KVM: x86/mmu: WARN if root_hpa is invalid when handling a page fault

WARN if root_hpa is invalid when handling a page fault.  The check on
root_hpa exists for historical reasons that no longer apply to the
current KVM code base.

Remove an equivalent debug-only warning in direct_page_fault(), whose
existence more or less confirms that root_hpa should always be valid
when handling a page fault.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -4172,8 +4172,6 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
 	kvm_pfn_t pfn;
 	int level, r;
 
-	MMU_WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root_hpa));
-
 	if (page_fault_handle_page_track(vcpu, error_code, gfn))
 		return RET_PF_EMULATE;
 
@@ -5463,7 +5461,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
 	int r, emulation_type = 0;
 	bool direct = vcpu->arch.mmu->direct_map;
 
-	if (!VALID_PAGE(vcpu->arch.mmu->root_hpa))
+	if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root_hpa)))
 		return RET_PF_RETRY;
 
 	/* With shadow page tables, fault_address contains a GVA or nGPA.  */