Re: [Xen-devel] [PATCH v4 04/10] xen/arm: set GICH_HCR_UIE if all the LRs are in use

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 21 Mar 2014, Ian Campbell wrote:
> On Wed, 2014-03-19 at 12:31 +0000, Stefano Stabellini wrote:
> > On return to guest, if there are no free LRs and we still have more
> > interrupt to inject, set GICH_HCR_UIE so that we are going to receive a
> > maintenance interrupt when no pending interrupts are present in the LR
> > registers.
> 
> Should this go before the previous patch? Otherwise how to things work
> between #3 and #4? This would be harmless to go in first I think, apart
> from some spurious maintenance interrupts?

In practice you always receive timer interrupts so things would work
even without this patch.  However like you say moving this patch earlier
is harmless, so I'll do it.


> > The maintenance interrupt handler won't do anything anymore, but
> > receiving the interrupt is going to cause gic_inject to be called on
> > return to guest that is going to clear the old LRs and inject new
> > interrupts.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > ---
> > 
> > Changes in v2:
> > - disable/enable the GICH_HCR_UIE bit in GICH_HCR;
> > - only enable GICH_HCR_UIE if this_cpu(lr_mask) == ((1 << nr_lrs) - 1).
> > ---
> >  xen/arch/arm/gic.c |    6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> > index 32d3bea..d445e8b 100644
> > --- a/xen/arch/arm/gic.c
> > +++ b/xen/arch/arm/gic.c
> > @@ -790,6 +790,12 @@ void gic_inject(void)
> >          vgic_vcpu_inject_irq(current, current->domain->arch.evtchn_irq);
> >  
> >      gic_restore_pending_irqs(current);
> > +
> > +    if ( !list_empty(&current->arch.vgic.lr_pending) &&
> > +         this_cpu(lr_mask) == ((1 << nr_lrs) - 1) )
> > +        GICH[GICH_HCR] |= GICH_HCR_UIE;
> > +    else
> > +        GICH[GICH_HCR] &= ~GICH_HCR_UIE;
> >  }
> >  
> >  int gic_route_irq_to_guest(struct domain *d, const struct dt_irq *irq,
> 
> 

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