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s390: detect etoken facility

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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>
This commit is contained in:
Martin Schwidefsky 2018-05-08 15:14:48 +02:00
parent ccaabeea02
commit aeaf7002a7
2 changed files with 13 additions and 1 deletions
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12
arch/s390/kernel/nospec-branch.c
View file

@ -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.

2
arch/s390/kernel/nospec-sysfs.c
View file

@ -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))