Re: xen/arm: Query - vgic nr_spis value for domU

[Ian Campbell <ian.campbell@citrix.com>]

On Tue, 2015-02-24 at 14:54 +0530, Vijay Kilari wrote:
> Hi,
> 
> In the below snippet, nr_spis is set to 0 from domU based on this
> pending_irq[] is allocated
> 
> int domain_vgic_init(struct domain *d)
> {
>     ....
>     if ( is_hardware_domain(d) )
>         d->arch.vgic.nr_spis = gic_number_lines() - 32;
>     else
>         d->arch.vgic.nr_spis = 0; /* We don't need SPIs for the guest */
>     ...
> 
> }
> 
> Does it mean that no devices are attached to domU. So spis are required?
> If so, for device pass-through (non-pci) how is it managed?

Julien's non-pci passthrough series makes this configurable at domain
creation time.

> For pci-passthrough I am assigning non-zero value to nr_lpis for both
> domU & dom0
> and allocating pending_lpis[] because MSIx are assigned to domU
> directly on ITS commands
> trapped from domain.
> 
> Do you see any issue with this?

dom0 should get the underlying h/w platforms value for nr_*, including
spi and lpi

domU should get configurable nr_lpi in the same way Julien has done for
spi. Unless it is possible to make nr_lpi dynamic based on the guests
actual usage patterns (i.e. alloc on demand), that would be ok too.

Ian.