On Wed, Mar 31, 2021, Dave Hansen wrote:
> On 3/31/21 2:53 PM, Sean Christopherson wrote:
> > 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.
>
> So, what should we do? In the #VE handler:
>
> switch (exit_reason) {
> case SOMETHING_WE_HANDLE:
> blah();
> break;
> ...
> default:
> pr_err("unhadled #VE, exit reason: %d\n", exit_reason);
> BUG_ON(1);
> }
>
> ?
>
> Is this the *ONLY* one of these, or are we going to have another twenty?
>
> If this is the only one, we might as well give a nice string error
> message. If there are twenty more, let's just dump the exit reason,
> BUG() and move on with our lives.
I've no objection to a nice message in the #VE handler. What I'm objecting to
is sanity checking the CPUID model provided by the TDX module. If we don't
trust the TDX module to honor the spec, then there are a huge pile of things
that are far higher priority than MONITOR/MWAIT.
