linux-kernel - [PATCH 4.9 12/20] x86/speculation: Add a common function for MD

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Message-Id: <20220614183724.941735289@linuxfoundation.org>
Date:   Tue, 14 Jun 2022 20:39:55 +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,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH 4.9 12/20] x86/speculation: Add a common function for MD_CLEAR mitigation update

From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>

commit f52ea6c26953fed339aa4eae717ee5c2133c7ff2 upstream

Processor MMIO Stale Data mitigation uses similar mitigation as MDS and
TAA. In preparation for adding its mitigation, add a common function to
update all mitigations that depend on MD_CLEAR.

  [ bp: Add a newline in md_clear_update_mitigation() to separate
    statements better. ]

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kernel/cpu/bugs.c |   59 +++++++++++++++++++++++++--------------------
 1 file changed, 33 insertions(+), 26 deletions(-)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -39,7 +39,7 @@ static void __init spectre_v2_select_mit
 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 md_clear_update_mitigation(void);
 static void __init taa_select_mitigation(void);
 static void __init srbds_select_mitigation(void);
 
@@ -112,10 +112,10 @@ void __init check_bugs(void)
 	srbds_select_mitigation();
 
 	/*
-	 * As MDS and TAA mitigations are inter-related, print MDS
-	 * mitigation until after TAA mitigation selection is done.
+	 * As MDS and TAA mitigations are inter-related, update and print their
+	 * mitigation after TAA mitigation selection is done.
 	 */
-	mds_print_mitigation();
+	md_clear_update_mitigation();
 
 	arch_smt_update();
 
@@ -256,14 +256,6 @@ static void __init mds_select_mitigation
 	}
 }
 
-static void __init mds_print_mitigation(void)
-{
-	if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off())
-		return;
-
-	pr_info("%s\n", mds_strings[mds_mitigation]);
-}
-
 static int __init mds_cmdline(char *str)
 {
 	if (!boot_cpu_has_bug(X86_BUG_MDS))
@@ -311,7 +303,7 @@ static void __init taa_select_mitigation
 	/* TSX previously disabled by tsx=off */
 	if (!boot_cpu_has(X86_FEATURE_RTM)) {
 		taa_mitigation = TAA_MITIGATION_TSX_DISABLED;
-		goto out;
+		return;
 	}
 
 	if (cpu_mitigations_off()) {
@@ -325,7 +317,7 @@ static void __init taa_select_mitigation
 	 */
 	if (taa_mitigation == TAA_MITIGATION_OFF &&
 	    mds_mitigation == MDS_MITIGATION_OFF)
-		goto out;
+		return;
 
 	if (boot_cpu_has(X86_FEATURE_MD_CLEAR))
 		taa_mitigation = TAA_MITIGATION_VERW;
@@ -357,18 +349,6 @@ static void __init taa_select_mitigation
 
 	if (taa_nosmt || cpu_mitigations_auto_nosmt())
 		cpu_smt_disable(false);
-
-	/*
-	 * Update MDS mitigation, if necessary, as the mds_user_clear is
-	 * now enabled for TAA mitigation.
-	 */
-	if (mds_mitigation == MDS_MITIGATION_OFF &&
-	    boot_cpu_has_bug(X86_BUG_MDS)) {
-		mds_mitigation = MDS_MITIGATION_FULL;
-		mds_select_mitigation();
-	}
-out:
-	pr_info("%s\n", taa_strings[taa_mitigation]);
 }
 
 static int __init tsx_async_abort_parse_cmdline(char *str)
@@ -393,6 +373,33 @@ static int __init tsx_async_abort_parse_
 early_param("tsx_async_abort", tsx_async_abort_parse_cmdline);
 
 #undef pr_fmt
+#define pr_fmt(fmt)     "" fmt
+
+static void __init md_clear_update_mitigation(void)
+{
+	if (cpu_mitigations_off())
+		return;
+
+	if (!static_key_enabled(&mds_user_clear))
+		goto out;
+
+	/*
+	 * mds_user_clear is now enabled. Update MDS mitigation, if
+	 * necessary.
+	 */
+	if (mds_mitigation == MDS_MITIGATION_OFF &&
+	    boot_cpu_has_bug(X86_BUG_MDS)) {
+		mds_mitigation = MDS_MITIGATION_FULL;
+		mds_select_mitigation();
+	}
+out:
+	if (boot_cpu_has_bug(X86_BUG_MDS))
+		pr_info("MDS: %s\n", mds_strings[mds_mitigation]);
+	if (boot_cpu_has_bug(X86_BUG_TAA))
+		pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
+}
+
+#undef pr_fmt
 #define pr_fmt(fmt)	"SRBDS: " fmt
 
 enum srbds_mitigations {