Re: [PATCH v12 17/23] KVM: selftests: Call KVM_TDX_INIT_VCPU when creating a new TDX vcpu

[Binbin Wu]

On 10/29/2025 5:20 AM, Sagi Shahar wrote:

TDX VMs need to issue the KVM_TDX_INIT_VCPU ioctl for each vcpu after
vcpu creation.

Since the cpuids for TD are managed by the TDX module, read the values
virtualized for the TD using KVM_TDX_GET_CPUID and set them in kvm using
KVM_SET_CPUID2 so that kvm has an accurate view of the VM cpuid values.

Signed-off-by: Sagi Shahar <sa...@google.com>
---
  .../testing/selftests/kvm/lib/x86/processor.c | 35 ++++++++++++++-----
  1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c 
b/tools/testing/selftests/kvm/lib/x86/processor.c
index 990f2769c5d8..036875fe140f 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -722,6 +722,19 @@ vm_vaddr_t kvm_allocate_vcpu_stack(struct kvm_vm *vm)
        return stack_vaddr;
  }

+static void vm_tdx_vcpu_add(struct kvm_vm *vm, struct kvm_vcpu *vcpu)

+{
+       struct kvm_cpuid2 *cpuid;
+
+       cpuid = allocate_kvm_cpuid2(MAX_NR_CPUID_ENTRIES);
+       vm_tdx_vcpu_ioctl(vcpu, KVM_TDX_GET_CPUID, 0, cpuid);
+       vcpu_init_cpuid(vcpu, cpuid);
+       free(cpuid);
+       vm_tdx_vcpu_ioctl(vcpu, KVM_TDX_INIT_VCPU, 0, NULL);
+
+       vm_tdx_load_vcpu_boot_parameters(vm, vcpu);
+}
+
  struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
  {
        struct kvm_mp_state mp_state;
@@ -729,15 +742,21 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, 
uint32_t vcpu_id)
        struct kvm_vcpu *vcpu;

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);
+       if (is_tdx_vm(vm)) {
+               vm_tdx_vcpu_add(vm, vcpu);

Nit:
Since vcpu is added by  __vm_vcpu_add() above, using 'init' instead of 'add' in
the function name makes it more clear.

+       } 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;