linux-kernel - [PATCH v2 2/2] x86/speculation: Fix redundant MDS mitigation message

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Message-Id: <20191115161445.30809-3-longman@redhat.com>
Date:   Fri, 15 Nov 2019 11:14:45 -0500
From:   Waiman Long <longman@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v2 2/2] x86/speculation: Fix redundant MDS mitigation message

Since MDS and TAA mitigations are inter-related for processors that are
affected by both vulnerabilities, the followiing confusing messages can
be printed in the kernel log:

  MDS: Vulnerable
  MDS: Mitigation: Clear CPU buffers

To avoid the first incorrect message, the printing of MDS mitigation
is now deferred after the TAA mitigation selection has been done.
However, that has the side effect of printing TAA mitigation first
before MDS mitigation.

Suggested-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Signed-off-by: Waiman Long <longman@...hat.com>
---
 arch/x86/kernel/cpu/bugs.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index cb513eaa0df1..5966a52b359f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -39,6 +39,7 @@ static void __init spectre_v2_select_mitigation(void);
 static void __init ssb_select_mitigation(void);
 static void __init l1tf_select_mitigation(void);
 static void __init mds_select_mitigation(void);
+static void __init mds_print_mitigation(void);
 static void __init taa_select_mitigation(void);
 
 /* The base value of the SPEC_CTRL MSR that always has to be preserved. */
@@ -108,6 +109,12 @@ void __init check_bugs(void)
 	mds_select_mitigation();
 	taa_select_mitigation();
 
+	/*
+	 * As MDS and TAA mitigations are inter-related, defer printing MDS
+	 * mitigation until after TAA mitigation selection is done.
+	 */
+	mds_print_mitigation();
+
 	arch_smt_update();
 
 #ifdef CONFIG_X86_32
@@ -245,7 +252,10 @@ static void __init mds_select_mitigation(void)
 		    (mds_nosmt || cpu_mitigations_auto_nosmt()))
 			cpu_smt_disable(false);
 	}
+}
 
+static void __init mds_print_mitigation(void)
+{
 	pr_info("%s\n", mds_strings[mds_mitigation]);
 }
 
-- 
2.18.1