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Commit aeaf7002 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent ccaabeea

arch/s390/kernel/nospec-branch.c

+11 −1
Original line number Diff line number Diff line
@@ -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.

arch/s390/kernel/nospec-sysfs.c

+2 −0
Original line number Diff line number Diff line
@@ -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))