From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v2 06/21] xen/arm: Allow virq != irq
Date: Wed, 06 Aug 2014 16:07:23 +0100
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: xen-devel@lists.xenproject.org, tim@xen.org, ian.campbell@citrix.com, stefano.stabellini@citrix.com
List-Id: xen-devel@lists.xenproject.org

Hi Stefano,

On 08/06/2014 03:50 PM, Stefano Stabellini wrote:
>> -int route_irq_to_guest(struct domain *d, unsigned int irq,
>> -                       const char * devname)
>> +int route_irq_to_guest(struct domain *d, unsigned int virq,
>> +                       unsigned int irq, const char * devname)
>>  {
>>      struct irqaction *action;
>> -    struct irq_desc *desc = irq_to_desc(irq);
>> +    struct irq_guest *info;
>> +    struct irq_desc *desc;
>>      unsigned long flags;
>>      int retval = 0;
>>  
>>      action = xmalloc(struct irqaction);
>> -    if (!action)
>> +    if ( !action )
>> +        return -ENOMEM;
>> +
>> +    info = xmalloc(struct irq_guest);
>> +    if ( !info )
>> +    {
>> +        xfree(action);
>>          return -ENOMEM;
>> +    }
> 
> Rather than xmalloc'ing another struct and storing the pointer in
> dev_id, maybe we could simply expand struct arch_irq_desc?

I though about it. If we add another field in arch_irq_desc, we will
likely use more memory than xmalloc. This is because most of the
platform doesn't use 1024 interrupts but about 256 interrupts.

As the new field will be a pointer (on ARM64, 8 bytes), that would make
Xen use statically about 8K more.

We could allocate irq_desc dynamically during Xen boot.

Regards,

-- 
Julien Grall