Re: [PATCH v3 0/4] KVM: TDX: Validate directly configurable CPUID bits
From: Xiaoyao Li
Date: Tue Sep 01 2026 - 05:58:30 EST
On 8/31/2026 1:01 PM, Binbin Wu wrote:
So if the approach in this series is taken, I think we still need such an opt-Yep. Can we think about what it would look like? Easiest would be a bit passed
in interface to tell the TDX module that the VMM is now filtering the CPUID
bits so that the TDX module knows that it's safe to report new host state
clobbering features.
in TDH_SYS_CONFIG. But then arch/x86 is saying how KVM will behave. Ok to me,
for the simplicity. Could come with a nice comment.
Can you just treat current KVM behavior of allowing userspace to enable any configurable bits as the bug of KVM and backport this series as Binbin suggested below? Instead of introducing more opt-in knobs.
The TDX module is initialized before KVM is loaded. I guess the upstream kernel
doesn't support out of tree KVM code, so we can assume if the kernel has the code to
opt-in the new host state clobbering features, KVM must have implemented the TDX
CPUID filtering and validation?
Also, do you think it's reasonable to backport this patch series to stable/LTS
kernels as an alternative?