[PATCH v2 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 unprivileged (no CPL restriction) 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/include/asm/cpufeatures.h | 2 ++
 arch/x86/kvm/cpuid.c               | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index e264758d58e2..3702d7a30ae6 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -152,6 +152,8 @@
 #define X86_FEATURE_PMM_EN		( 5*32+13) /* "pmm_en" PMM enabled */
 #define X86_FEATURE_RNG2		( 5*32+22) /* "rng2" RNG v2 */
 #define X86_FEATURE_RNG2_EN		( 5*32+23) /* "rng2_en" RNG2 enabled */
+#define X86_FEATURE_PHE2		( 5*32+25) /* "phe2" PadLock Hash Engine v2 */
+#define X86_FEATURE_PHE2_EN		( 5*32+26) /* "phe2_en" PHE2 enabled */
 
 /* More extended AMD flags: CPUID level 0x80000001, ECX, word 6 */
 #define X86_FEATURE_LAHF_LM		( 6*32+ 0) /* "lahf_lm" LAHF/SAHF in long mode */
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),
 	);
 
 	/*
-- 
2.34.1