[PATCH] KVM: CPUID: Fix IA32_XSS support in CPUID(0xd,i) enumeration

[Yang Weijiang]

The control bits in IA32_XSS MSR are being used for new features,
but current CPUID(0xd,i) enumeration code doesn't support them, so
fix existing code first.

The supervisor states in IA32_XSS haven't been used in public
KVM code, so set KVM_SUPPORTED_XSS to 0 now, anyone who's developing
IA32_XSS related feature may expand the macro to add the CPUID support,
otherwise, CPUID(0xd,i>1) always reports 0 of the subleaf to guest.

Extracted old code into a new filter and keep it same flavor as others.

This patch passed selftest on a few Intel platforms.

Suggested-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/cpuid.c            | 94 +++++++++++++++++++++------------
 arch/x86/kvm/svm.c              |  7 +++
 arch/x86/kvm/vmx/vmx.c          |  6 +++
 arch/x86/kvm/x86.h              |  7 +++
 5 files changed, 82 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 74e88e5edd9c..d018df8c5f32 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1209,6 +1209,7 @@ struct kvm_x86_ops {
 	uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
 
 	bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu);
+	u64 (*supported_xss)(void);
 };
 
 struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 22c2720cd948..9d282fec0a62 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -62,6 +62,11 @@ u64 kvm_supported_xcr0(void)
 	return xcr0;
 }
 
+u64 kvm_supported_xss(void)
+{
+	return KVM_SUPPORTED_XSS & kvm_x86_ops->supported_xss();
+}
+
 #define F(x) bit(X86_FEATURE_##x)
 
 int kvm_update_cpuid(struct kvm_vcpu *vcpu)
@@ -414,6 +419,50 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
 	}
 }
 
+static inline void do_cpuid_0xd_mask(struct kvm_cpuid_entry2 *entry, int index)
+{
+	unsigned int f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
+	/* cpuid 0xD.1.eax */
+	const u32 kvm_cpuid_D_1_eax_x86_features =
+		F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves;
+	u64 u_supported = kvm_supported_xcr0();
+	u64 s_supported = kvm_supported_xss();
+	u64 supported;
+
+	switch (index) {
+	case 0:
+		entry->eax &= u_supported;
+		entry->ebx = xstate_required_size(u_supported, false);
+		entry->ecx = entry->ebx;
+		entry->edx = 0;
+		break;
+	case 1:
+		supported = u_supported | s_supported;
+		entry->eax &= kvm_cpuid_D_1_eax_x86_features;
+		cpuid_mask(&entry->eax, CPUID_D_1_EAX);
+		entry->ebx = 0;
+		entry->edx = 0;
+		entry->ecx &= s_supported;
+		if (entry->eax & (F(XSAVES) | F(XSAVEC)))
+			entry->ebx = xstate_required_size(supported, true);
+
+		break;
+	default:
+		supported = (entry->ecx & 1) ? s_supported : u_supported;
+		if (!(supported & ((u64)1 << index))) {
+			entry->eax = 0;
+			entry->ebx = 0;
+			entry->ecx = 0;
+			entry->edx = 0;
+			return;
+		}
+		if (entry->ecx)
+			entry->ebx = 0;
+		entry->edx = 0;
+		break;
+	}
+}
+
 static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
 				  int *nent, int maxnent)
 {
@@ -428,7 +477,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
 	unsigned f_lm = 0;
 #endif
 	unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0;
-	unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
 	unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0;
 
 	/* cpuid 1.edx */
@@ -482,10 +530,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
 		F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
 		F(PMM) | F(PMM_EN);
 
-	/* cpuid 0xD.1.eax */
-	const u32 kvm_cpuid_D_1_eax_x86_features =
-		F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves;
-
 	/* all calls to cpuid_count() should be made on the same cpu */
 	get_cpu();
 
@@ -622,38 +666,22 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
 		break;
 	}
 	case 0xd: {
-		int idx, i;
-		u64 supported = kvm_supported_xcr0();
-
-		entry->eax &= supported;
-		entry->ebx = xstate_required_size(supported, false);
-		entry->ecx = entry->ebx;
-		entry->edx &= supported >> 32;
-		if (!supported)
-			break;
+		int i, idx;
 
-		for (idx = 1, i = 1; idx < 64; ++idx) {
-			u64 mask = ((u64)1 << idx);
+		do_cpuid_0xd_mask(&entry[0], 0);
+		for (i = 1, idx = 1; idx < 64; ++idx) {
 			if (*nent >= maxnent)
 				goto out;
-
 			do_host_cpuid(&entry[i], function, idx);
-			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);
-			} else {
-				if (entry[i].eax == 0 || !(supported & mask))
-					continue;
-				if (WARN_ON_ONCE(entry[i].ecx & 1))
-					continue;
-			}
-			entry[i].ecx = 0;
-			entry[i].edx = 0;
+			if (entry[i].eax == 0 && entry[i].ebx == 0 &&
+			    entry[i].ecx == 0 && entry[i].edx == 0)
+				continue;
+
+			do_cpuid_0xd_mask(&entry[i], idx);
+			if (entry[i].eax == 0 && entry[i].ebx == 0 &&
+			    entry[i].ecx == 0 && entry[i].edx == 0)
+				continue;
+
 			++*nent;
 			++i;
 		}
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e0368076a1ef..be967bf9a81d 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7193,6 +7193,11 @@ static bool svm_need_emulation_on_page_fault(struct kvm_vcpu *vcpu)
 	return false;
 }
 
+static u64 svm_supported_xss(void)
+{
+	return 0;
+}
+
 static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.cpu_has_kvm_support = has_svm,
 	.disabled_by_bios = is_disabled,
@@ -7329,6 +7334,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.nested_get_evmcs_version = NULL,
 
 	.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
+
+	.supported_xss = svm_supported_xss,
 };
 
 static int __init svm_init(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c6f6b05004d9..a84198cff397 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1651,6 +1651,11 @@ static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu,
 	return !(val & ~valid_bits);
 }
 
+static inline u64 vmx_supported_xss(void)
+{
+	return host_xss;
+}
+
 static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
 {
 	switch (msr->index) {
@@ -7799,6 +7804,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
 	.nested_enable_evmcs = NULL,
 	.nested_get_evmcs_version = NULL,
 	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
+	.supported_xss = vmx_supported_xss,
 };
 
 static void vmx_cleanup_l1d_flush(void)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 6594020c0691..fbffabad0370 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -293,6 +293,13 @@ 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)
+
+/*
+ * Right now, no XSS states are used on x86 platform,
+ * expand the macro for new features.
+ */
+#define KVM_SUPPORTED_XSS	(0)
+
 extern u64 host_xcr0;
 
 extern u64 kvm_supported_xcr0(void);
-- 
2.17.2