diff options
Diffstat (limited to 'arch/x86/kernel/cpu/tsx.c')
| -rw-r--r-- | arch/x86/kernel/cpu/tsx.c | 206 |
1 files changed, 148 insertions, 58 deletions
diff --git a/arch/x86/kernel/cpu/tsx.c b/arch/x86/kernel/cpu/tsx.c index 9c7a5f049292..209b5a22d880 100644 --- a/arch/x86/kernel/cpu/tsx.c +++ b/arch/x86/kernel/cpu/tsx.c @@ -11,19 +11,31 @@ #include <linux/cpufeature.h> #include <asm/cmdline.h> +#include <asm/cpu.h> +#include <asm/msr.h> #include "cpu.h" #undef pr_fmt #define pr_fmt(fmt) "tsx: " fmt -enum tsx_ctrl_states tsx_ctrl_state __ro_after_init = TSX_CTRL_NOT_SUPPORTED; +enum tsx_ctrl_states { + TSX_CTRL_AUTO, + TSX_CTRL_ENABLE, + TSX_CTRL_DISABLE, + TSX_CTRL_RTM_ALWAYS_ABORT, + TSX_CTRL_NOT_SUPPORTED, +}; -void tsx_disable(void) +static enum tsx_ctrl_states tsx_ctrl_state __ro_after_init = + IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_AUTO) ? TSX_CTRL_AUTO : + IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_OFF) ? TSX_CTRL_DISABLE : TSX_CTRL_ENABLE; + +static void tsx_disable(void) { u64 tsx; - rdmsrl(MSR_IA32_TSX_CTRL, tsx); + rdmsrq(MSR_IA32_TSX_CTRL, tsx); /* Force all transactions to immediately abort */ tsx |= TSX_CTRL_RTM_DISABLE; @@ -36,14 +48,14 @@ void tsx_disable(void) */ tsx |= TSX_CTRL_CPUID_CLEAR; - wrmsrl(MSR_IA32_TSX_CTRL, tsx); + wrmsrq(MSR_IA32_TSX_CTRL, tsx); } -void tsx_enable(void) +static void tsx_enable(void) { u64 tsx; - rdmsrl(MSR_IA32_TSX_CTRL, tsx); + rdmsrq(MSR_IA32_TSX_CTRL, tsx); /* Enable the RTM feature in the cpu */ tsx &= ~TSX_CTRL_RTM_DISABLE; @@ -55,25 +67,7 @@ void tsx_enable(void) */ tsx &= ~TSX_CTRL_CPUID_CLEAR; - wrmsrl(MSR_IA32_TSX_CTRL, tsx); -} - -static bool __init tsx_ctrl_is_supported(void) -{ - u64 ia32_cap = x86_read_arch_cap_msr(); - - /* - * TSX is controlled via MSR_IA32_TSX_CTRL. However, support for this - * MSR is enumerated by ARCH_CAP_TSX_MSR bit in MSR_IA32_ARCH_CAPABILITIES. - * - * TSX control (aka MSR_IA32_TSX_CTRL) is only available after a - * microcode update on CPUs that have their MSR_IA32_ARCH_CAPABILITIES - * bit MDS_NO=1. CPUs with MDS_NO=0 are not planned to get - * MSR_IA32_TSX_CTRL support even after a microcode update. Thus, - * tsx= cmdline requests will do nothing on CPUs without - * MSR_IA32_TSX_CTRL support. - */ - return !!(ia32_cap & ARCH_CAP_TSX_CTRL_MSR); + wrmsrq(MSR_IA32_TSX_CTRL, tsx); } static enum tsx_ctrl_states x86_get_tsx_auto_mode(void) @@ -84,7 +78,45 @@ static enum tsx_ctrl_states x86_get_tsx_auto_mode(void) return TSX_CTRL_ENABLE; } -void tsx_clear_cpuid(void) +/* + * Disabling TSX is not a trivial business. + * + * First of all, there's a CPUID bit: X86_FEATURE_RTM_ALWAYS_ABORT + * which says that TSX is practically disabled (all transactions are + * aborted by default). When that bit is set, the kernel unconditionally + * disables TSX. + * + * In order to do that, however, it needs to dance a bit: + * + * 1. The first method to disable it is through MSR_TSX_FORCE_ABORT and + * the MSR is present only when *two* CPUID bits are set: + * + * - X86_FEATURE_RTM_ALWAYS_ABORT + * - X86_FEATURE_TSX_FORCE_ABORT + * + * 2. The second method is for CPUs which do not have the above-mentioned + * MSR: those use a different MSR - MSR_IA32_TSX_CTRL and disable TSX + * through that one. Those CPUs can also have the initially mentioned + * CPUID bit X86_FEATURE_RTM_ALWAYS_ABORT set and for those the same strategy + * applies: TSX gets disabled unconditionally. + * + * When either of the two methods are present, the kernel disables TSX and + * clears the respective RTM and HLE feature flags. + * + * An additional twist in the whole thing presents late microcode loading + * which, when done, may cause for the X86_FEATURE_RTM_ALWAYS_ABORT CPUID + * bit to be set after the update. + * + * A subsequent hotplug operation on any logical CPU except the BSP will + * cause for the supported CPUID feature bits to get re-detected and, if + * RTM and HLE get cleared all of a sudden, but, userspace did consult + * them before the update, then funny explosions will happen. Long story + * short: the kernel doesn't modify CPUID feature bits after booting. + * + * That's why, this function's call in init_intel() doesn't clear the + * feature flags. + */ +static void tsx_clear_cpuid(void) { u64 msr; @@ -94,25 +126,76 @@ void tsx_clear_cpuid(void) */ if (boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT) && boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) { - rdmsrl(MSR_TSX_FORCE_ABORT, msr); + rdmsrq(MSR_TSX_FORCE_ABORT, msr); msr |= MSR_TFA_TSX_CPUID_CLEAR; - wrmsrl(MSR_TSX_FORCE_ABORT, msr); + wrmsrq(MSR_TSX_FORCE_ABORT, msr); + } else if (cpu_feature_enabled(X86_FEATURE_MSR_TSX_CTRL)) { + rdmsrq(MSR_IA32_TSX_CTRL, msr); + msr |= TSX_CTRL_CPUID_CLEAR; + wrmsrq(MSR_IA32_TSX_CTRL, msr); + } +} + +/* + * Disable TSX development mode + * + * When the microcode released in Feb 2022 is applied, TSX will be disabled by + * default on some processors. MSR 0x122 (TSX_CTRL) and MSR 0x123 + * (IA32_MCU_OPT_CTRL) can be used to re-enable TSX for development, doing so is + * not recommended for production deployments. In particular, applying MD_CLEAR + * flows for mitigation of the Intel TSX Asynchronous Abort (TAA) transient + * execution attack may not be effective on these processors when Intel TSX is + * enabled with updated microcode. + */ +static void tsx_dev_mode_disable(void) +{ + u64 mcu_opt_ctrl; + + /* Check if RTM_ALLOW exists */ + if (!boot_cpu_has_bug(X86_BUG_TAA) || + !cpu_feature_enabled(X86_FEATURE_MSR_TSX_CTRL) || + !cpu_feature_enabled(X86_FEATURE_SRBDS_CTRL)) + return; + + rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_opt_ctrl); + + if (mcu_opt_ctrl & RTM_ALLOW) { + mcu_opt_ctrl &= ~RTM_ALLOW; + wrmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_opt_ctrl); + setup_force_cpu_cap(X86_FEATURE_RTM_ALWAYS_ABORT); } } +static int __init tsx_parse_cmdline(char *str) +{ + if (!str) + return -EINVAL; + + if (!strcmp(str, "on")) { + tsx_ctrl_state = TSX_CTRL_ENABLE; + } else if (!strcmp(str, "off")) { + tsx_ctrl_state = TSX_CTRL_DISABLE; + } else if (!strcmp(str, "auto")) { + tsx_ctrl_state = TSX_CTRL_AUTO; + } else { + tsx_ctrl_state = TSX_CTRL_DISABLE; + pr_err("invalid option, defaulting to off\n"); + } + + return 0; +} +early_param("tsx", tsx_parse_cmdline); + void __init tsx_init(void) { - char arg[5] = {}; - int ret; + tsx_dev_mode_disable(); /* - * Hardware will always abort a TSX transaction if both CPUID bits - * RTM_ALWAYS_ABORT and TSX_FORCE_ABORT are set. In this case, it is - * better not to enumerate CPUID.RTM and CPUID.HLE bits. Clear them - * here. + * Hardware will always abort a TSX transaction when the CPUID bit + * RTM_ALWAYS_ABORT is set. In this case, it is better not to enumerate + * CPUID.RTM and CPUID.HLE bits. Clear them here. */ - if (boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT) && - boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) { + if (boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT)) { tsx_ctrl_state = TSX_CTRL_RTM_ALWAYS_ABORT; tsx_clear_cpuid(); setup_clear_cpu_cap(X86_FEATURE_RTM); @@ -120,32 +203,26 @@ void __init tsx_init(void) return; } - if (!tsx_ctrl_is_supported()) { + /* + * TSX is controlled via MSR_IA32_TSX_CTRL. However, support for this + * MSR is enumerated by ARCH_CAP_TSX_MSR bit in MSR_IA32_ARCH_CAPABILITIES. + * + * TSX control (aka MSR_IA32_TSX_CTRL) is only available after a + * microcode update on CPUs that have their MSR_IA32_ARCH_CAPABILITIES + * bit MDS_NO=1. CPUs with MDS_NO=0 are not planned to get + * MSR_IA32_TSX_CTRL support even after a microcode update. Thus, + * tsx= cmdline requests will do nothing on CPUs without + * MSR_IA32_TSX_CTRL support. + */ + if (x86_read_arch_cap_msr() & ARCH_CAP_TSX_CTRL_MSR) { + setup_force_cpu_cap(X86_FEATURE_MSR_TSX_CTRL); + } else { tsx_ctrl_state = TSX_CTRL_NOT_SUPPORTED; return; } - ret = cmdline_find_option(boot_command_line, "tsx", arg, sizeof(arg)); - if (ret >= 0) { - if (!strcmp(arg, "on")) { - tsx_ctrl_state = TSX_CTRL_ENABLE; - } else if (!strcmp(arg, "off")) { - tsx_ctrl_state = TSX_CTRL_DISABLE; - } else if (!strcmp(arg, "auto")) { - tsx_ctrl_state = x86_get_tsx_auto_mode(); - } else { - tsx_ctrl_state = TSX_CTRL_DISABLE; - pr_err("invalid option, defaulting to off\n"); - } - } else { - /* tsx= not provided */ - if (IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_AUTO)) - tsx_ctrl_state = x86_get_tsx_auto_mode(); - else if (IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_OFF)) - tsx_ctrl_state = TSX_CTRL_DISABLE; - else - tsx_ctrl_state = TSX_CTRL_ENABLE; - } + if (tsx_ctrl_state == TSX_CTRL_AUTO) + tsx_ctrl_state = x86_get_tsx_auto_mode(); if (tsx_ctrl_state == TSX_CTRL_DISABLE) { tsx_disable(); @@ -175,3 +252,16 @@ void __init tsx_init(void) setup_force_cpu_cap(X86_FEATURE_HLE); } } + +void tsx_ap_init(void) +{ + tsx_dev_mode_disable(); + + if (tsx_ctrl_state == TSX_CTRL_ENABLE) + tsx_enable(); + else if (tsx_ctrl_state == TSX_CTRL_DISABLE) + tsx_disable(); + else if (tsx_ctrl_state == TSX_CTRL_RTM_ALWAYS_ABORT) + /* See comment over that function for more details. */ + tsx_clear_cpuid(); +} |