[PATCH v2 11/20] KVM: TDX: Handle TDG.VP.VMCALL<GetTdVmCallInfo> hypercall

[Binbin Wu]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Implement TDG.VP.VMCALL<GetTdVmCallInfo> hypercall.  If the input value is
zero, return success code and zero in output registers.

TDG.VP.VMCALL<GetTdVmCallInfo> hypercall is a subleaf of TDG.VP.VMCALL to
enumerate which TDG.VP.VMCALL sub leaves are supported.  This hypercall is
for future enhancement of the Guest-Host-Communication Interface (GHCI)
specification.  The GHCI version of 344426-001US defines it to require
input R12 to be zero and to return zero in output registers, R11, R12, R13,
and R14 so that guest TD enumerates no enhancement.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Signed-off-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
---
TDX "the rest" v2:
- Use vp_enter_args directly instead of helpers.
- Skip setting return code as TDVMCALL_STATUS_SUCCESS.
- Skip setting tdx->vp_enter_args.r12 to 0 because it already is 0.

TDX "the rest" v1:
- Use TDVMCALL_STATUS prefix for TDX call status codes (Binbin)

v19:
- rename TDG_VP_VMCALL_GET_TD_VM_CALL_INFO => TDVMCALL_GET_TD_VM_CALL_INFO
---
 arch/x86/include/asm/shared/tdx.h |  1 +
 arch/x86/kvm/vmx/tdx.c            | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index f23657350d28..606d93a1cbac 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -67,6 +67,7 @@
 #define TD_CTLS_LOCK			BIT_ULL(TD_CTLS_LOCK_BIT)
 
 /* TDX hypercall Leaf IDs */
+#define TDVMCALL_GET_TD_VM_CALL_INFO	0x10000
 #define TDVMCALL_MAP_GPA		0x10001
 #define TDVMCALL_GET_QUOTE		0x10002
 #define TDVMCALL_REPORT_FATAL_ERROR	0x10003
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 76764bf5ba29..dbc9fffcbc26 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1422,6 +1422,20 @@ static int tdx_emulate_mmio(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int tdx_get_td_vm_call_info(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_tdx *tdx = to_tdx(vcpu);
+
+	if (tdx->vp_enter_args.r12)
+		tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND);
+	else {
+		tdx->vp_enter_args.r11 = 0;
+		tdx->vp_enter_args.r13 = 0;
+		tdx->vp_enter_args.r14 = 0;
+	}
+	return 1;
+}
+
 static int handle_tdvmcall(struct kvm_vcpu *vcpu)
 {
 	switch (tdvmcall_leaf(vcpu)) {
@@ -1429,6 +1443,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
 		return tdx_map_gpa(vcpu);
 	case TDVMCALL_REPORT_FATAL_ERROR:
 		return tdx_report_fatal_error(vcpu);
+	case TDVMCALL_GET_TD_VM_CALL_INFO:
+		return tdx_get_td_vm_call_info(vcpu);
 	default:
 		break;
 	}
-- 
2.46.0