On Mon, 2024-03-25 at 22:31 +0000, Huang, Kai wrote: > (sorry replying from outlook due to some issue to my linux box environment) > > It booted because Qemu does sane thing, i.e., it always passes the correct CPUIDs in > KVM_SET_CPUID2. > > Per-Sean's comments, KVM should guarantee the consistency between CPUIDs done in TDH.MNG.INIT and > KVM_SET_CPUID2, otherwise if Qemu passes in-consistent CPUIDs KVM can easily fail to work with TD. > > To guarantee the consistency, KVM could do two options as we discussed: > > 1) reject KVM_SET_CPUID2 completely. > 2) Still allow KVM_SET_CPUID2 but manually check the CPUID consistency between the one done in > TDH.MNG.INIT and the one passed in KVM_SET_CPUID2. > > 1) can obviously guarantee consistency. But KVM maintains CPUIDs in 'vcpu', so to make the > existing KVM code continue to work, we need to manually set 'vcpu->cpuid' to the one that is done > in TDH.MNG.INIT. > > 2) you need to check the consistency and reject KVM_SET_CPUID2 if in-consistency found. But other > than that, KVM doesn't need to anything more because if we allow KVM_SET_CPUID2, the 'vcpu' will > have its own CPUIDs populated anyway. Ah, thanks for explaining. So 1 is not that simple, it is a maybe slightly smaller separate solution. Now I see why the discussion was to just do the consistency checking up front.
