Re: [Xen-devel] [PATCH-4.5 3/4] xen/arm: do not request maintenance_interrupts

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 7 Feb 2014, Julien Grall wrote:
> On 07/02/14 18:56, Stefano Stabellini wrote:
>    > +static void gic_clear_lrs(struct vcpu *v)
> > +{
> > +    struct pending_irq *p;
> > +    int i = 0, irq;
> > +    uint32_t lr;
> > +    bool_t inflight;
> > +
> > +    ASSERT(!local_irq_is_enabled());
> > +
> > +    while ((i = find_next_bit((const long unsigned int *)
> > &this_cpu(lr_mask),
> > +                              nr_lrs, i)) < nr_lrs) {
> 
> Did you look at to ELRSR{0,1} registers which list the usable LRs? I think you
> can use it with the this_cpu(lr_mask) to avoid browsing every LRs.

Given that we only have 4 LR registers, I think that unconditionally
reading 2 ELRSR registers would cost more than simply checking lr_mask
on average.

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