[PATCH v13 07/22] KVM: selftests: Introduce structures for TDX guest boot parameters
From: Lisa Wang
Date: Thu May 21 2026 - 19:19:37 EST
From: Sagi Shahar <sagis@xxxxxxxxxx>
Introduce `td_boot_parameters` and `td_per_vcpu_parameters`, and export
their offsets to assembly via the kbuild infrastructure.
TDX guest registers are private and must be initialized by guest-side
assembly. These structures allow the assembly code to retrieve boot
parameters and index into per-vCPU data based on the vCPU ID, while
keeping host and guest definitions synchronized.
Use kbuild.h to expose the offsets into the structs from c code to
assembly code.
Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
Co-developed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
Co-developed-by: Lisa Wang <wyihan@xxxxxxxxxx>
Signed-off-by: Lisa Wang <wyihan@xxxxxxxxxx>
---
tools/testing/selftests/kvm/.gitignore | 3 +-
tools/testing/selftests/kvm/Makefile.kvm | 29 ++++++++-
.../selftests/kvm/include/x86/tdx/td_boot.h | 69 ++++++++++++++++++++++
.../selftests/kvm/lib/x86/tdx/td_boot_offsets.c | 21 +++++++
4 files changed, 119 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 1d41a046a7bf..eef6055242b2 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -9,4 +9,5 @@
!config
!settings
!Makefile
-!Makefile.kvm
\ No newline at end of file
+!Makefile.kvm
+include/x86/**/*_offsets.h
\ No newline at end of file
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index e5769268936a..02fad7b35eac 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -19,6 +19,8 @@ LIBKVM += lib/userfaultfd_util.c
LIBKVM_STRING += lib/string_override.c
+LIBKVM_ASM_DEFS += lib/x86/tdx/td_boot_offsets.c
+
LIBKVM_x86 += lib/x86/apic.c
LIBKVM_x86 += lib/x86/handlers.S
LIBKVM_x86 += lib/x86/hyperv.c
@@ -260,6 +262,10 @@ OVERRIDE_TARGETS = 1
include ../lib.mk
include ../cgroup/lib/libcgroup.mk
+# Enable Kbuild tools.
+include $(top_srcdir)/scripts/Kbuild.include
+include $(top_srcdir)/scripts/Makefile.lib
+
INSTALL_HDR_PATH = $(top_srcdir)/usr
LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
LINUX_TOOL_INCLUDE = $(top_srcdir)/tools/include
@@ -272,15 +278,24 @@ CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
-fno-stack-protector -fno-PIE -fno-strict-aliasing \
-I$(LINUX_TOOL_INCLUDE) -I$(LINUX_TOOL_ARCH_INCLUDE) \
-I$(LINUX_HDR_PATH) -Iinclude -I$(<D) -Iinclude/$(ARCH) \
- -I ../rseq -I.. $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
+ -I ../rseq -I.. -I$(OUTPUT)/include/$(ARCH) $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
ifeq ($(ARCH),s390)
CFLAGS += -march=z10
endif
+
ifeq ($(ARCH),x86)
+
ifeq ($(shell echo "void foo(void) { }" | $(CC) -march=x86-64-v2 -x c - -c -o /dev/null 2>/dev/null; echo "$$?"),0)
CFLAGS += -march=x86-64-v2
endif
+
+KVM_GEN_HDRS := $(patsubst lib/x86/%.c, $(OUTPUT)/include/x86/%.h, $(filter lib/x86/%, $(LIBKVM_ASM_DEFS)))
+$(shell mkdir -p $(sort $(dir $(KVM_GEN_HDRS))))
+$(KVM_GEN_HDRS): GUARD = $(shell echo $(*F) | tr a-z A-Z | tr '.' '_')
+$(KVM_GEN_HDRS): $(OUTPUT)/include/x86/%.h: $(OUTPUT)/lib/x86/%.s FORCE
+ $(call filechk,offsets,__$(GUARD)_H__)
endif
+
ifeq ($(ARCH),arm64)
tools_dir := $(top_srcdir)/tools
arm64_tools_dir := $(tools_dir)/arch/arm64/tools/
@@ -313,6 +328,7 @@ LIBKVM_S := $(filter %.S,$(LIBKVM))
LIBKVM_C_OBJ := $(patsubst %.c, $(OUTPUT)/%.o, $(LIBKVM_C))
LIBKVM_S_OBJ := $(patsubst %.S, $(OUTPUT)/%.o, $(LIBKVM_S))
LIBKVM_STRING_OBJ := $(patsubst %.c, $(OUTPUT)/%.o, $(LIBKVM_STRING))
+LIBKVM_ASM_DEFS_OBJ += $(patsubst %.c, $(OUTPUT)/%.s, $(LIBKVM_ASM_DEFS))
LIBKVM_OBJS = $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ) $(LIBKVM_STRING_OBJ) $(LIBCGROUP_O)
SPLIT_TEST_GEN_PROGS := $(patsubst %, $(OUTPUT)/%, $(SPLIT_TESTS))
SPLIT_TEST_GEN_OBJ := $(patsubst %, $(OUTPUT)/$(ARCH)/%.o, $(SPLIT_TESTS))
@@ -338,7 +354,9 @@ $(SPLIT_TEST_GEN_OBJ): $(OUTPUT)/$(ARCH)/%.o: $(ARCH)/%.c
$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
EXTRA_CLEAN += $(GEN_HDRS) \
+ $(KVM_GEN_HDRS) \
$(LIBKVM_OBJS) \
+ $(LIBKVM_ASM_DEFS_OBJ) \
$(SPLIT_TEST_GEN_OBJ) \
$(TEST_DEP_FILES) \
$(TEST_GEN_OBJ) \
@@ -350,6 +368,9 @@ $(LIBKVM_C_OBJ): $(OUTPUT)/%.o: %.c $(GEN_HDRS)
$(LIBKVM_S_OBJ): $(OUTPUT)/%.o: %.S $(GEN_HDRS)
$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
+$(LIBKVM_ASM_DEFS_OBJ): $(OUTPUT)/%.s: %.c FORCE
+ $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -S $< -o $@
+
# Compile the string overrides as freestanding to prevent the compiler from
# generating self-referential code, e.g. without "freestanding" the compiler may
# "optimize" memcmp() by invoking memcmp(), thus causing infinite recursion.
@@ -358,11 +379,15 @@ $(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
$(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
$(SPLIT_TEST_GEN_OBJ): $(GEN_HDRS)
+$(LIBKVM_OBJS): $(KVM_GEN_HDRS)
$(TEST_GEN_PROGS): $(LIBKVM_OBJS)
$(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)
$(TEST_GEN_OBJ): $(GEN_HDRS)
-cscope: include_paths = $(LINUX_TOOL_INCLUDE) $(LINUX_HDR_PATH) include lib ..
+FORCE:
+
+cscope: include_paths = $(LINUX_TOOL_INCLUDE) $(LINUX_HDR_PATH) include lib .. \
+ $(wildcard $(sort $(dir $(KVM_GEN_HDRS))))
cscope:
$(RM) cscope.*
(find $(include_paths) -name '*.h' \
diff --git a/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h b/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h
new file mode 100644
index 000000000000..af4474dee387
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef SELFTEST_TDX_TD_BOOT_H
+#define SELFTEST_TDX_TD_BOOT_H
+
+#include <stdint.h>
+
+#include <linux/compiler.h>
+#include <linux/sizes.h>
+
+/*
+ * Layout for boot section (not to scale)
+ *
+ * GPA
+ * _________________________________ 0x1_0000_0000 (4GB)
+ * | Boot code trampoline |
+ * |___________________________|____ 0x0_ffff_fff0: Reset vector (16B below 4GB)
+ * | Boot code |
+ * |___________________________|____ td_boot will be copied here, so that the
+ * | | jmp to td_boot is exactly at the reset vector
+ * | Empty space |
+ * | |
+ * |───────────────────────────|
+ * | |
+ * | |
+ * | Boot parameters |
+ * | |
+ * | |
+ * |___________________________|____ 0x0_ffff_0000: TD_BOOT_PARAMETERS_GPA
+ */
+#define FOUR_GIGABYTES_GPA (SZ_4G)
+
+/*
+ * The exact memory layout for LGDT or LIDT instructions.
+ */
+struct __packed td_boot_parameters_dtr {
+ u16 limit;
+ u32 base;
+};
+
+/*
+ * Allows each vCPU to be initialized with different rip and esp.
+ */
+struct td_per_vcpu_parameters {
+ u32 esp_gva;
+ u64 guest_code;
+};
+
+/*
+ * Boot parameters for the TD.
+ *
+ * Unlike a regular VM, KVM cannot set registers such as esp, eip, etc
+ * before boot, so to run selftests, these registers' values have to be
+ * initialized by the TD.
+ *
+ * This struct is loaded in TD private memory at TD_BOOT_PARAMETERS_GPA.
+ *
+ * The TD boot code will read off parameters from this struct and set up the
+ * vCPU for executing selftests.
+ */
+struct td_boot_parameters {
+ u32 cr0;
+ u32 cr3;
+ u32 cr4;
+ struct td_boot_parameters_dtr gdtr;
+ struct td_boot_parameters_dtr idtr;
+ struct td_per_vcpu_parameters per_vcpu[];
+};
+
+#endif /* SELFTEST_TDX_TD_BOOT_H */
diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/td_boot_offsets.c b/tools/testing/selftests/kvm/lib/x86/tdx/td_boot_offsets.c
new file mode 100644
index 000000000000..7f76a3585b99
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86/tdx/td_boot_offsets.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+#define COMPILE_OFFSETS
+
+#include <linux/kbuild.h>
+
+#include "tdx/td_boot.h"
+
+static void __attribute__((used)) common(void)
+{
+ OFFSET(TD_BOOT_PARAMETERS_CR0, td_boot_parameters, cr0);
+ OFFSET(TD_BOOT_PARAMETERS_CR3, td_boot_parameters, cr3);
+ OFFSET(TD_BOOT_PARAMETERS_CR4, td_boot_parameters, cr4);
+ OFFSET(TD_BOOT_PARAMETERS_GDT, td_boot_parameters, gdtr);
+ OFFSET(TD_BOOT_PARAMETERS_IDT, td_boot_parameters, idtr);
+ OFFSET(TD_BOOT_PARAMETERS_PER_VCPU, td_boot_parameters, per_vcpu);
+ OFFSET(TD_PER_VCPU_PARAMETERS_ESP_GVA, td_per_vcpu_parameters, esp_gva);
+ OFFSET(TD_PER_VCPU_PARAMETERS_GUEST_CODE, td_per_vcpu_parameters,
+ guest_code);
+ DEFINE(SIZEOF_TD_PER_VCPU_PARAMETERS,
+ sizeof(struct td_per_vcpu_parameters));
+}
--
2.54.0.746.g67dd491aae-goog