[PATCH 4/5] KVM: x86: Expose Zhaoxin PHE2 CPUID feature

[Ewan Hai <ewandevelop@gmail.com>]

Advertise the Zhaoxin PadLock Hash Engine v2 to guests via CPUID
0xC0000001 EDX bits 25 (PHE2) and 26 (PHE2_EN). PHE2 extends the
PadLock hash family with SHA-384 and SHA-512 support per FIPS 180-3,
complementing the existing PHE feature (SHA-1 and SHA-256).

Two user-mode instructions are exposed, documented in the Zhaoxin
PadLock Instruction Reference, chapter 3 ("Hash Engine"):

  - REP XSHA384 (encoding F3 0F A6 D8, subsection 3.3)
  - REP XSHA512 (encoding F3 0F A6 E0, subsection 3.4)

Both consume software-padded 128-byte blocks (RCX = block count, RSI =
input, RDI = state) and produce hash output in the state buffer.

Both instructions are user-mode and available in all CPU modes, with no
associated MSR control. The PHE2 and PHE2_EN bits are redundant by
hardware design (set or cleared together) and both serve purely as
CPUID-level feature-presence reporting flags requiring no KVM
emulation. Both bits are advertised because different software may
probe either one when checking for PHE2 availability.

Signed-off-by: Ewan Hai <ewandevelop@gmail.com>
---
 arch/x86/kvm/cpuid.c         | 2 ++
 arch/x86/kvm/reverse_cpuid.h | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 087c41341240..3fb81f7a6107 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1288,6 +1288,8 @@ void kvm_initialize_cpu_caps(void)
 		F(PMM_EN),
 		F(RNG2),
 		F(RNG2_EN),
+		F(PHE2),
+		F(PHE2_EN),
 	);
 
 	/*
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 859ba43126d8..f28300c2d5e0 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -83,6 +83,8 @@
 #define X86_FEATURE_CCS_EN		KVM_X86_FEATURE(CPUID_C000_0001_EDX, 5)
 #define X86_FEATURE_RNG2		KVM_X86_FEATURE(CPUID_C000_0001_EDX, 22)
 #define X86_FEATURE_RNG2_EN		KVM_X86_FEATURE(CPUID_C000_0001_EDX, 23)
+#define X86_FEATURE_PHE2		KVM_X86_FEATURE(CPUID_C000_0001_EDX, 25)
+#define X86_FEATURE_PHE2_EN		KVM_X86_FEATURE(CPUID_C000_0001_EDX, 26)
 
 struct cpuid_reg {
 	u32 function;
-- 
2.34.1