From aeaf7002a76c8da60c0f503badcbddc07650678c Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 8 May 2018 15:14:48 +0200 Subject: [PATCH] s390: detect etoken facility Detect and report the etoken facility. With spectre_v2=auto or CONFIG_EXPOLINE_AUTO=y automatically disable expolines and use the full branch prediction mode for the kernel. Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/nospec-branch.c | 12 +++++++++++- arch/s390/kernel/nospec-sysfs.c | 2 ++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 18ae7b9c71d6..bdddaae96559 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -35,6 +35,8 @@ early_param("nospec", nospec_setup_early); static int __init nospec_report(void) { + if (test_facility(156)) + pr_info("Spectre V2 mitigation: etokens\n"); if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) pr_info("Spectre V2 mitigation: execute trampolines\n"); if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) @@ -56,7 +58,15 @@ early_param("nospectre_v2", nospectre_v2_setup_early); void __init nospec_auto_detect(void) { - if (IS_ENABLED(CC_USING_EXPOLINE)) { + if (test_facility(156)) { + /* + * The machine supports etokens. + * Disable expolines and disable nobp. + */ + if (IS_ENABLED(CC_USING_EXPOLINE)) + nospec_disable = 1; + __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + } else if (IS_ENABLED(CC_USING_EXPOLINE)) { /* * The kernel has been compiled with expolines. * Keep expolines enabled and disable nobp. diff --git a/arch/s390/kernel/nospec-sysfs.c b/arch/s390/kernel/nospec-sysfs.c index 8affad5f18cb..e30e580ae362 100644 --- a/arch/s390/kernel/nospec-sysfs.c +++ b/arch/s390/kernel/nospec-sysfs.c @@ -13,6 +13,8 @@ ssize_t cpu_show_spectre_v1(struct device *dev, ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf) { + if (test_facility(156)) + return sprintf(buf, "Mitigation: etokens\n"); if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) return sprintf(buf, "Mitigation: execute trampolines\n"); if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) -- GitLab