diff mbox series

[RFC,v3,09/32] x86/cpu: add X86_CR4_FRED macro

Message ID 20230224070145.3572-10-xin3.li@intel.com
State New
Headers
Series x86: enable FRED for x86-64 |

Commit Message

Li, Xin3 Feb. 24, 2023, 7:01 a.m. UTC 
  From: "H. Peter Anvin (Intel)" <hpa@zytor.com>

Add X86_CR4_FRED macro for the FRED bit in %cr4. This bit should be a
pinned bit, not to be changed after initialization.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
 arch/x86/include/uapi/asm/processor-flags.h |  2 ++
 arch/x86/kernel/cpu/common.c                | 11 ++++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index c47cc7f2feeb..a90933f1ff41 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -132,6 +132,8 @@ 
 #define X86_CR4_PKE		_BITUL(X86_CR4_PKE_BIT)
 #define X86_CR4_CET_BIT		23 /* enable Control-flow Enforcement Technology */
 #define X86_CR4_CET		_BITUL(X86_CR4_CET_BIT)
+#define X86_CR4_FRED_BIT	32 /* enable FRED kernel entry */
+#define X86_CR4_FRED		_BITULL(X86_CR4_FRED_BIT)
 
 /*
  * x86-64 Task Priority Register, CR8
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 831a1a07d357..21237cb0aa93 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -412,10 +412,15 @@  static __always_inline void setup_umip(struct cpuinfo_x86 *c)
 	cr4_clear_bits(X86_CR4_UMIP);
 }
 
-/* These bits should not change their value after CPU init is finished. */
+/*
+ * These bits should not change their value after CPU init is finished.
+ * The explicit cast to unsigned long suppresses a warning on i386 for
+ * x86-64 only feature bits >= 32.
+ */
 static const unsigned long cr4_pinned_mask =
-	X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
-	X86_CR4_FSGSBASE | X86_CR4_CET;
+	(unsigned long)
+	(X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
+	 X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED);
 static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
 static unsigned long cr4_pinned_bits __ro_after_init;