linux-kernel - [PATCH 4.4 24/50] s390: report spectre mitigation via syslog

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Message-Id: <20180427135657.143654571@linuxfoundation.org>
Date:   Fri, 27 Apr 2018 15:58:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [PATCH 4.4 24/50] s390: report spectre mitigation via syslog

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin Schwidefsky <schwidefsky@...ibm.com>


[ 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@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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
@@ -33,6 +33,16 @@ 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);