Re: [Xen-devel] [PATCH v8 18/27] ARM: vITS: handle MAPD command

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 12/04/17 18:03, Andre Przywara wrote:
> On 12/04/17 16:21, Julien Grall wrote:
> > On 12/04/17 01:44, Andre Przywara wrote:
> > > +
> > > +    spin_unlock_irqrestore(&vcpu->arch.vgic.lock, flags);
> > > +
> > > +    /* Remove the corresponding host LPI entry */
> > > +    return gicv3_remove_guest_event(its->d, its->doorbell_address,
> > > +                                    vdevid, vevid);
> > > +}
> > > +
> > > +static int its_unmap_device(struct virt_its *its, uint32_t devid)
> > > +{
> > > +    uint64_t itt, evid;
> > > +    int ret;
> > > +
> > > +    spin_lock(&its->its_lock);
> > > +
> > > +    ret = its_get_itt(its, devid, &itt);
> > > +    if ( ret )
> > > +    {
> > > +        spin_unlock(&its->its_lock);
> > > +        return ret;
> > > +    }
> > > +
> > > +    for ( evid = 0; evid < DEV_TABLE_ITT_SIZE(itt); evid++ )
> > > +        /* Don't care about errors here, clean up as much as
> > > possible. */
> > > +        its_discard_event(its, devid, evid);
> > > +
> > > +    spin_unlock(&its->its_lock);
> > This code can be long to execute as the number of event can be huge. How
> > do you plan to handle that?
> It is assumed that DomUs get only a *very* limited and controlled number
> of ITS resources, so the number of LPIs, number of devices and their
> number of events will be very small, probably just enough as really
> needed (event ID bits being 4 or so, for instance).
I really doubt this. I would not be surprised to see PCI device 
passthrough with hundreds of event. And then we will have a beloved XSA 
to handle...
> > *hint* this likely means a comment + ASSERT + TODO in the cover letter
> > *hint*
> Added.
Cheers,

--
Julien Grall

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