[RFC PATCH v2 06/11] x86/cpu: Add a config option and a chicken bit for Key Locker
From: Chang S. Bae <hidden>
Date: 2021-05-14 20:21:04
Also in:
linux-doc, lkml
Subsystem:
documentation, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Jonathan Corbet, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Add a kernel config option to enable the feature (disabled by default) at compile-time. Also, add a new command-line parameter -- 'nokeylocker' to disable the feature at boot-time. Signed-off-by: Chang S. Bae <redacted> Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- Documentation/admin-guide/kernel-parameters.txt | 2 ++ arch/x86/Kconfig | 14 ++++++++++++++ arch/x86/kernel/cpu/common.c | 16 ++++++++++++++++ 3 files changed, 32 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index cb89dbdedc46..d0afe36c1802 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt@@ -3284,6 +3284,8 @@ nohugevmalloc [PPC] Disable kernel huge vmalloc mappings. + nokeylocker [X86] Disables 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 0045e1b44190..de8eeb705ed8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig@@ -1885,6 +1885,20 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS If unsure, say y. +config X86_KEYLOCKER + prompt "Key Locker" + def_bool n + depends on CPU_SUP_INTEL + help + Key Locker is a new security feature to protect data encryption + keys for the Advanced Encryption Standard (AES) algorithm. + + When enabled, every CPU has a unique internal key to wrap AES + keys in an encoded format. The internal key is not accessible + to software once loaded. + + If unsure, say y. + 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 2e64371acb81..c655cce30c2b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c@@ -353,6 +353,22 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) /* These bits should not change their value after CPU init is finished. */ static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP | X86_CR4_FSGSBASE; + +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