[PATCH 5.10 026/138] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sean Christopherson <seanjc@xxxxxxxxxx>

commit f337a6a21e2fd67eadea471e93d05dd37baaa9be upstream.

Initialize cpu_mitigations to CPU_MITIGATIONS_OFF if the kernel is built
with CONFIG_SPECULATION_MITIGATIONS=n, as the help text quite clearly
states that disabling SPECULATION_MITIGATIONS is supposed to turn off all
mitigations by default.

  │ If you say N, all mitigations will be disabled. You really
  │ 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=n.

Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs")
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Daniel Sneddon <daniel.sneddon@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240409175108.1512861-2-seanjc@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/cpu.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2600,7 +2600,8 @@ enum cpu_mitigations {
 };
 
 static enum cpu_mitigations cpu_mitigations __ro_after_init =
-	CPU_MITIGATIONS_AUTO;
+	IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) ? CPU_MITIGATIONS_AUTO :
+						     CPU_MITIGATIONS_OFF;
 
 static int __init mitigations_parse_cmdline(char *arg)
 {






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