[v9,02/14] x86/cpufeature: Enumerate Key Locker feature

Commit Message

Chang S. Bae March 29, 2024, 1:53 a.m. UTC

Key Locker is a CPU feature to minimize exposure of clear-text key
material. An encoded form, called 'key handle', is referenced for data
encryption or decryption instead of accessing the clear text key.

A wrapping key loaded in the CPU's software-inaccessible state is used
to transform a user key into a key handle. On rarely unexpected
hardware failure, the key could be lost.

Here enumerate this hardware capability. It will not be shown up in
/proc/cpuinfo as userspace usage is not supported. This is because
there is no ABI to coordinate the wrapping-key failure.

The feature supports Advanced Encryption Standard (AES) cipher
algorithm with new SIMD instruction set like its predecessor (AES-NI).
Mark the feature having dependency on XMM2 like AES-NI has. The new AES
implementation will be in the crypto library.

Add X86_FEATURE_KEYLOCKER to the disabled feature list. It will be
enabled by a new Kconfig option.

Signed-off-by: Chang S. Bae <[e-mail]>
Reviewed-by: Dan Williams <[e-mail]>
---
Changes from v6:
* Massage the changelog -- re-organize the change descriptions

Changes from RFC v2:
* Do not publish the feature flag to userspace.
* Update the changelog.

Changes from RFC v1:
* Updated the changelog.
---
 arch/x86/include/asm/cpufeatures.h          | 1 +
 arch/x86/include/asm/disabled-features.h    | 8 +++++++-
 arch/x86/include/uapi/asm/processor-flags.h | 2 ++
 arch/x86/kernel/cpu/cpuid-deps.c            | 1 +
 4 files changed, 11 insertions(+), 1 deletion(-)

Patch

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index f0337f7bcf16..dd30435af487 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -399,6 +399,7 @@ 
 #define X86_FEATURE_AVX512_VPOPCNTDQ	(16*32+14) /* POPCNT for vectors of DW/QW */
 #define X86_FEATURE_LA57		(16*32+16) /* 5-level page tables */
 #define X86_FEATURE_RDPID		(16*32+22) /* RDPID instruction */
+#define X86_FEATURE_KEYLOCKER		(16*32+23) /* "" Key Locker */
 #define X86_FEATURE_BUS_LOCK_DETECT	(16*32+24) /* Bus Lock detect */
 #define X86_FEATURE_CLDEMOTE		(16*32+25) /* CLDEMOTE instruction */
 #define X86_FEATURE_MOVDIRI		(16*32+27) /* MOVDIRI instruction */
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index da4054fbf533..14aa6dc3b846 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -38,6 +38,12 @@ 
 # define DISABLE_OSPKE		(1<<(X86_FEATURE_OSPKE & 31))
 #endif /* CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS */
 
+#ifdef CONFIG_X86_KEYLOCKER
+# define DISABLE_KEYLOCKER	0
+#else
+# define DISABLE_KEYLOCKER	(1<<(X86_FEATURE_KEYLOCKER & 31))
+#endif /* CONFIG_X86_KEYLOCKER */
+
 #ifdef CONFIG_X86_5LEVEL
 # define DISABLE_LA57	0
 #else
@@ -150,7 +156,7 @@ 
 #define DISABLED_MASK14	0
 #define DISABLED_MASK15	0
 #define DISABLED_MASK16	(DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP| \
-			 DISABLE_ENQCMD)
+			 DISABLE_ENQCMD|DISABLE_KEYLOCKER)
 #define DISABLED_MASK17	0
 #define DISABLED_MASK18	(DISABLE_IBT)
 #define DISABLED_MASK19	(DISABLE_SEV_SNP)
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index f1a4adc78272..a24f7cb2cd68 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -128,6 +128,8 @@ 
 #define X86_CR4_PCIDE		_BITUL(X86_CR4_PCIDE_BIT)
 #define X86_CR4_OSXSAVE_BIT	18 /* enable xsave and xrestore */
 #define X86_CR4_OSXSAVE		_BITUL(X86_CR4_OSXSAVE_BIT)
+#define X86_CR4_KEYLOCKER_BIT	19 /* enable Key Locker */
+#define X86_CR4_KEYLOCKER	_BITUL(X86_CR4_KEYLOCKER_BIT)
 #define X86_CR4_SMEP_BIT	20 /* enable SMEP support */
 #define X86_CR4_SMEP		_BITUL(X86_CR4_SMEP_BIT)
 #define X86_CR4_SMAP_BIT	21 /* enable SMAP support */
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index b7174209d855..820dcf35eca9 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -84,6 +84,7 @@  static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_SHSTK,			X86_FEATURE_XSAVES    },
 	{ X86_FEATURE_FRED,			X86_FEATURE_LKGS      },
 	{ X86_FEATURE_FRED,			X86_FEATURE_WRMSRNS   },
+	{ X86_FEATURE_KEYLOCKER,		X86_FEATURE_XMM2      },
 	{}
 };