Re: [Xen-devel] [PATCH] x86/vm_event: block interrupt injection for sync vm_events

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.12.18 at 21:48, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> Block interrupts (in vmx_intr_assist()) for the duration of
> processing a sync vm_event (similarly to the strategy
> currently used for single-stepping). Otherwise, attempting
> to emulate an instruction when requested by a vm_event
> reply may legitimately need to call hvm_inject_page_fault(),
> which then overwrites the active interrupt in the VMCS.

I take it that hvm_inject_page_fault() is just the most prominent
example. If so, wold you mind adding "e.g."?

> @@ -239,6 +241,12 @@ void vmx_intr_assist(void)
>          return;
>      }
>  
> +    /* Block event injection while handling a sync vm_event. */
> +    if ( unlikely(v->arch.vm_event) &&
> +         vm_event_check_ring(v->domain->vm_event_monitor) &&

Is this check really needed?

> +         v->arch.vm_event->intr_block )

This part certainly doesn't look to depend on it. Perhaps
->intr_block would better be cleared when tearing down a ring?

Also is there really no similar change needed on the AMD (SVM)
side?

Jan



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