Re: [PATCH v6 43/60] i386/tdx: Only configure MSR_IA32_UCODE_REV in kvm_init_msrs() for TDs

Paolo Bonzini
2024-12-17T09:41:48Z

On 12/13/24 15:42, Ira Weiny wrote:
> On Tue, Nov 05, 2024 at 01:23:51AM -0500, Xiaoyao Li wrote:
>> For TDs, only MSR_IA32_UCODE_REV in kvm_init_msrs() can be configured
>> by VMM, while the features enumerated/controlled by other MSRs except
>> MSR_IA32_UCODE_REV in kvm_init_msrs() are not under control of VMM.
>
> I'm confused by this commit message. If these features are not under VMM
> control with TDX who controls them? I assume it is the TDX module. But where
> are the qemu hooks to talk to the module? Are they not needed in qemu at all?

The TDX module controls the values of the MSRs, and the values cannot be
affected by QEMU so there is nothing that QEMU needs to (or can) do.

> Also, why are the has_msr_* flags true for a TDX TD in the first place?

KVM only provides a system ioctl for this purpose, not a VM ioctl; so
there is currently no way to obtain the information for the VM.

Paolo