On Wed, Mar 31, 2021, Kuppuswamy Sathyanarayanan wrote:
> Changes since v3:
> * WARN user if SEAM does not disable MONITOR/MWAIT instruction.
Why bother? There are a whole pile of features that are dictated by the TDX
module spec. MONITOR/MWAIT is about as uninteresting as it gets, e.g. absolute
worst case scenario is the guest kernel crashes, whereas a lot of spec
violations
would compromise the security of the guest.
> + case EXIT_REASON_MONITOR_INSTRUCTION:
> + case EXIT_REASON_MWAIT_INSTRUCTION:
> + /*
> + * MWAIT/MONITOR features are disabled by TDX Module (SEAM)
> + * and also re-suppressed in kernel by clearing
> + * X86_FEATURE_MWAIT CPU feature flag in tdx_early_init(). So
> + * if TD guest still executes MWAIT/MONITOR instruction with
> + * above suppression, it needs user attention.
> + */
> + WARN(1, "TD Guest used unsupported MWAIT/MONITOR
> instruction\n");
Why not just WARN_ONCE and call it good?
> + break;
> default:
> pr_warn("Unexpected #VE: %d\n", ve->exit_reason);
> return -EFAULT;
> --
> 2.25.1
>
