From: Breno Leitao <leitao@debian.org>
To: tglx@linutronix.de, bp@alien8.de,
pawan.kumar.gupta@linux.intel.com, paul@paul-moore.com
Cc: leit@meta.com, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] cpu/bugs: Disable CPU mitigations at compilation time
Date: Fri, 3 Feb 2023 04:06:15 -0800 [thread overview]
Message-ID: <20230203120615.1121272-1-leitao@debian.org> (raw)
Right now it is not possible to disable CPU vulnerabilities mitigations
at build time. Mitigation needs to be disabled passing kernel
parameters, such as 'mitigations=off'.
Create a new config option (CONFIG_CPU_MITIGATIONS_DEFAULT_OFF) that
sets the global variable `cpu_mitigations` to OFF, instead of AUTO. This
allows the creation of kernel binaries that boots with the CPU
mitigations turned off by default, and does not require dealing kernel
parameters.
Signed-off-by: Breno Leitao <leitao@debian.org>
---
kernel/cpu.c | 7 +++++--
security/Kconfig | 11 +++++++++++
2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6c0a92ca6bb5..90afb29eb62f 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2727,8 +2727,11 @@ enum cpu_mitigations {
CPU_MITIGATIONS_AUTO_NOSMT,
};
-static enum cpu_mitigations cpu_mitigations __ro_after_init =
- CPU_MITIGATIONS_AUTO;
+#ifdef CONFIG_CPU_MITIGATIONS_DEFAULT_OFF
+static enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_OFF;
+#else
+static enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO;
+#endif
static int __init mitigations_parse_cmdline(char *arg)
{
diff --git a/security/Kconfig b/security/Kconfig
index e6db09a779b7..644f91b6c26a 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -258,6 +258,17 @@ config LSM
If unsure, leave this as the default.
+config CPU_MITIGATIONS_DEFAULT_OFF
+ bool "Disable mitigations for CPU vulnerabilities by default"
+ default n
+ help
+ This option disables mitigations for CPU vulnerabilities by default.
+ Disabling CPU mitigations improves system performance,
+ but it may also expose users to several CPU vulnerabilities.
+ This option has the same effect of passing `mitigations=off` kernel
+ parameter. The CPU mitigations could be enabled back using the
+ 'mitigations' parameter.
+
source "security/Kconfig.hardening"
endmenu
--
2.30.2
next reply other threads:[~2023-02-03 12:07 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-03 12:06 Breno Leitao [this message]
2023-06-09 17:33 ` [PATCH] cpu/bugs: Disable CPU mitigations at compilation time Borislav Petkov
2023-06-12 11:22 ` David Laight
2023-06-12 11:51 ` Borislav Petkov
2023-06-12 12:16 ` David Laight
2023-06-12 13:27 ` Borislav Petkov
2023-06-10 22:37 ` Thomas Gleixner
2023-06-12 12:54 ` Breno Leitao
2023-06-12 13:32 ` Borislav Petkov
2023-06-12 13:46 ` Breno Leitao
2023-06-12 13:53 ` Borislav Petkov
2023-06-12 14:16 ` Breno Leitao
2023-06-12 16:08 ` Borislav Petkov
2023-06-12 16:37 ` Breno Leitao
2023-06-12 17:05 ` Borislav Petkov
2023-06-13 16:02 ` Breno Leitao
2023-06-13 16:20 ` Borislav Petkov
2023-06-12 17:26 ` Thomas Gleixner
2023-06-12 18:06 ` Randy Dunlap
2023-06-12 18:13 ` Borislav Petkov
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