Patch "x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-cpu-actually-turn-off-mitigations-by-default-for-speculation_mitigations-n.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From f337a6a21e2fd67eadea471e93d05dd37baaa9be Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Tue, 9 Apr 2024 10:51:05 -0700
Subject: x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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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
@@ -2722,7 +2722,8 @@ 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)
 {


Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are

queue-5.15/x86-cpu-actually-turn-off-mitigations-by-default-for-speculation_mitigations-n.patch




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