Commit-ID: d68be4c4d31295ff6ae34a8ddfaa4c1a8ff42812 Gitweb: https://git.kernel.org/tip/d68be4c4d31295ff6ae34a8ddfaa4c1a8ff42812 Author: Josh Poimboeuf <jpoim...@redhat.com> AuthorDate: Fri, 12 Apr 2019 15:39:29 -0500 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Wed, 17 Apr 2019 21:37:28 +0200
x86/speculation: Support 'mitigations=' cmdline option 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 <jpoim...@redhat.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Tested-by: Jiri Kosina <jkos...@suse.cz> (on x86) Reviewed-by: Jiri Kosina <jkos...@suse.cz> Cc: Borislav Petkov <b...@alien8.de> Cc: "H . Peter Anvin" <h...@zytor.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Jiri Kosina <ji...@kernel.org> Cc: Waiman Long <long...@redhat.com> Cc: Andrea Arcangeli <aarca...@redhat.com> Cc: Jon Masters <j...@redhat.com> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> Cc: Paul Mackerras <pau...@samba.org> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: linuxppc-...@lists.ozlabs.org Cc: Martin Schwidefsky <schwidef...@de.ibm.com> Cc: Heiko Carstens <heiko.carst...@de.ibm.com> Cc: linux-s...@vger.kernel.org Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: Will Deacon <will.dea...@arm.com> Cc: linux-arm-ker...@lists.infradead.org Cc: linux-a...@vger.kernel.org Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Tyler Hicks <tyhi...@canonical.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Randy Dunlap <rdun...@infradead.org> Cc: Steven Price <steven.pr...@arm.com> Cc: Phil Auld <pa...@redhat.com> Link: https://lkml.kernel.org/r/6616d0ae169308516cfdf5216bedd169f8a8291b.1555085500.git.jpoim...@redhat.com --- Documentation/admin-guide/kernel-parameters.txt | 16 +++++++++++----- arch/x86/kernel/cpu/bugs.c | 11 +++++++++-- arch/x86/mm/pti.c | 4 +++- 3 files changed, 23 insertions(+), 8 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 720ffa9c4e04..779ddeb2929c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2514,15 +2514,20 @@ 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 @@ -2530,12 +2535,13 @@ 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 01874d54f4fd..435c078c2948 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", @@ -996,6 +998,11 @@ 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 4fee5c3003ed..5890f09bfc19 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;
