diff options
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 3ff9682d8bc4..d01dd88fae7d 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -401,6 +401,28 @@ out: cr4_clear_bits(X86_CR4_UMIP); } +static __always_inline void setup_lass(struct cpuinfo_x86 *c) +{ + if (!cpu_feature_enabled(X86_FEATURE_LASS)) + return; + + /* + * Legacy vsyscall page access causes a #GP when LASS is active. + * Disable LASS because the #GP handler doesn't support vsyscall + * emulation. + * + * Also disable LASS when running under EFI, as some runtime and + * boot services rely on 1:1 mappings in the lower half. + */ + if (IS_ENABLED(CONFIG_X86_VSYSCALL_EMULATION) || + IS_ENABLED(CONFIG_EFI)) { + setup_clear_cpu_cap(X86_FEATURE_LASS); + return; + } + + cr4_set_bits(X86_CR4_LASS); +} + /* These bits should not change their value after CPU init is finished. */ static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP | X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED; @@ -2007,10 +2029,10 @@ static void identify_cpu(struct cpuinfo_x86 *c) /* Disable the PN if appropriate */ squash_the_stupid_serial_number(c); - /* Set up SMEP/SMAP/UMIP */ setup_smep(c); setup_smap(c); setup_umip(c); + setup_lass(c); /* Enable FSGSBASE instructions if available. */ if (cpu_has(c, X86_FEATURE_FSGSBASE)) { |