Configure s390 runtime CPU speculation bug mitigations in accordance with the 'cpu_spec_mitigations=' cmdline options. 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 | 7 ++++--- arch/s390/kernel/nospec-branch.c | 4 +++- 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0e8eae1e8a25..e838af96daa4 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2554,8 +2554,9 @@ Disable all speculative CPU mitigations. Equivalent to: nopti [x86, powerpc] nospectre_v1 [powerpc] - nospectre_v2 [x86] + nospectre_v2 [x86, powerpc, s390] spectre_v2_user=off [x86] + nobp=0 [s390] spec_store_bypass_disable=off [x86, powerpc] l1tf=off [x86] @@ -2567,7 +2568,7 @@ upgrades, or who have other ways of avoiding SMT-based attacks. Equivalent to: pti=auto [x86] - spectre_v2=auto [x86] + spectre_v2=auto [x86, s390] spectre_v2_user=auto [x86] spec_store_bypass_disable=auto [x86, powerpc] l1tf=flush [x86] @@ -2578,7 +2579,7 @@ always want to be fully mitigated, even if it means losing SMT. Equivalent to: pti=auto [x86] - spectre_v2=auto [x86] + spectre_v2=auto [x86, s390] spectre_v2_user=auto [x86] spec_store_bypass_disable=auto [x86, powerpc] l1tf=flush,nosmt [x86] diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index bdddaae96559..c40eb672b43a 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 +59,8 @@ early_param("nospectre_v2", nospectre_v2_setup_early); void __init nospec_auto_detect(void) { - if (test_facility(156)) { + if (test_facility(156) || + cpu_spec_mitigations == CPU_SPEC_MITIGATIONS_OFF) { /* * The machine supports etokens. * Disable expolines and disable nobp. -- 2.17.2