Re: [Xen-devel] [PATCH 4/5] xen/arm: use the physical number of gic lines for boot domains

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 15 Jan 2019, Julien Grall wrote:
> Hi Stefano,
> 
> On 1/3/19 7:07 PM, Stefano Stabellini wrote:
> > On Mon, 24 Dec 2018, Julien Grall wrote:
> > > Hi,
> > > 
> > > On 12/5/18 5:28 PM, Stefano Stabellini wrote:
> > > > We don't have a clear way to know how many virtual SPIs we need for the
> > > > boot domains. For simplicity, allocate as many as natively supported,
> > > > just like for dom0.
> > > 
> > > This will potentially allocate a lot of unused interrupts and a waste of
> > > memory. So is it the correct solution?
> > > 
> > > For instance, we would request the user to provide the number of
> > > interrupts.
> > 
> > Unfortunately, this has to happen much earlier than when we parse user
> > supplied device tree options. We could make it an hypervisor command
> > line parameter but it would be nasty.
> 
> Why does this value needs to be in the supplied device-tree. Can't it be part
> of the node in the host DT?

You mean as an option under the xen,domain node? Yes, I think that would
be possible. Like:

 nr_spis = <0x64>;

And if it is missing we default back to gic_number_lines() - 32. That
could be a good idea.


> > Given that this feature is aimed at partitioning scenarios where the
> > number of VMs is low, the increased memory overhead is not a big issue.
> 
> Please write it down in the commit message.
 
I will


> > (If you recall we briefly discussed this topic at the last Linaro
> > Connect, this was the conclusion.)


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