diff options
| -rw-r--r-- | arch/arm64/include/asm/cpufeature.h | 9 | ||||
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 16 |
2 files changed, 20 insertions, 5 deletions
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 09825b667af0..96c99b201b2f 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -244,6 +244,15 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \ ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) +/* + * CPU feature detected at boot time, on one or more CPUs. A late CPU + * is not allowed to have the capability when the system doesn't have it. + * It is Ok for a late CPU to miss the feature. + */ +#define ARM64_CPUCAP_BOOT_RESTRICTED_CPU_LOCAL_FEATURE \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU) + struct arm64_cpu_capabilities { const char *desc; u16 capability; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 439cdca71024..b3ebbc56bebb 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -824,10 +824,9 @@ static bool has_no_fpsimd(const struct arm64_cpu_capabilities *entry, int __unus static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, - int __unused) + int scope) { char const *str = "command line option"; - u64 pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); /* * For reasons that aren't entirely clear, enabling KPTI on Cavium @@ -863,8 +862,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, } /* Defer to CPU feature registers */ - return !cpuid_feature_extract_unsigned_field(pfr0, - ID_AA64PFR0_CSV3_SHIFT); + return !has_cpuid_feature(entry, scope); } static void @@ -1011,7 +1009,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = { { .desc = "Kernel page table isolation (KPTI)", .capability = ARM64_UNMAP_KERNEL_AT_EL0, - .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .type = ARM64_CPUCAP_BOOT_RESTRICTED_CPU_LOCAL_FEATURE, + /* + * The ID feature fields below are used to indicate that + * the CPU doesn't need KPTI. See unmap_kernel_at_el0 for + * more details. + */ + .sys_reg = SYS_ID_AA64PFR0_EL1, + .field_pos = ID_AA64PFR0_CSV3_SHIFT, + .min_field_value = 1, .matches = unmap_kernel_at_el0, .cpu_enable = kpti_install_ng_mappings, }, |