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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2018-05-08 15:14:48 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2018-07-18 08:32:17 +0200
commitaeaf7002a76c8da60c0f503badcbddc07650678c (patch)
tree4a8bf8d1dd9ed365d8cdb4540062f81639833ba9
parentccaabeea02026e1fbf9274800e43d9135914cd72 (diff)
downloadop-kernel-dev-aeaf7002a76c8da60c0f503badcbddc07650678c.zip
op-kernel-dev-aeaf7002a76c8da60c0f503badcbddc07650678c.tar.gz
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 <schwidefsky@de.ibm.com>
-rw-r--r--arch/s390/kernel/nospec-branch.c12
-rw-r--r--arch/s390/kernel/nospec-sysfs.c2
2 files changed, 13 insertions, 1 deletions
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
index 18ae7b9..bdddaae 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 8affad5..e30e580 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))
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