[RFC PATCH v6 089/104] KVM: TDX: handle KVM hypercall with TDG.VP.VMCALL

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

The TDX Guest-Host communication interface (GHCI) specification defines
the ABI for the guest TD to issue hypercall.   It reserves vendor specific
arguments for VMM specific use.  Use it as KVM hypercall and handle it.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
 arch/x86/kvm/vmx/tdx.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 3c6cf08a2e3c..9c712f661a7c 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -918,8 +918,39 @@ static int tdx_handle_triple_fault(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+static int tdx_emulate_vmcall(struct kvm_vcpu *vcpu)
+{
+	unsigned long nr, a0, a1, a2, a3, ret;
+
+	/*
+	 * 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);
+
+	tdvmcall_set_return_code(vcpu, ret);
+
+	return 1;
+}
+
 static int handle_tdvmcall(struct kvm_vcpu *vcpu)
 {
+	if (tdvmcall_exit_type(vcpu))
+		return tdx_emulate_vmcall(vcpu);
+
 	switch (tdvmcall_leaf(vcpu)) {
 	default:
 		break;
-- 
2.25.1