KVM_RISCV_VCPU_MAX_HFENCE
struct kvm_riscv_hfence hfence_queue[KVM_RISCV_VCPU_MAX_HFENCE];
if (varch->hfence_head == KVM_RISCV_VCPU_MAX_HFENCE)
if (varch->hfence_tail == KVM_RISCV_VCPU_MAX_HFENCE)