[RFC PATCH v6 12/36] KVM: x86: hyper-v: Cache HYPERV_CPUID_NESTED_FEATURES CPUID leaf

Sean Christopherson
2022-08-24T03:04:06Z

KVM has to check guest visible HYPERV_CPUID_NESTED_FEATURES.EBX CPUID
leaf to know which 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.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/hyperv.c | 6 ++++++
2 files changed, 8 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2209724b765e..fa399329c9f8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -615,6 +615,8 @@ 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 bf4729e8cc80..a7478b61088b 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2018,6 +2018,12 @@ void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled)
entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES);
if (entry)
hv_vcpu->cpuid_cache.syndbg_cap_eax = entry->eax;
+
+ entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_NESTED_FEATURES);
+ if (entry) {
+ hv_vcpu->cpuid_cache.nested_eax = entry->eax;
+ hv_vcpu->cpuid_cache.nested_ebx = entry->ebx;
+ }
}

int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce)
--
2.37.1.595.g718a3a8f04-goog