Re: [Xen-devel] [PATCH for-4.6 4/4] xen/arm: Find automatically a PPI for the DOM0 event channel interrupt

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Stefano,

On 15/12/14 15:35, Stefano Stabellini wrote:
> On Fri, 12 Dec 2014, Julien Grall wrote:
>> Use the new vgic interface to know which virtual PPI is free and use it
>> for the event channel code.
>>
>> At the DOM0 creation time, Xen still don't know which vIRQ will be free.
>> All the vIRQ will be reserved when we parse the device tree. So allocate
>> when the hypervisor node is created.
>>
>> It's safe to defer the allocation because no vIRQ can be injected as
>> long as the vCPU is not online.
>>
>> Also correct the check in arch_domain_create to use is_hardware_domain.
>>
>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
>> ---
>>  xen/arch/arm/domain.c                | 13 ++++++++++---
>>  xen/arch/arm/domain_build.c          | 10 ++++++++++
>>  xen/arch/arm/platform.c              |  7 -------
>>  xen/arch/arm/platforms/xgene-storm.c |  1 -
>>  xen/include/asm-arm/platform.h       |  4 ----
>>  5 files changed, 20 insertions(+), 15 deletions(-)
>>
>> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
>> index 7221bc8..7d14377 100644
>> --- a/xen/arch/arm/domain.c
>> +++ b/xen/arch/arm/domain.c
>> @@ -543,10 +543,17 @@ int arch_domain_create(struct domain *d, unsigned int 
>> domcr_flags)
>>      if ( (rc = domain_vtimer_init(d)) != 0 )
>>          goto fail;
>>  
>> -    if ( d->domain_id )
>> +    /*
>> +     * The hardware domain will get a PPI later in
>> +     * arch/arm/domain_build.c  depending on the
>> +     * interrupt map of the hardware.
>> +     */
>> +    if ( !is_hardware_domain(d) )
>> +    {
>>          d->arch.evtchn_irq = GUEST_EVTCHN_PPI;
>> -    else
>> -        d->arch.evtchn_irq = platform_dom0_evtchn_ppi();
>> +        /* At this stage vgic_reserve_virq should never fail */
>> +        BUG_ON(vgic_reserve_virq(d, GUEST_EVTCHN_PPI));
>> +    }
> 
> Why do we still need this, if we have another vgic_allocate_virq call in
> make_hypervisor_node? Wouldn't that work for DomUs too?

Because make_hypervisor_node is only used for DOM0. Futhermore, DOMUs
are using a specific hardcoded layout (see xen/include/public/arch-arm.h).

Regards,

-- 
Julien Grall

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