Re: [Xen-devel] [PATCH 05/11] xen/arm: vpl011: Initialize nr_spis in vgic_init in Xen to atleast 1

[Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx>]

On 16 March 2017 at 18:54, Julien Grall <julien.grall@xxxxxxx> wrote:
> Hi Bhupinder,
>
> On 03/16/2017 10:31 AM, Bhupinder Thakur wrote:
>>
>> On 16 March 2017 at 13:54, Julien Grall <julien.grall@xxxxxxx> wrote:
>>>>
>>>>
>>>> The other option is to reserve a SPI for pl011 at compile time and use
>>>> that value. Let me know.
>>>
>>>
>>>
>>> Whilst I am ok to have the pl011 SPI number hardcoded, I don't like the
>>> approach taken in this patch because the toolstack is in charge of the
>>> guest
>>> layout (interrupt, memory...) and not the hypervisor.
>>>
>>> The values are hardcoded today because we decided to do a fix layout for
>>> simplicity. It is likely to be changed in the future.
>>>
>>> The toolstack knows how much memory the user requested, the list of
>>> devices
>>> available... So it is the goal of the toolstack to bump the number of
>>> SPIs
>>> before creating the domain if a PL011 will be exposed.
>>>
>>> Also, the interaction between the pl011 and the parameter "irqs" in the
>>> domain configuration file will need to be documented. By that I mean
>>> explaining from which number the SPIs will be allocated when choosing a
>>> pl011 enabling.
>>>
>>> Note the probably want to allow the user to choose the pl011 IRQ and MMIO
>>> region. If he doesn't provide any, we would use the default value.
>>>
>>> Cheers,
>>
>>
>> We can follow the convention that when pl011 is enabled then the last
>> irq in the "irqs" list will be used as the pl011 irq. I believe that
>> the irqs mentioned in the "irqs" list will be reserved by the
>> hypervisor when the domain is created and we need not allocate a SPI
>> separately as we are doing currently.
>
>
> I don't understand what you mean here. If you speak about the xl parameter
> "irqs", it is a list of physical IRQs and not virtual IRQs. Furthermore, we
> would like to keep to avoid a normal user to do more than specifying "pl011"
> or else on in the guest configuration file.
>
> So could you clarify what you mean?
>

Now, I am taking one option in the domU configuration file which tells
whether pl011 emulation is enabled or not. Based on this option, the
tool stack will increment the nr_spis (i have removed the nr_spis
increment logic from the hypervisor code). It will create the pl011 DT
node also based on whether this option is enabled.

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