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Message-ID: <d6bd0dc3-7309-473f-b763-47c6b534bb56@linux.intel.com>
Date: Mon, 8 Sep 2025 15:19:13 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sagi Shahar <sagis@...gle.com>
Cc: 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>,
Roger Wang <runanwang@...gle.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>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Subject: Re: [PATCH v10 07/21] KVM: selftests: Define structs to pass
parameters to TDX boot code
On 9/4/2025 2:54 PM, Sagi Shahar wrote:
> TDX registers are inaccesible to KVM. Therefore we need a different
inaccesible -> inaccessible
> mechanism to load boot parameters for TDX code. TDX boot code will read
> the registers values from memory and set the registers manually.
>
> This patch defines the data structures used to communicate between c
> code and the TDX assembly boot code which will be added in a later
> patch.
>
> Use kbuild.h to expose the offsets into the structs from c code to
> assembly code.
>
> Co-developed-by: Ackerley Tng<ackerleytng@...gle.com>
> Signed-off-by: Ackerley Tng<ackerleytng@...gle.com>
> Signed-off-by: Sagi Shahar<sagis@...gle.com>
One typo above and one nit comment below.
Otherwise,
Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>
> ---
> tools/testing/selftests/kvm/Makefile.kvm | 18 +++++
> .../selftests/kvm/include/x86/tdx/td_boot.h | 69 +++++++++++++++++++
> .../kvm/lib/x86/tdx/td_boot_offsets.c | 21 ++++++
> 3 files changed, 108 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/include/x86/tdx/td_boot.h
> create mode 100644 tools/testing/selftests/kvm/lib/x86/tdx/td_boot_offsets.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
> index 41b40c676d7f..3f93c093b046 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
> @@ -230,6 +232,10 @@ 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
> @@ -282,6 +288,7 @@ 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))
> @@ -308,6 +315,7 @@ $(SPLIT_TEST_GEN_OBJ): $(OUTPUT)/$(ARCH)/%.o: $(ARCH)/%.c
>
> EXTRA_CLEAN += $(GEN_HDRS) \
> $(LIBKVM_OBJS) \
> + $(LIBKVM_ASM_DEFS_OBJ) \
> $(SPLIT_TEST_GEN_OBJ) \
> $(TEST_DEP_FILES) \
> $(TEST_GEN_OBJ) \
> @@ -319,18 +327,28 @@ $(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.
> $(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
> $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
>
> +$(OUTPUT)/include/x86/tdx/td_boot_offsets.h: $(OUTPUT)/lib/x86/tdx/td_boot_offsets.s FORCE
> + $(call filechk,offsets,__TDX_BOOT_OFFSETS_H__)
> +
> +EXTRA_CLEAN += $(OUTPUT)/include/x86/tdx/td_boot_offsets.h
> +
> $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
> $(SPLIT_TEST_GEN_OBJ): $(GEN_HDRS)
> $(TEST_GEN_PROGS): $(LIBKVM_OBJS)
> $(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)
> $(TEST_GEN_OBJ): $(GEN_HDRS)
>
> +FORCE:
> +
> cscope: include_paths = $(LINUX_TOOL_INCLUDE) $(LINUX_HDR_PATH) include lib ..
> cscope:
> $(RM) cscope.*
> 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..8eda3ce10220
> --- /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 {
> + uint16_t limit;
> + uint32_t base;
> +};
> +
> +/*
> + * Allows each vCPU to be initialized with different eip and esp.
Nit:
Since guest_code is 64bit and the value is used when the vCPU is in 64bit mode,
eip -> rip?
> + */
> +struct td_per_vcpu_parameters {
> + uint32_t esp_gva;
> + uint64_t 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 {
> + uint32_t cr0;
> + uint32_t cr3;
> + uint32_t 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));
> +}
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