Re: [Xen-devel] [PATCH v4 16/16] xen/arm: add SGI handling for GICv3

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-06-02 at 17:05 +0100, Stefano Stabellini wrote:
> > +static int vgicv3_to_sgi(struct vcpu *v, register_t sgir)
> > +{
> > +    int virq;
> > +    int irqmode;
> > +    unsigned long vcpu_mask = 0;
> > +
> > +    irqmode = (sgir >> ICH_SGI_IRQMODE_SHIFT) & ICH_SGI_IRQMODE_MASK;
> > +    virq = (sgir >> ICH_SGI_IRQ_SHIFT ) & ICH_SGI_IRQ_MASK;
> > +    vcpu_mask = sgir & ICH_SGI_TARGETLIST_MASK;
> > +
> > +    return vgic_to_sgi(v, sgir, irqmode, virq, vcpu_mask);
> > +}
> 
> Given that we are not handling affinity 1, 2 and 3 settings, we should
> add an assert to make sure that they are 0.

Not literally an assert since that would give guests a trivial way to
DoS the system....

Given that we create guest VCPUs with MPIDR's which do not use
AFF{1,2,3} I think we can simply ignore any attempt to SGI those
processors, since they can't exist.

Of course this will mean implementing a 16 VCPU limit somewhere on the
creation side, so we actually do not create VCPUs with higher AFF's
used...

There should of course be a suitable comment both here and there...

Ian.


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