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

Binbin Wu
2025-02-27T01:19:25Z

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@intel.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
---
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