linux-kernel - [PATCH] x86/cpuinfo: Clear X86_FEATURE_TME if TME/MKTME is disabled by BIOS

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Message-Id: <20220614210217.1940563-1-martin.fernandez@eclypsium.com>
Date:   Tue, 14 Jun 2022 18:02:17 -0300
From:   Martin Fernandez <martin.fernandez@...ypsium.com>
To:     linux-kernel@...r.kernel.org
Cc:     bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        mingo@...hat.com, tglx@...utronix.de, daniel.gutson@...ypsium.com,
        hughsient@...il.com, alex.bazhaniuk@...ypsium.com,
        Martin Fernandez <martin.fernandez@...ypsium.com>
Subject: [PATCH] x86/cpuinfo: Clear X86_FEATURE_TME if TME/MKTME is disabled by BIOS

Right now the only way to check this is by greping the kernel logs,
which is inconvinient. This is currently checked for fwupd for
example.

I understand that cpuinfo is supposed to report every feature in the
cpu but since AMD is doing the same for sme/sev I think is good to
have this for Intel too.

Signed-off-by: Martin Fernandez <martin.fernandez@...ypsium.com>
---
 arch/x86/kernel/cpu/intel.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index fd5dead8371c..7311172aceaf 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -570,6 +570,8 @@ static void detect_tme(struct cpuinfo_x86 *c)

 	if (!TME_ACTIVATE_LOCKED(tme_activate) || !TME_ACTIVATE_ENABLED(tme_activate)) {
 		pr_info_once("x86/tme: not enabled by BIOS\n");
+		if (mktme_status == MKTME_UNINITIALIZED)
+			clear_cpu_cap(c, X86_FEATURE_TME);
 		mktme_status = MKTME_DISABLED;
 		return;
 	}
--
2.30.2