); + + return 0; +} + +DEFINE_DEBUGFS_ATTRIBUTE(enable_ops, enable_show, enable_store, "%llx\n"); + +static int __init debugfs_setup_split_lock(void) +{ + struct debugfs_file debugfs_files[] = { + {"enable", 0600, &enable_ops}, + }; + struct dentry *split_lock_dir, *fd; + int i; + + split_lock_dir = debugfs_create_dir("split_lock", arch_debugfs_dir); + if (!split_lock_dir) + goto out; + + /* Create files under split_lock_dir. */ + for (i = 0; i < ARRAY_SIZE(debugfs_files); i++) { + fd = debugfs_create_file(debugfs_files[i].name, + debugfs_files[i].mode, + split_lock_dir, NULL, + debugfs_files[i].fops); + if (!fd) + goto out_cleanup; + } + + return 0; + +out_cleanup: + debugfs_remove_recursive(split_lock_dir); +out: + + return -ENOMEM; +} + static int __init split_lock_init(void) { int ret; @@ -299,6 +387,10 @@ static int __init split_lock_init(void) if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_AC)) return -ENODEV; + ret = debugfs_setup_split_lock(); + if (ret) + pr_warn("debugfs for #AC for split lock cannot be set up\n"); + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/split_lock:online", split_lock_online, split_lock_offline); if (ret < 0) -- 2.5.0
