KVM: x86: check for nEPT/nNPT in slow flush hypercalls

commit 464af6f upstream.

Checking is_guest_mode(vcpu) is incorrect, because translate_nested_gpa()
is only valid if an L2 guest is running *with nested EPT/NPT enabled*.
Instead use the same condition as translate_nested_gpa() itself.

Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <seanjc@google.com>
Fixes: aee7382 ("KVM: x86: Prepare kvm_hv_flush_tlb() to handle L2's GPAs", 2022-11-18)
Link: https://patch.msgid.link/20260503200905.106077-1-pbonzini@redhat.com/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: bonzini

arch/x86/kvm/hyperv.c

@@ -1987,7 +1987,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 	 * flush).  Translate the address here so the memory can be uniformly
 	 * read with kvm_read_guest().
 	 */
-	if (!hc->fast && is_guest_mode(vcpu)) {
+	if (!hc->fast && mmu_is_nested(vcpu)) {
 		hc->ingpa = translate_nested_gpa(vcpu, hc->ingpa, 0, NULL);
 		if (unlikely(hc->ingpa == INVALID_GPA))
 			return HV_STATUS_INVALID_HYPERCALL_INPUT;