diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 32 | ||||
| -rw-r--r-- | arch/powerpc/kernel/security.c | 6 | ||||
| -rw-r--r-- | arch/powerpc/kernel/setup_64.c | 2 | ||||
| -rw-r--r-- | arch/s390/kernel/nospec-branch.c | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 11 | ||||
| -rw-r--r-- | arch/x86/mm/pti.c | 4 | ||||
| -rw-r--r-- | include/linux/cpu.h | 24 | ||||
| -rw-r--r-- | kernel/cpu.c | 15 |
8 files changed, 89 insertions, 8 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..cf82bac648cd 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2544,6 +2544,38 @@ in the "bleeding edge" mini2440 support kernel at http://repo.or.cz/w/linux-2.6/mini2440.git + mitigations= + [X86,PPC,S390] Control optional mitigations for CPU + vulnerabilities. This is a set of curated, + arch-independent options, each of which is an + aggregation of existing arch-specific options. + + off + Disable all optional CPU mitigations. This + improves system performance, but it may also + expose users to several CPU vulnerabilities. + Equivalent to: nopti [X86,PPC] + nospectre_v1 [PPC] + nobp=0 [S390] + nospectre_v2 [X86,PPC,S390] + spectre_v2_user=off [X86] + spec_store_bypass_disable=off [X86,PPC] + l1tf=off [X86] + + auto (default) + Mitigate all CPU vulnerabilities, but leave SMT + enabled, even if it's vulnerable. This is for + users who don't want to be surprised by SMT + getting disabled across kernel upgrades, or who + have other ways of avoiding SMT-based attacks. + Equivalent to: (default behavior) + + auto,nosmt + Mitigate all CPU vulnerabilities, disabling SMT + if needed. This is for users who always want to + be fully mitigated, even if it means losing SMT. + Equivalent to: l1tf=flush,nosmt [X86] + mminit_loglevel= [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this parameter allows control of the logging verbosity for diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c index b33bafb8fcea..70568ccbd9fd 100644 --- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c @@ -57,7 +57,7 @@ void setup_barrier_nospec(void) enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR); - if (!no_nospec) + if (!no_nospec && !cpu_mitigations_off()) enable_barrier_nospec(enable); } @@ -116,7 +116,7 @@ static int __init handle_nospectre_v2(char *p) early_param("nospectre_v2", handle_nospectre_v2); void setup_spectre_v2(void) { - if (no_spectrev2) + if (no_spectrev2 || cpu_mitigations_off()) do_btb_flush_fixups(); else btb_flush_enabled = true; @@ -300,7 +300,7 @@ void setup_stf_barrier(void) stf_enabled_flush_types = type; - if (!no_stf_barrier) + if (!no_stf_barrier && !cpu_mitigations_off()) stf_barrier_enable(enable); } diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index ba404dd9ce1d..4f49e1a3594c 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -932,7 +932,7 @@ void setup_rfi_flush(enum l1d_flush_type types, bool enable) enabled_flush_types = types; - if (!no_rfi_flush) + if (!no_rfi_flush && !cpu_mitigations_off()) rfi_flush_enable(enable); } diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index bdddaae96559..649135cbedd5 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/module.h> #include <linux/device.h> +#include <linux/cpu.h> #include <asm/nospec-branch.h> static int __init nobp_setup_early(char *str) @@ -58,7 +59,7 @@ early_param("nospectre_v2", nospectre_v2_setup_early); void __init nospec_auto_detect(void) { - if (test_facility(156)) { + if (test_facility(156) || cpu_mitigations_off()) { /* * The machine supports etokens. * Disable expolines and disable nobp. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 2da82eff0eb4..8043a21f36be 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -440,7 +440,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) char arg[20]; int ret, i; - if (cmdline_find_option_bool(boot_command_line, "nospectre_v2")) + if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") || + cpu_mitigations_off()) return SPECTRE_V2_CMD_NONE; ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg)); @@ -672,7 +673,8 @@ static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void) char arg[20]; int ret, i; - if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable")) { + if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") || + cpu_mitigations_off()) { return SPEC_STORE_BYPASS_CMD_NONE; } else { ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable", @@ -1008,6 +1010,11 @@ static void __init l1tf_select_mitigation(void) if (!boot_cpu_has_bug(X86_BUG_L1TF)) return; + if (cpu_mitigations_off()) + l1tf_mitigation = L1TF_MITIGATION_OFF; + else if (cpu_mitigations_auto_nosmt()) + l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT; + override_cache_bits(&boot_cpu_data); switch (l1tf_mitigation) { diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 139b28a01ce4..d0255d64edce 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -35,6 +35,7 @@ #include <linux/spinlock.h> #include <linux/mm.h> #include <linux/uaccess.h> +#include <linux/cpu.h> #include <asm/cpufeature.h> #include <asm/hypervisor.h> @@ -115,7 +116,8 @@ void __init pti_check_boottime_disable(void) } } - if (cmdline_find_option_bool(boot_command_line, "nopti")) { + if (cmdline_find_option_bool(boot_command_line, "nopti") || + cpu_mitigations_off()) { pti_mode = PTI_FORCE_OFF; pti_print_if_insecure("disabled on command line."); return; diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 5041357d0297..2d9c6f4b78f5 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -187,4 +187,28 @@ static inline void cpu_smt_disable(bool force) { } static inline void cpu_smt_check_topology(void) { } #endif +/* + * These are used for a global "mitigations=" cmdline option for toggling + * optional CPU mitigations. + */ +enum cpu_mitigations { + CPU_MITIGATIONS_OFF, + CPU_MITIGATIONS_AUTO, + CPU_MITIGATIONS_AUTO_NOSMT, +}; + +extern enum cpu_mitigations cpu_mitigations; + +/* mitigations=off */ +static inline bool cpu_mitigations_off(void) +{ + return cpu_mitigations == CPU_MITIGATIONS_OFF; +} + +/* mitigations=auto,nosmt */ +static inline bool cpu_mitigations_auto_nosmt(void) +{ + return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT; +} + #endif /* _LINUX_CPU_H_ */ diff --git a/kernel/cpu.c b/kernel/cpu.c index 6754f3ecfd94..43e741e88691 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2304,3 +2304,18 @@ void __init boot_cpu_hotplug_init(void) #endif this_cpu_write(cpuhp_state.state, CPUHP_ONLINE); } + +enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO; + +static int __init mitigations_parse_cmdline(char *arg) +{ + if (!strcmp(arg, "off")) + cpu_mitigations = CPU_MITIGATIONS_OFF; + else if (!strcmp(arg, "auto")) + cpu_mitigations = CPU_MITIGATIONS_AUTO; + else if (!strcmp(arg, "auto,nosmt")) + cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT; + + return 0; +} +early_param("mitigations", mitigations_parse_cmdline); |