From 1709284f082fbcb4a8e410242dcec3cc68389cda Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 12 Apr 2019 15:39:29 -0500 Subject: [PATCH] x86/speculation: Support 'mitigations=' cmdline option 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 Signed-off-by: Thomas Gleixner Tested-by: Jiri Kosina (on x86) Reviewed-by: Jiri Kosina Cc: Borislav Petkov Cc: "H . Peter Anvin" Cc: Andy Lutomirski Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Waiman Long Cc: Andrea Arcangeli Cc: Jon Masters Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: linux-s390@vger.kernel.org Cc: Catalin Marinas Cc: Will Deacon Cc: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org Cc: Greg Kroah-Hartman Cc: Tyler Hicks Cc: Linus Torvalds Cc: Randy Dunlap Cc: Steven Price Cc: Phil Auld Link: https://lkml.kernel.org/r/6616d0ae169308516cfdf5216bedd169f8a8291b.1555085500.git.jpoimboe@redhat.com [bwh: Backported to 4.9: adjust filenames, context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- Documentation/kernel-parameters.txt | 16 +++++++++++----- arch/x86/kernel/cpu/bugs.c | 11 +++++++++-- arch/x86/mm/kaiser.c | 4 +++- 3 files changed, 23 insertions(+), 8 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 23af0af..5f81df1 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2474,15 +2474,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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] + l1tf=off [X86] auto (default) Mitigate all CPU vulnerabilities, but leave SMT @@ -2490,12 +2495,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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) 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 diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index d81f55e..c2e07be 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -500,7 +500,8 @@ 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)); @@ -764,7 +765,8 @@ 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", @@ -1085,6 +1087,11 @@ 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/kaiser.c b/arch/x86/mm/kaiser.c index 3f729e2..12522db 100644 --- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -9,6 +9,7 @@ #include #include #include +#include #undef pr_fmt #define pr_fmt(fmt) "Kernel/User page tables isolation: " fmt @@ -297,7 +298,8 @@ void __init kaiser_check_boottime_disable(void) 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: -- 2.7.4