Re: [RFC PATCH v5 100/104] KVM: TDX: Silently discard SMI request

[Paolo Bonzini]

On 3/4/22 20:49, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> TDX doesn't support system-management mode (SMM) and system-management
> interrupt (SMI) in guest TDs.  Because guest state (vcpu state, memory
> state) is protected, it must go through the TDX module APIs to change guest
> state, injecting SMI and changing vcpu mode into SMM.  The TDX module
> doesn't provide a way for VMM to inject SMI into guest TD and a way for VMM
> to switch guest vcpu mode into SMM.
>
> We have two options in KVM when handling SMM or SMI in the guest TD or the
> device model (e.g. QEMU): 1) silently ignore the request or 2) return a
> meaningful error.
>
> For simplicity, we implemented the option 1).

Please also:

1) return zero from vmx_has_emulated_msr(MSR_IA32_SMBASE) for TDX 
virtual machines.

2) do a check for static_call(kvm_x86_has_emulated_msr)(kvm, 
MSR_IA32_SMBASE) in kvm_vcpu_ioctl_smi and __apic_accept_irq.

3) WARN_ON_ONCE in tdx_smi_allowed and tdx_enable_smi_window.

Paolo