[PATCH v3 3/8] KVM:CPUID: Add CPUID support for Guest CET

[Yang Weijiang]

Guest CET SHSTK and IBT capability are reported via
CPUID.(EAX=7, ECX=0):ECX[bit 7] and EDX[bit 20] respectively.
Guest user mode and supervisor mode xsaves component size
is reported via CPUID.(EAX=0xD, ECX=1):ECX[bit 11] and ECX[bit 12]
respectively.

Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/kvm/cpuid.c | 60 +++++++++++++++++++++++++++++++++-----------
 arch/x86/kvm/x86.h   |  4 +++
 2 files changed, 50 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index cb1aece25b17..5e05756cc6db 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -65,6 +65,16 @@ u64 kvm_supported_xcr0(void)
 	return xcr0;
 }
 
+u64 kvm_supported_xss(void)
+{
+	u64 xss;
+
+	rdmsrl(MSR_IA32_XSS, xss);
+	xss &= KVM_SUPPORTED_XSS;
+	return xss;
+}
+EXPORT_SYMBOL(kvm_supported_xss);
+
 #define F(x) bit(X86_FEATURE_##x)
 
 /* For scattered features from cpufeatures.h; we currently expose none */
@@ -323,6 +333,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 				 u32 index, int *nent, int maxnent)
 {
 	int r;
+	u32 eax, ebx, ecx, edx;
 	unsigned f_nx = is_efer_nx() ? F(NX) : 0;
 #ifdef CONFIG_X86_64
 	unsigned f_gbpages = (kvm_x86_ops->get_lpage_level() == PT_PDPE_LEVEL)
@@ -503,6 +514,20 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			 * if the host doesn't support it.
 			 */
 			entry->edx |= F(ARCH_CAPABILITIES);
+
+			/*
+			 * Guest OS CET enabling is designed independent to
+			 * host enabling, it only has dependency on Host HW
+			 * capability, if it has, report CET support to
+			 * Guest.
+			 */
+			cpuid_count(7, 0, &eax, &ebx, &ecx, &edx);
+			if (ecx & F(SHSTK))
+				entry->ecx |= F(SHSTK);
+
+			if (edx & F(IBT))
+				entry->edx |= F(IBT);
+
 		} else {
 			entry->ebx = 0;
 			entry->ecx = 0;
@@ -564,14 +589,17 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 	}
 	case 0xd: {
 		int idx, i;
-		u64 supported = kvm_supported_xcr0();
+		u64 u_supported = kvm_supported_xcr0();
+		u64 s_supported = kvm_supported_xss();
+		u64 supported;
+		int compacted;
 
-		entry->eax &= supported;
-		entry->ebx = xstate_required_size(supported, false);
+		entry->eax &= u_supported;
+		entry->ebx = xstate_required_size(u_supported, false);
 		entry->ecx = entry->ebx;
-		entry->edx &= supported >> 32;
+		entry->edx &= u_supported >> 32;
 		entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
-		if (!supported)
+		if (!u_supported && !s_supported)
 			break;
 
 		for (idx = 1, i = 1; idx < 64; ++idx) {
@@ -583,19 +611,23 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			if (idx == 1) {
 				entry[i].eax &= kvm_cpuid_D_1_eax_x86_features;
 				cpuid_mask(&entry[i].eax, CPUID_D_1_EAX);
-				entry[i].ebx = 0;
-				if (entry[i].eax & (F(XSAVES)|F(XSAVEC)))
-					entry[i].ebx =
-						xstate_required_size(supported,
-								     true);
+				supported = u_supported | s_supported;
+				compacted = entry[i].eax &
+					(F(XSAVES) | F(XSAVEC));
+				entry[i].ebx = xstate_required_size(supported,
+								    compacted);
+				entry[i].ecx &= s_supported;
+				entry[i].edx = 0;
 			} else {
+				supported = (entry[i].ecx & 1) ? s_supported :
+								 u_supported;
 				if (entry[i].eax == 0 || !(supported & mask))
 					continue;
-				if (WARN_ON_ONCE(entry[i].ecx & 1))
-					continue;
+				entry[i].ecx &= 1;
+				entry[i].edx = 0;
+				if (entry[i].ecx)
+					entry[i].ebx = 0;
 			}
-			entry[i].ecx = 0;
-			entry[i].edx = 0;
 			entry[i].flags |=
 			       KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
 			++*nent;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 224cd0a47568..c61da41c3c5c 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -283,6 +283,10 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
 				| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
 				| XFEATURE_MASK_PKRU)
+
+#define KVM_SUPPORTED_XSS	(XFEATURE_MASK_SHSTK_USER \
+				| XFEATURE_MASK_SHSTK_KERNEL)
+
 extern u64 host_xcr0;
 
 extern u64 kvm_supported_xcr0(void);
-- 
2.17.1