[PATCH v3 06/25] KVM: x86: hyper-v: Cache HYPERV_CPUID_NESTED_FEATURES CPUID leaf

[Vitaly Kuznetsov]

KVM has to check guest visible HYPERV_CPUID_NESTED_FEATURES.EBX CPUID
leaf to know with Enlightened VMCS definition to use (original or 2022
update). Cache the leaf along with other Hyper-V CPUID feature leaves
to make the check quick.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h | 2 ++
 arch/x86/kvm/hyperv.c           | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index de5a149d0971..077ec9cf3169 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -616,6 +616,8 @@ struct kvm_vcpu_hv {
 		u32 enlightenments_eax; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EAX */
 		u32 enlightenments_ebx; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EBX */
 		u32 syndbg_cap_eax; /* HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX */
+		u32 nested_eax; /* HYPERV_CPUID_NESTED_FEATURES.EAX */
+		u32 nested_ebx; /* HYPERV_CPUID_NESTED_FEATURES.EBX */
 	} cpuid_cache;
 };
 
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index e08189211d9a..b666902da4d9 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2030,6 +2030,15 @@ void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu)
 		hv_vcpu->cpuid_cache.syndbg_cap_eax = entry->eax;
 	else
 		hv_vcpu->cpuid_cache.syndbg_cap_eax = 0;
+
+	entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_NESTED_FEATURES, 0);
+	if (entry) {
+		hv_vcpu->cpuid_cache.nested_eax = entry->eax;
+		hv_vcpu->cpuid_cache.nested_ebx = entry->ebx;
+	} else {
+		hv_vcpu->cpuid_cache.nested_eax = 0;
+		hv_vcpu->cpuid_cache.nested_ebx = 0;
+	}
 }
 
 int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce)
-- 
2.35.3