Re: [PATCH v15 15/23] KVM: selftests: Call KVM_TDX_INIT_VCPU when creating a new TDX vcpu

[Binbin Wu]

On 10/2/2026 3:37 AM, Lisa Wang wrote:
> From: Sagi Shahar <sagis@xxxxxxxxxx>
> 
> TDX VMs need to issue the KVM_TDX_INIT_VCPU ioctl for each vcpu after
> vcpu creation.
> 
> KVM_TDX_INIT_VCPU has a strict prerequisite for the CPUID state. To
> satisfy this requirement, call KVM_TDX_GET_CPUID and KVM_SET_CPUID2 to
> pull the CPUID configuration from the TDCS and commit it into KVM,
> allowing KVM_TDX_INIT_VCPU to succeed.
> 
> Additionally, unlike tdx_vm_ioctl(), tdx_vcpu_ioctl() doesn't check
> hw_error. KVM's vCPU-scoped TDX ioctl handlers don't propagate SEAMCALL
> errors into hw_error: the error is handled in the kernel and only an
> errno is returned. Checking the ioctl's return value and errno is
> therefore sufficient.
> 
> Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
> Signed-off-by: Lisa Wang <wyihan@xxxxxxxxxx>
> ---
>  .../selftests/kvm/include/x86/tdx/tdx_util.h       | 20 +++++++++
>  tools/testing/selftests/kvm/lib/x86/processor.c    | 48 ++++++++++++++++++----
>  2 files changed, 60 insertions(+), 8 deletions(-)
> 
> 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 e529c587aeae..f5b2f32f2118 100644
> --- a/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> +++ b/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> @@ -46,6 +46,26 @@ static inline bool is_tdx_vm(struct kvm_vm *vm)
>  		    (unsigned long long)hw_error);			\
>  })
>  
> +#define __tdx_vcpu_ioctl(vcpu, cmd, _flags, arg)			\
> +({									\
> +	union {								\
> +		struct kvm_tdx_cmd c;					\
> +		unsigned long raw;					\
> +	} tdx_cmd = { .c = {						\
> +		.id = (cmd),						\
> +		.flags = (u32)(_flags),					\
> +		.data = (u64)(arg),					\
> +	} };								\
> +									\
> +	__vcpu_ioctl(vcpu, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd.raw);	\
> +})
> +
> +#define tdx_vcpu_ioctl(vcpu, cmd, flags, arg)				\
> +({									\
> +	int ret = __tdx_vcpu_ioctl(vcpu, cmd, flags, arg);		\
> +	TEST_ASSERT(!ret, "%s failed, errno: %d (%s)",			\
> +		     #cmd, errno, strerror(errno));			\
> +})

tdx_vm_ioctl() prints ret, tdx_vcpu_ioctl() doesn't.
Better to be consistent.

>  void tdx_init_vm(struct kvm_vm *vm);
>  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);
> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index 4a753fb43007..4af9cbf3fabb 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -876,16 +876,48 @@ gva_t kvm_allocate_vcpu_stack(struct kvm_vm *vm)
>  		    "__vm_alloc() did not provide a page-aligned address");
>  	stack_gva -= 8;
>  
> +	return stack_gva;
> +}
> +
> +static void tdx_vcpu_init(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_cpuid2 *cpuid;
> +
> +	cpuid = allocate_kvm_cpuid2(MAX_NR_CPUID_ENTRIES);
> +	tdx_vcpu_ioctl(vcpu, KVM_TDX_GET_CPUID, 0, cpuid);
> +	vcpu_init_cpuid(vcpu, cpuid);
> +	free(cpuid);
> +	tdx_vcpu_ioctl(vcpu, KVM_TDX_INIT_VCPU, 0, NULL);
> +}

Should this function better to be in tdx_util.c, like other tdx specific helpers?

> +
> +struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, u32 vcpu_id)
> +{
> +	struct kvm_mp_state mp_state;
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_regs regs;
> +
>  	vcpu = __vm_vcpu_add(vm, vcpu_id);
> -	vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid());
> -	vcpu_init_sregs(vm, vcpu);
> -	vcpu_init_xcrs(vm, vcpu);
>  
> -	/* Setup guest general purpose registers */
> -	vcpu_regs_get(vcpu, &regs);
> -	regs.rflags = regs.rflags | 0x2;
> -	regs.rsp = kvm_allocate_vcpu_stack(vm);
> -	vcpu_regs_set(vcpu, &regs);
> +	/*
> +	 * Both kvm_get_supported_cpuid() (for legacy VMs) and KVM_TDX_GET_CPUID
> +	 * (for TDX VMs) return VM-scoped CPUID. e.g. the APIC ID isn't
> +	 * populated per vCPU. This is fine because KVM selftests don't
> +	 * currently test CPUID topology enumeration.
> +	 */
> +	if (is_tdx_vm(vm)) {
> +		tdx_vcpu_init(vm, vcpu);
> +	} else {
> +		vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid());
> +
> +		vcpu_init_sregs(vm, vcpu);
> +		vcpu_init_xcrs(vm, vcpu);
> +
> +		/* Setup guest general purpose registers */
> +		vcpu_regs_get(vcpu, &regs);
> +		regs.rflags = regs.rflags | 0x2;
> +		regs.rsp = kvm_allocate_vcpu_stack(vm);
> +		vcpu_regs_set(vcpu, &regs);
> +	}
>  
>  	/* Setup the MP state */
>  	mp_state.mp_state = 0;
>