Re: [PATCH v19 105/130] KVM: TDX: handle KVM hypercall with TDG.VP.VMCALL

Chao Gao
2024-04-02T08:53:02Z

>+static int tdx_emulate_vmcall(struct kvm_vcpu *vcpu)
>+{
>+ unsigned long nr, a0, a1, a2, a3, ret;
>+

do you need to emulate xen/hyper-v hypercalls here?

Nothing tells userspace that xen/hyper-v hypercalls are not supported and
so userspace may expose related CPUID leafs to TD guests.

>+ /*
>+ * ABI for KVM tdvmcall argument:
>+ * In Guest-Hypervisor Communication Interface(GHCI) specification,
>+ * Non-zero leaf number (R10 != 0) is defined to indicate
>+ * vendor-specific. KVM uses this for KVM hypercall. NOTE: KVM
>+ * hypercall number starts from one. Zero isn't used for KVM hypercall
>+ * number.
>+ *
>+ * R10: KVM hypercall number
>+ * arguments: R11, R12, R13, R14.
>+ */
>+ nr = kvm_r10_read(vcpu);
>+ a0 = kvm_r11_read(vcpu);
>+ a1 = kvm_r12_read(vcpu);
>+ a2 = kvm_r13_read(vcpu);
>+ a3 = kvm_r14_read(vcpu);
>+
>+ ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, true, 0);
>+
>+ tdvmcall_set_return_code(vcpu, ret);
>+
>+ if (nr == KVM_HC_MAP_GPA_RANGE && !ret)
>+ return 0;

Can you add a comment to call out that KVM_HC_MAP_GPA_RANGE is redirected to
the userspace?

>+ return 1;
>+}