Re: [[RFC PATCH 2/8]: PVH: changes related to initial boot and irq rewiring

[Ian Campbell <Ian.Campbell@citrix.com>]

> > > diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
> > > index 1573376..7c7dfd1 100644
> > > --- a/arch/x86/xen/irq.c
> > > +++ b/arch/x86/xen/irq.c
> > > @@ -100,6 +100,10 @@ PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
> > >  
> > >  static void xen_safe_halt(void)
> > >  {
> > > +	/* so event channel can be delivered to us, since in HVM
> > > container */
> > > +	if (xen_pvh_domain())
> > > +		local_irq_enable();
> > > +
> > >  	/* Blocking includes an implicit local_irq_enable(). */
> > 
> > So this comment isn't true for a PVH guest? Why not? Should it be?
>  
> I need to make sure the EFLAGS.IF is enabled. IIRC, the comment is saying
> that xen will clear event channel mask bit. For PVH, there's the additional
> EFLAGS.IF flag.
> 

My reading of the hypercall semantics would be that it reenables
whichever event delivery mechanism the guest is using and therefore it
should enable EFLAGS.IF for a PVH guest since manipulating the evtchn
mask in this case is pointless.

Ian.