[PATCH v6 09/12] x86/cpu: Add a configuration and command line option for Key Locker

Chang S. Bae
2023-04-10T23:12:19Z

Add CONFIG_X86_KEYLOCKER to gate whether Key Locker is initialized at boot.
The option is selected by the Key Locker cipher module CRYPTO_AES_KL (to be
added in a later patch).

Add a new command line option "nokeylocker" to optionally override the
default CONFIG_X86_KEYLOCKER=y behavior.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes from RFC v2:
* Make the option selected by CRYPTO_AES_KL. (Dan Williams)
* Massage the changelog and the config option description.
---
Documentation/admin-guide/kernel-parameters.txt | 2 ++
arch/x86/Kconfig | 3 +++
arch/x86/kernel/cpu/common.c | 16 ++++++++++++++++
3 files changed, 21 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 5f2ec4b0f927..6534e6217e56 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3655,6 +3655,8 @@

nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.

+ nokeylocker [X86] Disable Key Locker hardware feature.
+
nosmt [KNL,S390] Disable symmetric multithreading (SMT).
Equivalent to smt=1.

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c94297369448..91f2063ab283 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1894,6 +1894,9 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS

If unsure, say y.

+config X86_KEYLOCKER
+ bool
+
choice
prompt "TSX enable mode"
depends on CPU_SUP_INTEL
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a1edd5997e0a..c5550b8f030d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -419,6 +419,22 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
static const unsigned long cr4_pinned_mask =
X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
X86_CR4_FSGSBASE | X86_CR4_CET;
+
+static __init int x86_nokeylocker_setup(char *arg)
+{
+ /* Expect an exact match without trailing characters. */
+ if (strlen(arg))
+ return 0;
+
+ if (!cpu_feature_enabled(X86_FEATURE_KEYLOCKER))
+ return 1;
+
+ setup_clear_cpu_cap(X86_FEATURE_KEYLOCKER);
+ pr_info("x86/keylocker: Disabled by kernel command line.\n");
+ return 1;
+}
+__setup("nokeylocker", x86_nokeylocker_setup);
+
static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
static unsigned long cr4_pinned_bits __ro_after_init;

--
2.17.1