KVM: arm64: Fast-track kvm_mpidr_to_vcpu() when mpidr_data is available

If our fancy little table is present when calling kvm_mpidr_to_vcpu(),
use it to recover the corresponding vcpu.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Tested-by: Joey Gouly <joey.gouly@arm.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230927090911.3355209-10-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: Marc Zyngier

arch/arm64/kvm/arm.c

@@ -2388,6 +2388,18 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr)
 	unsigned long i;
 
 	mpidr &= MPIDR_HWID_BITMASK;
+
+	if (kvm->arch.mpidr_data) {
+		u16 idx = kvm_mpidr_index(kvm->arch.mpidr_data, mpidr);
+
+		vcpu = kvm_get_vcpu(kvm,
+				    kvm->arch.mpidr_data->cmpidr_to_idx[idx]);
+		if (mpidr != kvm_vcpu_get_mpidr_aff(vcpu))
+			vcpu = NULL;
+
+		return vcpu;
+	}
+
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		if (mpidr == kvm_vcpu_get_mpidr_aff(vcpu))
 			return vcpu;