Re: [RFC PATCH V2 16/18] x86/sev: Initialize #HV doorbell and handle interrupt requests

[Kalra, Ashish]

On 11/22/2022 7:46 AM, Tianyu Lan wrote:
> On 11/21/2022 11:05 PM, Kalra, Ashish wrote:
> > > +static void do_exc_hv(struct pt_regs *regs)
> > > +{
> > > +    union hv_pending_events pending_events;
> > > +    u8 vector;
> > > +
> > > +    while (sev_hv_pending()) {
> > > +        asm volatile("cli" : : : "memory");
> > > +
> >
> > Do we really need to disable interrupts here, #HV exception will be 
> > dispatched via an interrupt gate in the IDT, so interrupts should be 
> > implicitly disabled, right ?
> > >    panic("Unexpected vector %d\n", vector);
> > > +                unreachable();
> > > +            }
> > > +        } else {
> > > +            common_interrupt(regs, pending_events.vector);
> > > +        }
> > > +
> > > +        asm volatile("sti" : : : "memory");
> >
> > Again, why do we need to re-enable interrupts here (in this loop), 
> > interrupts will get re-enabled in the irqentry_exit() code path ?
>
> Hi Ashish:
>      Thanks for your review.    check_hv_pending() is also called in the
> native_irq_enable() to handle some pending interrupt requests after re
> -enabling interrupt. For such case, disables irq when handle exception
> or interrupt event.

Then probably add the interrupt disable/enable in the caller
function like native_irq_enable() which seems logical as 
check_hv_pending() is always called with interrupts disabled (either via 
HW or SW) and also interrupt disable/enable seems redundant in 
check_hv_pending().

Thanks,
Ashish