[RFC PATCH v3 20/27] KVM: x86: Add reverse-CPUID lookup support for scattered SGX features

Kai Huang
2021-01-26T15:20:15Z

From: Sean Christopherson <seanjc@google.com>

Define a new KVM-only feature word for advertising and querying SGX
sub-features in CPUID.0x12.0x0.EAX. Because SGX1 and SGX2 are scattered
in the kernel's feature word, they need to be translated so that the
bit numbers match those of hardware.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---
arch/x86/kvm/cpuid.h | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 2041e2f07347..f55701ef58fc 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -13,13 +13,18 @@
* "bug" caps, but KVM doesn't use those.
*/
enum kvm_only_cpuid_leafs {
- NR_KVM_CPU_CAPS = NCAPINTS,
+ CPUID_12_EAX = NCAPINTS,
+ NR_KVM_CPU_CAPS,

NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
};

#define X86_KVM_FEATURE(w, f) ((w)*32 + (f))

+/* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
+#define __X86_FEATURE_SGX1 X86_KVM_FEATURE(CPUID_12_EAX, 0)
+#define __X86_FEATURE_SGX2 X86_KVM_FEATURE(CPUID_12_EAX, 1)
+
extern u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
void kvm_set_cpu_caps(void);

@@ -76,6 +81,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
[CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
[CPUID_7_EDX] = { 7, 0, CPUID_EDX},
[CPUID_7_1_EAX] = { 7, 1, CPUID_EAX},
+ [CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX},
};

/*
@@ -102,6 +108,11 @@ static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
*/
static __always_inline u32 __feature_translate(int x86_feature)
{
+ if (x86_feature == X86_FEATURE_SGX1)
+ return __X86_FEATURE_SGX1;
+ else if (x86_feature == X86_FEATURE_SGX2)
+ return __X86_FEATURE_SGX2;
+
return x86_feature;
}

--
2.29.2