Re: [Xen-devel] [PATCH 11/28] ARM: GICv3: forward pending LPIs to guests

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 14/02/17 21:00, Stefano Stabellini wrote:
> On Mon, 30 Jan 2017, Andre Przywara wrote:
> > +/*
> > + * Handle incoming LPIs, which are a bit special, because they are potentially
> > + * numerous and also only get injected into guests. Treat them specially here,
> > + * by just looking up their target vCPU and virtual LPI number and hand it
> > + * over to the injection function.
> > + */
> > +void do_LPI(unsigned int lpi)
> > +{
> > +    struct domain *d;
> > +    union host_lpi *hlpip, hlpi;
> > +    struct vcpu *vcpu;
> > +
> > +    WRITE_SYSREG32(lpi, ICC_EOIR1_EL1);
> > +
> > +    hlpip = gic_get_host_lpi(lpi);
> > +    if ( !hlpip )
> > +        return;
> > +
> > +    hlpi.data = read_u64_atomic(&hlpip->data);
> > +
> > +    /* We may have mapped more host LPIs than the guest actually asked for. */
> > +    if ( !hlpi.virt_lpi )
> > +        return;
> > +
> > +    d = get_domain_by_id(hlpi.dom_id);
> > +    if ( !d )
> > +        return;
> > +
> > +    if ( hlpi.vcpu_id >= d->max_vcpus )
> > +    {
> > +        put_domain(d);
> > +        return;
> > +    }
> > +
> > +    vcpu = d->vcpu[hlpi.vcpu_id];
> > +
> > +    put_domain(d);
> > +
> > +    vgic_vcpu_inject_irq(vcpu, hlpi.virt_lpi);
> put_domain should be here
Why? I don't even understand why we would need to take a reference on 
the domain for LPIs. Would not it be enough to use rcu_lock_domain_by_id 
here?
Regards,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel