Configure s390 runtime CPU speculation bug mitigations in accordance with the 'mitigations=' cmdline option. This affects Spectre v1 and Spectre v2. The default behavior is unchanged. Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> --- Documentation/admin-guide/kernel-parameters.txt | 5 +++-- arch/s390/kernel/nospec-branch.c | 3 ++- 2 files changed, 5 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a03ab62b69af..e84a01d90e92 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2545,7 +2545,7 @@ http://repo.or.cz/w/linux-2.6/mini2440.git mitigations= - [X86,PPC] Control optional mitigations for CPU + [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. @@ -2556,7 +2556,8 @@ expose users to several CPU vulnerabilities. Equivalent to: nopti [X86,PPC] nospectre_v1 [PPC] - nospectre_v2 [X86,PPC] + nobp=0 [S390] + nospectre_v2 [X86,PPC,S390] spectre_v2_user=off [X86] spec_store_bypass_disable=off [X86,PPC] l1tf=off [X86] 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. -- 2.17.2
