linux-kernel - [PATCH 3/4] x86/microcode: Taint and warn on late loading

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Message-Id: <20220525161232.14924-4-bp@alien8.de>
Date:   Wed, 25 May 2022 18:12:31 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     Tony Luck <tony.luck@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/4] x86/microcode: Taint and warn on late loading

From: Borislav Petkov <bp@...e.de>

Warn before it is attempted and taint the kernel.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/cpu/microcode/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index c717db6b6856..801b44ac3851 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -493,6 +493,9 @@ static int microcode_reload_late(void)
 {
 	int ret;
 
+	pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
+	pr_err("You should switch to early loading, if possible.\n");
+
 	atomic_set(&late_cpus_in,  0);
 	atomic_set(&late_cpus_out, 0);
 
@@ -541,6 +544,8 @@ static ssize_t reload_store(struct device *dev,
 	if (ret == 0)
 		ret = size;
 
+	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+
 	return ret;
 }
 
-- 
2.35.1