Re: [RFC PATCH v2 02/11] KVM: x86: Advertise CPUID.7.2.EDX and RRSBA_CTRL support

[Chao Gao]

On Tue, May 16, 2023 at 10:22:22AM +0800, Xiaoyao Li wrote:
>> > I think we need to fix this bug at first.
>> 
>> I have no idea how to fix the "bug" without intercepting the MSR. The
>> performance penalty makes me think intercepting the MSR is not a viable
>> solution.
>
>I thought correctness always takes higher priority over performance.

It is generally true. however, there are situations where we should make
trade-offs between correctness and other factors (like performance):

E.g., instructions without control bits, to be 100% compliant with CPU
spec, in theory, VMMs can trap/decode every instruction and inject #UD
if a guest tries to use some instructions it shouldn't.