linux-kernel - [PATCH 4.9 20/20] x86/speculation/mmio: Print SMT warning

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Date:   Tue, 14 Jun 2022 20:40:03 +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, Josh Poimboeuf <jpoimboe@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH 4.9 20/20] x86/speculation/mmio: Print SMT warning

From: Josh Poimboeuf <jpoimboe@...nel.org>

commit 1dc6ff02c8bf77d71b9b5d11cbc9df77cfb28626 upstream

Similar to MDS and TAA, print a warning if SMT is enabled for the MMIO
Stale Data vulnerability.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
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 |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1214,6 +1214,7 @@ static void update_mds_branch_idle(void)
 
 #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
 #define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
+#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
 
 void arch_smt_update(void)
 {
@@ -1258,6 +1259,16 @@ void arch_smt_update(void)
 		break;
 	}
 
+	switch (mmio_mitigation) {
+	case MMIO_MITIGATION_VERW:
+	case MMIO_MITIGATION_UCODE_NEEDED:
+		if (sched_smt_active())
+			pr_warn_once(MMIO_MSG_SMT);
+		break;
+	case MMIO_MITIGATION_OFF:
+		break;
+	}
+
 	mutex_unlock(&spec_ctrl_mutex);
 }