diff options
Diffstat (limited to 'arch/x86/kernel/cpu/intel.c')
| -rw-r--r-- | arch/x86/kernel/cpu/intel.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index be82cd5841c3..a19a680542ce 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -19,6 +19,9 @@ #include <asm/microcode_intel.h> #include <asm/hwcap2.h> #include <asm/elf.h> +#include <asm/cpu_device_id.h> +#include <asm/cmdline.h> +#include <asm/traps.h> #ifdef CONFIG_X86_64 #include <linux/topology.h> @@ -31,6 +34,20 @@ #include <asm/apic.h> #endif +enum split_lock_detect_state { + sld_off = 0, + sld_warn, + sld_fatal, +}; + +/* + * Default to sld_off because most systems do not support split lock detection + * split_lock_setup() will switch this to sld_warn on systems that support + * split lock detect, unless there is a command line override. + */ +static enum split_lock_detect_state sld_state __ro_after_init = sld_off; +static u64 msr_test_ctrl_cache __ro_after_init; + /* * Processors which have self-snooping capability can handle conflicting * memory type across CPUs by snooping its own cache. However, there exists @@ -570,6 +587,8 @@ static void init_intel_misc_features(struct cpuinfo_x86 *c) wrmsrl(MSR_MISC_FEATURES_ENABLES, msr); } +static void split_lock_init(void); + static void init_intel(struct cpuinfo_x86 *c) { early_init_intel(c); @@ -684,6 +703,8 @@ static void init_intel(struct cpuinfo_x86 *c) tsx_enable(); if (tsx_ctrl_state == TSX_CTRL_DISABLE) tsx_disable(); + + split_lock_init(); } #ifdef CONFIG_X86_32 @@ -945,3 +966,206 @@ static const struct cpu_dev intel_cpu_dev = { }; cpu_dev_register(intel_cpu_dev); + +#undef pr_fmt +#define pr_fmt(fmt) "x86/split lock detection: " fmt + +static const struct { + const char *option; + enum split_lock_detect_state state; +} sld_options[] __initconst = { + { "off", sld_off }, + { "warn", sld_warn }, + { "fatal", sld_fatal }, +}; + +static inline bool match_option(const char *arg, int arglen, const char *opt) +{ + int len = strlen(opt); + + return len == arglen && !strncmp(arg, opt, len); +} + +static bool split_lock_verify_msr(bool on) +{ + u64 ctrl, tmp; + + if (rdmsrl_safe(MSR_TEST_CTRL, &ctrl)) + return false; + if (on) + ctrl |= MSR_TEST_CTRL_SPLIT_LOCK_DETECT; + else + ctrl &= ~MSR_TEST_CTRL_SPLIT_LOCK_DETECT; + if (wrmsrl_safe(MSR_TEST_CTRL, ctrl)) + return false; + rdmsrl(MSR_TEST_CTRL, tmp); + return ctrl == tmp; +} + +static void __init split_lock_setup(void) +{ + enum split_lock_detect_state state = sld_warn; + char arg[20]; + int i, ret; + + if (!split_lock_verify_msr(false)) { + pr_info("MSR access failed: Disabled\n"); + return; + } + + ret = cmdline_find_option(boot_command_line, "split_lock_detect", + arg, sizeof(arg)); + if (ret >= 0) { + for (i = 0; i < ARRAY_SIZE(sld_options); i++) { + if (match_option(arg, ret, sld_options[i].option)) { + state = sld_options[i].state; + break; + } + } + } + + switch (state) { + case sld_off: + pr_info("disabled\n"); + return; + case sld_warn: + pr_info("warning about user-space split_locks\n"); + break; + case sld_fatal: + pr_info("sending SIGBUS on user-space split_locks\n"); + break; + } + + rdmsrl(MSR_TEST_CTRL, msr_test_ctrl_cache); + + if (!split_lock_verify_msr(true)) { + pr_info("MSR access failed: Disabled\n"); + return; + } + + sld_state = state; + setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT); +} + +/* + * MSR_TEST_CTRL is per core, but we treat it like a per CPU MSR. Locking + * is not implemented as one thread could undo the setting of the other + * thread immediately after dropping the lock anyway. + */ +static void sld_update_msr(bool on) +{ + u64 test_ctrl_val = msr_test_ctrl_cache; + + if (on) + test_ctrl_val |= MSR_TEST_CTRL_SPLIT_LOCK_DETECT; + + wrmsrl(MSR_TEST_CTRL, test_ctrl_val); +} + +static void split_lock_init(void) +{ + split_lock_verify_msr(sld_state != sld_off); +} + +static void split_lock_warn(unsigned long ip) +{ + pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", + current->comm, current->pid, ip); + + /* + * Disable the split lock detection for this task so it can make + * progress and set TIF_SLD so the detection is re-enabled via + * switch_to_sld() when the task is scheduled out. + */ + sld_update_msr(false); + set_tsk_thread_flag(current, TIF_SLD); +} + +bool handle_guest_split_lock(unsigned long ip) +{ + if (sld_state == sld_warn) { + split_lock_warn(ip); + return true; + } + + pr_warn_once("#AC: %s/%d %s split_lock trap at address: 0x%lx\n", + current->comm, current->pid, + sld_state == sld_fatal ? "fatal" : "bogus", ip); + + current->thread.error_code = 0; + current->thread.trap_nr = X86_TRAP_AC; + force_sig_fault(SIGBUS, BUS_ADRALN, NULL); + return false; +} +EXPORT_SYMBOL_GPL(handle_guest_split_lock); + +bool handle_user_split_lock(struct pt_regs *regs, long error_code) +{ + if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) + return false; + split_lock_warn(regs->ip); + return true; +} + +/* + * This function is called only when switching between tasks with + * different split-lock detection modes. It sets the MSR for the + * mode of the new task. This is right most of the time, but since + * the MSR is shared by hyperthreads on a physical core there can + * be glitches when the two threads need different modes. + */ +void switch_to_sld(unsigned long tifn) +{ + sld_update_msr(!(tifn & _TIF_SLD)); +} + +/* + * Bits in the IA32_CORE_CAPABILITIES are not architectural, so they should + * only be trusted if it is confirmed that a CPU model implements a + * specific feature at a particular bit position. + * + * The possible driver data field values: + * + * - 0: CPU models that are known to have the per-core split-lock detection + * feature even though they do not enumerate IA32_CORE_CAPABILITIES. + * + * - 1: CPU models which may enumerate IA32_CORE_CAPABILITIES and if so use + * bit 5 to enumerate the per-core split-lock detection feature. + */ +static const struct x86_cpu_id split_lock_cpu_ids[] __initconst = { + X86_MATCH_INTEL_FAM6_MODEL(ICELAKE_X, 0), + X86_MATCH_INTEL_FAM6_MODEL(ICELAKE_L, 0), + X86_MATCH_INTEL_FAM6_MODEL(ATOM_TREMONT, 1), + X86_MATCH_INTEL_FAM6_MODEL(ATOM_TREMONT_D, 1), + X86_MATCH_INTEL_FAM6_MODEL(ATOM_TREMONT_L, 1), + {} +}; + +void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) +{ + const struct x86_cpu_id *m; + u64 ia32_core_caps; + + if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) + return; + + m = x86_match_cpu(split_lock_cpu_ids); + if (!m) + return; + + switch (m->driver_data) { + case 0: + break; + case 1: + if (!cpu_has(c, X86_FEATURE_CORE_CAPABILITIES)) + return; + rdmsrl(MSR_IA32_CORE_CAPS, ia32_core_caps); + if (!(ia32_core_caps & MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT)) + return; + break; + default: + return; + } + + split_lock_setup(); +} |