Re: [PATCH] x86/hvm: Include interruptibility state in hvm_hw_cpu

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Thu, Mar 17, 2022 at 11:06 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 17.03.2022 15:43, Tamas K Lengyel wrote:
> > On Thu, Mar 17, 2022 at 9:56 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> >> On 10.03.2022 19:44, Tamas K Lengyel wrote:
> >>> @@ -1155,6 +1154,8 @@ static int cf_check hvm_load_cpu_ctxt(struct domain 
> >>> *d, hvm_domain_context_t *h)
> >>>      v->arch.dr6   = ctxt.dr6;
> >>>      v->arch.dr7   = ctxt.dr7;
> >>>
> >>> +    hvm_set_interrupt_shadow(v, ctxt.interruptibility_info);
> >>
> >> Setting reserved bits as well as certain combinations of bits will
> >> cause VM entry to fail. I think it would be nice to report this as
> >> an error here rather than waiting for the VM entry failure.
> >
> > Not sure if this would be the right spot to do that since that's all
> > VMX specific and this is the common hvm code.
>
> Well, it would be the VMX hook to do the checking, with an error
> propagated back here.

I'm actually against it because the overhead of that error-checking
during vm forking would be significant with really no benefit. We are
copying the state from the parent where it was running fine before, so
doing that sanity checking thousands of times per second when we
already know its fine is bad.

Tamas