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Reply-To: Sean Christopherson <seanjc@google.com>
Date: Tue,  9 Apr 2024 10:51:05 -0700
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Subject: [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n
From: Sean Christopherson <seanjc@google.com>
To: Jonathan Corbet <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, 
	Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, 
	Peter Zijlstra <peterz@infradead.org>, Josh Poimboeuf <jpoimboe@kernel.org>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, 
	Sean Christopherson <seanjc@google.com>, Pawan Gupta <pawan.kumar.gupta@linux.intel.com>, 
	Daniel Sneddon <daniel.sneddon@linux.intel.com>
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Initialize cpu_mitigations to CPU_MITIGATIONS_OFF if the kernel is built
with CONFIG_SPECULATION_MITIGATIONS=3Dn, as the help text quite clearly
states that disabling SPECULATION_MITIGATIONS is supposed to turn off all
mitigations by default.

  =E2=94=82 If you say N, all mitigations will be disabled. You really
  =E2=94=82 should know what you are doing to say so.

As is, the kernel still defaults to CPU_MITIGATIONS_AUTO, which results in
some mitigations being enabled in spite of SPECULATION_MITIGATIONS=3Dn.

Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 kernel/cpu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 8f6affd051f7..07ad53b7f119 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -3207,7 +3207,8 @@ enum cpu_mitigations {
 };
=20
 static enum cpu_mitigations cpu_mitigations __ro_after_init =3D
-	CPU_MITIGATIONS_AUTO;
+	IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) ? CPU_MITIGATIONS_AUTO :
+						     CPU_MITIGATIONS_OFF;
=20
 static int __init mitigations_parse_cmdline(char *arg)
 {
--=20
2.44.0.478.gd926399ef9-goog