Re: [PATCH 1/2] KVM: TDX: Allow TDs to read MSR_IA32_PLATFORM_ID

Dave Hansen
2026-04-28T18:49:27Z

On 4/27/26 19:47, Binbin Wu wrote:
> Linux kernel reads MSR_IA32_PLATFORM_ID during init since commit
> d8630b67ca1e ("x86/cpu: Add platform ID to CPU info structure"). KVM
> already supports this MSR on read for normal VMs by returning 0.
> Without support for this MSR, TDs get unchecked MSR access errors.

NAK from me on this.

The platform ID is used for one thing and one thing only: microcode
updates. Those updates are solely the domain of the bare-metal OS.

The (guest) kernel code that's even trying to touch this MSR is buggy
and insane. We need to turn that code it off when
X86_FEATURE_HYPERVISOR==1. There's already a patch floating around to do
that.

Please don't add more smoke and mirrors.