Add utility function to issue MMIO TDCALL from TDX guests.

Signed-off-by: Sagi Shahar <sagis@google.com>
---
 tools/testing/selftests/kvm/Makefile.kvm      |  1 +
 .../selftests/kvm/include/x86/tdx/tdx.h       | 14 +++++++++++
 tools/testing/selftests/kvm/lib/x86/tdx/tdx.c | 23 +++++++++++++++++++
 3 files changed, 38 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/include/x86/tdx/tdx.h
 create mode 100644 tools/testing/selftests/kvm/lib/x86/tdx/tdx.c

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 2d4fd68984a0..1a73e08c8437 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -35,6 +35,7 @@ LIBKVM_x86 += lib/x86/vmx.c
 LIBKVM_x86 += lib/x86/tdx/tdx_util.c
 LIBKVM_x86 += lib/x86/tdx/td_boot.S
 LIBKVM_x86 += lib/x86/tdx/tdcall.S
+LIBKVM_x86 += lib/x86/tdx/tdx.c
 
 LIBKVM_arm64 += lib/arm64/gic.c
 LIBKVM_arm64 += lib/arm64/gic_v3.c
diff --git a/tools/testing/selftests/kvm/include/x86/tdx/tdx.h b/tools/testing/selftests/kvm/include/x86/tdx/tdx.h
new file mode 100644
index 000000000000..22b096402998
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/x86/tdx/tdx.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef SELFTESTS_TDX_TDX_H
+#define SELFTESTS_TDX_TDX_H
+
+#include <stdint.h>
+
+/* MMIO direction */
+#define MMIO_READ	0
+#define MMIO_WRITE	1
+
+uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
+					     uint64_t data_in);
+
+#endif // SELFTESTS_TDX_TDX_H
diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
new file mode 100644
index 000000000000..f9c1acd5b30c
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "tdx/tdcall.h"
+#include "tdx/tdx.h"
+
+#define TDG_VP_VMCALL 0
+
+#define TDG_VP_VMCALL_VE_REQUEST_MMIO	48
+
+uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
+					     uint64_t data_in)
+{
+	struct tdx_tdcall_args args = {
+		.r10 = TDG_VP_VMCALL,
+		.r11 = TDG_VP_VMCALL_VE_REQUEST_MMIO,
+		.r12 = size,
+		.r13 = MMIO_WRITE,
+		.r14 = address,
+		.r15 = data_in,
+	};
+
+	return __tdx_tdcall(&args, 0);
+}
-- 
2.51.0.338.gd7d06c2dae-goog