Re: [PATCH v14 11/22] KVM: selftests: Set up TDX boot parameters region

[Binbin Wu]

On 7/23/2026 7:13 AM, Lisa Wang wrote:
> From: Sagi Shahar <sagis@xxxxxxxxxx>
> 
> Allocate memory for TDX boot parameters and define the utility functions
> necessary to fill this memory with the boot parameters.

The code change looks good to me.

But I think it's better to describe how the parameters are initialized based
on the HVA when VM_MEM_SRC_SHMEM is used alongside KVM_MEM_GUEST_MEMFD.
Same for the patch 10.

> 
> Co-developed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
> Signed-off-by: Lisa Wang <wyihan@xxxxxxxxxx>
> ---
>  .../selftests/kvm/include/x86/tdx/tdx_util.h       |  2 +
>  tools/testing/selftests/kvm/lib/x86/processor.c    |  2 +
>  tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c | 51 ++++++++++++++++++++++
>  3 files changed, 55 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h b/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> index 642ffa010da3..f5003cbaa106 100644
> --- a/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> +++ b/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> @@ -46,5 +46,7 @@ static inline bool is_tdx_vm(struct kvm_vm *vm)
>  
>  void tdx_init_vm(struct kvm_vm *vm, u64 attributes);
>  void tdx_vm_setup_boot_code_region(struct kvm_vm *vm);
> +void tdx_vm_setup_boot_parameters_region(struct kvm_vm *vm, u32 nr_runnable_vcpus);
> +void tdx_vm_load_common_boot_parameters(struct kvm_vm *vm);
>  
>  #endif /* SELFTESTS_TDX_TDX_UTIL_H */
> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index f93953777ca1..748c6041f8bf 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -794,6 +794,8 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm, unsigned int nr_vcpus)
>  	if (is_tdx_vm(vm)) {
>  		tdx_init_vm(vm, 0);
>  		tdx_vm_setup_boot_code_region(vm);
> +		tdx_vm_setup_boot_parameters_region(vm, nr_vcpus);
> +		tdx_vm_load_common_boot_parameters(vm);
>  	}
>  
>  	r = __vm_ioctl(vm, KVM_GET_TSC_KHZ, NULL);
> diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> index d64d153d19e2..2ce8c297f7ed 100644
> --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> @@ -6,6 +6,7 @@
>  
>  /* Arbitrarily selected to avoid overlaps with anything else */
>  #define TD_BOOT_CODE_SLOT	20
> +#define TD_BOOT_PARAMETERS_SLOT	21
>  
>  #define X86_RESET_VECTOR	0xfffffff0ul
>  #define X86_RESET_VECTOR_SIZE	16
> @@ -49,6 +50,56 @@ void tdx_vm_setup_boot_code_region(struct kvm_vm *vm)
>  	hva[2] = 0xcc;
>  }
>  
> +void tdx_vm_setup_boot_parameters_region(struct kvm_vm *vm, u32 nr_runnable_vcpus)
> +{
> +	size_t boot_params_size =
> +		sizeof(struct td_boot_parameters) +
> +		nr_runnable_vcpus * sizeof(struct td_per_vcpu_parameters);
> +	int npages = DIV_ROUND_UP(boot_params_size, PAGE_SIZE);
> +	const u64 gmem_flags = 0;
> +	gpa_t gpa;
> +
> +	vm_mem_add(vm, VM_MEM_SRC_SHMEM, TD_BOOT_PARAMETERS_GPA,
> +		   TD_BOOT_PARAMETERS_SLOT, npages,
> +		   KVM_MEM_GUEST_MEMFD, -1, 0, gmem_flags);
> +	gpa = vm_phy_pages_alloc(vm, npages, TD_BOOT_PARAMETERS_GPA, TD_BOOT_PARAMETERS_SLOT);
> +	TEST_ASSERT(gpa == TD_BOOT_PARAMETERS_GPA, "Failed vm_phy_pages_alloc\n");
> +
> +	virt_map(vm, TD_BOOT_PARAMETERS_GPA, TD_BOOT_PARAMETERS_GPA, npages);
> +}
> +
> +void tdx_vm_load_common_boot_parameters(struct kvm_vm *vm)
> +{
> +	struct td_boot_parameters *params =
> +		addr_gpa2hva(vm, TD_BOOT_PARAMETERS_GPA);
> +	u32 cr4;
> +
> +	cr4 = kvm_get_default_cr4(vm->mmu.pgtable_levels);
> +
> +	/* TDX spec 11.6.2: CR4 bit MCE is fixed to 1 */
> +	cr4 |= X86_CR4_MCE;
> +
> +	/* TDX spec 11.6.2: CR4 bit VMXE and SMXE are fixed to 0 */
> +	cr4 &= ~(X86_CR4_VMXE | X86_CR4_SMXE);
> +
> +	/* Set parameters! */
> +	params->cr0 = kvm_get_default_cr0();
> +	TEST_ASSERT(vm->mmu.pgd < (1ULL << 32),
> +		    "PGD must be within 32-bit address space for 32-bit boot code");
> +	params->cr3 = vm->mmu.pgd;
> +	params->cr4 = cr4;
> +	params->idtr.base = vm->arch.idt;
> +	params->idtr.limit = kvm_get_default_idt_limit();
> +	params->gdtr.base = vm->arch.gdt;
> +	params->gdtr.limit = kvm_get_default_gdt_limit();
> +
> +	TEST_ASSERT(params->cr0 != 0, "cr0 should not be 0");
> +	TEST_ASSERT(params->cr3 != 0, "cr3 should not be 0");
> +	TEST_ASSERT(params->cr4 != 0, "cr4 should not be 0");
> +	TEST_ASSERT(params->gdtr.base != 0, "gdt base address should not be 0");
> +	TEST_ASSERT(params->idtr.base != 0, "idt base address should not be 0");
> +}
> +
>  static struct kvm_tdx_capabilities *tdx_read_capabilities(struct kvm_vm *vm)
>  {
>  	static struct kvm_tdx_capabilities *tdx_cap;
>