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Message-ID: <20250821042915.3712925-10-sagis@google.com>
Date: Wed, 20 Aug 2025 21:29:02 -0700
From: Sagi Shahar <sagis@...gle.com>
To: linux-kselftest@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
Shuah Khan <shuah@...nel.org>, Sean Christopherson <seanjc@...gle.com>,
Ackerley Tng <ackerleytng@...gle.com>, Ryan Afranji <afranji@...gle.com>,
Andrew Jones <ajones@...tanamicro.com>, Isaku Yamahata <isaku.yamahata@...el.com>,
Erdem Aktas <erdemaktas@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>,
Sagi Shahar <sagis@...gle.com>, Roger Wang <runanwang@...gle.com>,
Binbin Wu <binbin.wu@...ux.intel.com>, Oliver Upton <oliver.upton@...ux.dev>,
"Pratik R. Sampat" <pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>,
Ira Weiny <ira.weiny@...el.com>, Chao Gao <chao.gao@...el.com>,
Chenyi Qiang <chenyi.qiang@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v9 09/19] KVM: selftests: Add TDX boot code
From: Erdem Aktas <erdemaktas@...gle.com>
Add code to boot a TDX test VM. Since TDX registers are inaccesible to
KVM, the boot code loads the relevant values from memory into the
registers before jumping to the guest code.
Signed-off-by: Erdem Aktas <erdemaktas@...gle.com>
Co-developed-by: Ackerley Tng <ackerleytng@...gle.com>
Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
Co-developed-by: Sagi Shahar <sagis@...gle.com>
Signed-off-by: Sagi Shahar <sagis@...gle.com>
---
tools/testing/selftests/kvm/Makefile.kvm | 3 +
.../selftests/kvm/include/x86/tdx/td_boot.h | 5 ++
.../kvm/include/x86/tdx/td_boot_asm.h | 16 +++++
.../selftests/kvm/lib/x86/tdx/td_boot.S | 60 +++++++++++++++++++
4 files changed, 84 insertions(+)
create mode 100644 tools/testing/selftests/kvm/include/x86/tdx/td_boot_asm.h
create mode 100644 tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index f4686445c197..03754ce2e983 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -31,6 +31,7 @@ LIBKVM_x86 += lib/x86/sev.c
LIBKVM_x86 += lib/x86/svm.c
LIBKVM_x86 += lib/x86/ucall.c
LIBKVM_x86 += lib/x86/vmx.c
+LIBKVM_x86 += lib/x86/tdx/td_boot.S
LIBKVM_arm64 += lib/arm64/gic.c
LIBKVM_arm64 += lib/arm64/gic_v3.c
@@ -335,6 +336,8 @@ $(LIBKVM_ASM_DEFS_OBJ): $(OUTPUT)/%.s: %.c FORCE
$(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
+$(OUTPUT)/lib/x86/tdx/td_boot.o: $(OUTPUT)/include/x86/tdx/td_boot_offsets.h
+
$(OUTPUT)/include/x86/tdx/td_boot_offsets.h: $(OUTPUT)/lib/x86/tdx/td_boot_offsets.s FORCE
$(call filechk,offsets,__TDX_BOOT_OFFSETS_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
index 5cce671586e9..65ccc65efaeb 100644
--- a/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h
+++ b/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h
@@ -73,4 +73,9 @@ struct td_boot_parameters {
struct td_per_vcpu_parameters per_vcpu[];
};
+void td_boot(void);
+void td_boot_code_end(void);
+
+#define TD_BOOT_CODE_SIZE (td_boot_code_end - td_boot)
+
#endif /* SELFTEST_TDX_TD_BOOT_H */
diff --git a/tools/testing/selftests/kvm/include/x86/tdx/td_boot_asm.h b/tools/testing/selftests/kvm/include/x86/tdx/td_boot_asm.h
new file mode 100644
index 000000000000..10b4b527595c
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/x86/tdx/td_boot_asm.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef SELFTEST_TDX_TD_BOOT_ASM_H
+#define SELFTEST_TDX_TD_BOOT_ASM_H
+
+/*
+ * GPA where TD boot parameters will be loaded.
+ *
+ * TD_BOOT_PARAMETERS_GPA is arbitrarily chosen to
+ *
+ * + be within the 4GB address space
+ * + provide enough contiguous memory for the struct td_boot_parameters such
+ * that there is one struct td_per_vcpu_parameters for KVM_MAX_VCPUS
+ */
+#define TD_BOOT_PARAMETERS_GPA 0xffff0000
+
+#endif // SELFTEST_TDX_TD_BOOT_ASM_H
diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S b/tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S
new file mode 100644
index 000000000000..7aa33caa9a78
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include "tdx/td_boot_asm.h"
+#include "tdx/td_boot_offsets.h"
+#include "processor_asm.h"
+
+.code32
+
+.globl td_boot
+td_boot:
+ /* In this procedure, edi is used as a temporary register. */
+ cli
+
+ /* Paging is off. */
+
+ movl $TD_BOOT_PARAMETERS_GPA, %ebx
+
+ /*
+ * Find the address of struct td_per_vcpu_parameters for this
+ * vCPU based on esi (TDX spec: initialized with vCPU id). Put
+ * struct address into register for indirect addressing.
+ */
+ movl $SIZEOF_TD_PER_VCPU_PARAMETERS, %eax
+ mul %esi
+ leal TD_BOOT_PARAMETERS_PER_VCPU(%ebx), %edi
+ addl %edi, %eax
+
+ /* Setup stack. */
+ movl TD_PER_VCPU_PARAMETERS_ESP_GVA(%eax), %esp
+
+ /* Setup GDT. */
+ leal TD_BOOT_PARAMETERS_GDT(%ebx), %edi
+ lgdt (%edi)
+
+ /* Setup IDT. */
+ leal TD_BOOT_PARAMETERS_IDT(%ebx), %edi
+ lidt (%edi)
+
+ /*
+ * Set up control registers (There are no instructions to mov from
+ * memory to control registers, hence use edi as a scratch register).
+ */
+ movl TD_BOOT_PARAMETERS_CR4(%ebx), %edi
+ movl %edi, %cr4
+ movl TD_BOOT_PARAMETERS_CR3(%ebx), %edi
+ movl %edi, %cr3
+ movl TD_BOOT_PARAMETERS_CR0(%ebx), %edi
+ movl %edi, %cr0
+
+ /* Switching to 64bit mode after ljmp and then jump to guest code */
+ ljmp $(KERNEL_CS),$1f
+1:
+ jmp *TD_PER_VCPU_PARAMETERS_GUEST_CODE(%eax)
+
+/* Leave marker so size of td_boot code can be computed. */
+.globl td_boot_code_end
+td_boot_code_end:
+
+/* Disable executable stack. */
+.section .note.GNU-stack,"",%progbits
--
2.51.0.rc1.193.gad69d77794-goog
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