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

[Chang S. Bae]

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@xxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
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