Re: [PATCH v8 06/30] KVM: selftests: Add helper functions to create TDX VMs

On 8/12/2025 4:13 AM, Sean Christopherson wrote: [...]

...

+void __tdx_mask_cpuid_features(struct kvm_cpuid_entry2 *entry) +{

• /*

• * Only entries with sub-leaf zero need to be masked, but some of these
  

• * leaves have other sub-leaves defined. Bail on any non-zero sub-leaf,
  

• * so they don't get unintentionally modified.
  

• */
  

• if (entry->index)

• return;
  

• switch (entry->function) {
• case 0x1:

• entry->ecx &= ~(CPUID_EXT_VMX | CPUID_EXT_SMX);
  

• entry->edx &= ~CPUID_PSE36;
  

vcpu_clear_cpuid_feature()

...

• break;
  

• case 0x7:

• entry->ebx &= ~(CPUID_7_0_EBX_TSC_ADJUST | CPUID_7_0_EBX_SGX);
  

• entry->ebx &= ~CPUID_7_0_EBX_INTEL_PT;
  

• entry->ecx &= ~CPUID_7_0_ECX_SGX_LC;
  

• break;
  

• case 0x40000001:

• entry->eax &= TDX_SUPPORTED_KVM_FEATURES;
  

• break;
  

• case 0x80000007:

• entry->edx |= CPUID_APM_INVTSC;
  

Quite obviously isn't "masking" anything".

Beside that, I guess this is handling fixed1 bit. But why only this bit is treated specially?