On 18/08/2025 21:49, Edgecombe, Rick P wrote: > Attn: Binbin, Xiaoyao > > On Mon, 2025-08-18 at 07:05 -0700, Sean Christopherson wrote: >> NAK. >> >> Fix the guest, or wherever else in the pile there are issues. KVM is NOT carrying >> hack-a-fixes to workaround buggy software/firmware. Been there, done that. > > Yes, I would have thought we should have at least had a TDX module change option > for this. That would not help with existing TDX Modules, and would possibly require a guest opt-in, which would not help with existing guests. Hence, to start with disabling the feature first, and look for another solution second. In the MWAIT case, Sean has rejected supporting MSR_PKG_CST_CONFIG_CONTROL even for VMX, because it is an optional MSR, so altering intel_idle is being proposed. > > But side topic. We have an existing arch TODO around creating some guidelines > around how CPUID bit configuration should evolve. > > A new directly configurable CPUID bit that affects host state is an obvious no- > no. But how about a directly configurable bit that can't hurt the host, but > requires host changes to virtualize in an x86 arch compliant way? (not quite > like this MWAIT case) It is still "new stuff that breaks old stuff" which is generally "just don't do that".
