From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> commit d68be4c4d31295ff6ae34a8ddfaa4c1a8ff42812 upstream. Configure x86 runtime CPU speculation bug mitigations in accordance with the 'mitigations=' cmdline option. This affects Meltdown, Spectre v2, Speculative Store Bypass, and L1TF. The default behavior is unchanged. Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Tested-by: Jiri Kosina <jkosina@xxxxxxx> (on x86) Reviewed-by: Jiri Kosina <jkosina@xxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: "H . Peter Anvin" <hpa@xxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Jiri Kosina <jikos@xxxxxxxxxx> Cc: Waiman Long <longman@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Jon Masters <jcm@xxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: linux-s390@xxxxxxxxxxxxxxx Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-arch@xxxxxxxxxxxxxxx Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Tyler Hicks <tyhicks@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Cc: Steven Price <steven.price@xxxxxxx> Cc: Phil Auld <pauld@xxxxxxxxxx> Link: https://lkml.kernel.org/r/6616d0ae169308516cfdf5216bedd169f8a8291b.1555085500.git.jpoimboe@xxxxxxxxxx [bwh: Backported to 4.4: - Drop the auto,nosmt option and the l1tf mitigation selection, which we can't support - Adjust filenames, context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- Documentation/kernel-parameters.txt | 14 +++++++++----- arch/x86/kernel/cpu/bugs.c | 6 ++++-- arch/x86/mm/kaiser.c | 4 +++- 3 files changed, 16 insertions(+), 8 deletions(-) --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2174,15 +2174,19 @@ bytes respectively. Such letter suffixes http://repo.or.cz/w/linux-2.6/mini2440.git mitigations= - 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. + [X86] 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] + nospectre_v2 [X86] + spectre_v2_user=off [X86] + spec_store_bypass_disable=off [X86] auto (default) Mitigate all CPU vulnerabilities, but leave SMT @@ -2190,7 +2194,7 @@ bytes respectively. Such letter suffixes 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. - This is the default behavior. + Equivalent to: (default behavior) mminit_loglevel= [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -479,7 +479,8 @@ static enum spectre_v2_mitigation_cmd __ 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)); @@ -743,7 +744,8 @@ static enum ssb_mitigation_cmd __init ss 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", --- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -10,6 +10,7 @@ #include <linux/mm.h> #include <linux/uaccess.h> #include <linux/ftrace.h> +#include <linux/cpu.h> #undef pr_fmt #define pr_fmt(fmt) "Kernel/User page tables isolation: " fmt @@ -297,7 +298,8 @@ void __init kaiser_check_boottime_disabl goto skip; } - if (cmdline_find_option_bool(boot_command_line, "nopti")) + if (cmdline_find_option_bool(boot_command_line, "nopti") || + cpu_mitigations_off()) goto disable; skip:
