[RFC 09/33] KVM: x86: hyper-v: Introduce per-VTL vcpu helpers

[Nicolas Saenz Julienne <nsaenz@amazon.com>]

Introduce two helper functions. The first one queries a vCPU's VTL
level, the second one, given a struct kvm_vcpu and VTL pair, returns the
corresponding 'sibling' struct kvm_vcpu at the right VTL.

We keep track of each VTL's state by having a distinct struct kvm_vpcu
for each level. VTL-vCPUs that belong to the same guest CPU share the
same physical APIC id, but belong to different APIC groups where the
apic group represents the vCPU's VTL.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
---
 arch/x86/kvm/hyperv.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 2bfed69ba0db..5433107e7cc8 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -23,6 +23,7 @@
 
 #include <linux/kvm_host.h>
 #include "x86.h"
+#include "lapic.h"
 
 /* "Hv#1" signature */
 #define HYPERV_CPUID_SIGNATURE_EAX 0x31237648
@@ -83,6 +84,23 @@ static inline struct kvm_hv_syndbg *to_hv_syndbg(struct kvm_vcpu *vcpu)
 	return &vcpu->kvm->arch.hyperv.hv_syndbg;
 }
 
+static inline struct kvm_vcpu *kvm_hv_get_vtl_vcpu(struct kvm_vcpu *vcpu, int vtl)
+{
+	struct kvm *kvm = vcpu->kvm;
+	u32 target_id = kvm_apic_id(vcpu);
+
+	kvm_apic_id_set_group(kvm, vtl, &target_id);
+	if (vcpu->vcpu_id == target_id)
+		return vcpu;
+
+	return kvm_get_vcpu_by_id(kvm, target_id);
+}
+
+static inline u8 kvm_hv_get_active_vtl(struct kvm_vcpu *vcpu)
+{
+	return kvm_apic_group(vcpu);
+}
+
 static inline u32 kvm_hv_get_vpindex(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
-- 
2.40.1