4.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
[ Upstream commit bc035599718412cfba9249aa713f90ef13f13ee9 ]
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@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/kernel/nospec-branch.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -32,6 +32,16 @@ static int __init nospec_setup_early(cha
}
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);
