[PATCH v13 06/35] x86/cpufeatures: Add the CPU feature bit for FRED

Xin Li
2023-12-05T11:21:22Z

From: "H. Peter Anvin (Intel)" <hpa@zytor.com>

Any FRED CPU will always have the following features as its baseline:
1) LKGS, load attributes of the GS segment but the base address into
the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s descriptor
cache.
2) WRMSRNS, non-serializing WRMSR for faster MSR writes.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---

Change since v12:
* s/cpu/CPU/g (Borislav Petkov).
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kernel/cpu/cpuid-deps.c | 2 ++
tools/arch/x86/include/asm/cpufeatures.h | 1 +
3 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index a903fc130e49..fef95d190054 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -324,6 +324,7 @@
#define X86_FEATURE_FZRM (12*32+10) /* "" Fast zero-length REP MOVSB */
#define X86_FEATURE_FSRS (12*32+11) /* "" Fast short REP STOSB */
#define X86_FEATURE_FSRC (12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
+#define X86_FEATURE_FRED (12*32+17) /* Flexible Return and Event Delivery */
#define X86_FEATURE_LKGS (12*32+18) /* "" Load "kernel" (userspace) GS */
#define X86_FEATURE_WRMSRNS (12*32+19) /* "" Non-serializing WRMSR */
#define X86_FEATURE_AMX_FP16 (12*32+21) /* "" AMX fp16 Support */
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index e462c1d3800a..b7174209d855 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -82,6 +82,8 @@ static const struct cpuid_dep cpuid_deps[] = {
{ X86_FEATURE_XFD, X86_FEATURE_XGETBV1 },
{ X86_FEATURE_AMX_TILE, X86_FEATURE_XFD },
{ X86_FEATURE_SHSTK, X86_FEATURE_XSAVES },
+ { X86_FEATURE_FRED, X86_FEATURE_LKGS },
+ { X86_FEATURE_FRED, X86_FEATURE_WRMSRNS },
{}
};

diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
index 26a73ae18a86..f433e9f61354 100644
--- a/tools/arch/x86/include/asm/cpufeatures.h
+++ b/tools/arch/x86/include/asm/cpufeatures.h
@@ -321,6 +321,7 @@
#define X86_FEATURE_FZRM (12*32+10) /* "" Fast zero-length REP MOVSB */
#define X86_FEATURE_FSRS (12*32+11) /* "" Fast short REP STOSB */
#define X86_FEATURE_FSRC (12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
+#define X86_FEATURE_FRED (12*32+17) /* Flexible Return and Event Delivery */
#define X86_FEATURE_LKGS (12*32+18) /* "" Load "kernel" (userspace) GS */
#define X86_FEATURE_WRMSRNS (12*32+19) /* "" Non-serializing WRMSR */
#define X86_FEATURE_AMX_FP16 (12*32+21) /* "" AMX fp16 Support */
--
2.43.0