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s390: report spectre mitigation via syslog 

Add a boot message if either of the spectre defenses is active.
The message is
    "Spectre V2 mitigation: execute trampolines."
or  "Spectre V2 mitigation: limited branch prediction."

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2018-03-20 16:33:43 +01:00
parent 6e179d6412
commit bc03559971
1 changed files with 10 additions and 0 deletions
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10
arch/s390/kernel/nospec-branch.c
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@ -32,6 +32,16 @@ static int __init nospec_setup_early(char *str)
}
early_param("nospec", nospec_setup_early);
static int __init nospec_report(void)
{
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))
pr_info("Spectre V2 mitigation: limited branch prediction.\n");
return 0;
}
arch_initcall(nospec_report);
#ifdef CONFIG_EXPOLINE
int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);