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
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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
