diff options
Diffstat (limited to 'arch/x86/kernel/cpu/intel.c')
| -rw-r--r-- | arch/x86/kernel/cpu/intel.c | 44 |
1 files changed, 40 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 8dae51fd3db1..c1a89bc026ac 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -25,6 +25,41 @@ #include <asm/apic.h> #endif +/* + * Just in case our CPU detection goes bad, or you have a weird system, + * allow a way to override the automatic disabling of MPX. + */ +static int forcempx; + +static int __init forcempx_setup(char *__unused) +{ + forcempx = 1; + + return 1; +} +__setup("intel-skd-046-workaround=disable", forcempx_setup); + +void check_mpx_erratum(struct cpuinfo_x86 *c) +{ + if (forcempx) + return; + /* + * Turn off the MPX feature on CPUs where SMEP is not + * available or disabled. + * + * Works around Intel Erratum SKD046: "Branch Instructions + * May Initialize MPX Bound Registers Incorrectly". + * + * This might falsely disable MPX on systems without + * SMEP, like Atom processors without SMEP. But there + * is no such hardware known at the moment. + */ + if (cpu_has(c, X86_FEATURE_MPX) && !cpu_has(c, X86_FEATURE_SMEP)) { + setup_clear_cpu_cap(X86_FEATURE_MPX); + pr_warn("x86/mpx: Disabling MPX since SMEP not present\n"); + } +} + static void early_init_intel(struct cpuinfo_x86 *c) { u64 misc_enable; @@ -173,6 +208,8 @@ static void early_init_intel(struct cpuinfo_x86 *c) if (edx & (1U << 28)) c->x86_coreid_bits = get_count_order((ebx >> 16) & 0xff); } + + check_mpx_erratum(c); } #ifdef CONFIG_X86_32 @@ -263,15 +300,14 @@ static void intel_workarounds(struct cpuinfo_x86 *c) } /* - * P4 Xeon errata 037 workaround. + * P4 Xeon erratum 037 workaround. * Hardware prefetcher may cause stale data to be loaded into the cache. */ if ((c->x86 == 15) && (c->x86_model == 1) && (c->x86_mask == 1)) { if (msr_set_bit(MSR_IA32_MISC_ENABLE, - MSR_IA32_MISC_ENABLE_PREFETCH_DISABLE_BIT) - > 0) { + MSR_IA32_MISC_ENABLE_PREFETCH_DISABLE_BIT) > 0) { pr_info("CPU: C0 stepping P4 Xeon detected.\n"); - pr_info("CPU: Disabling hardware prefetching (Errata 037)\n"); + pr_info("CPU: Disabling hardware prefetching (Erratum 037)\n"); } } |