linux-kernel - Re: TARGET_CPUS in assign_irq

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Message-ID: <86802c440809091824u715ef2a0o6dc772f66212c38f@mail.gmail.com>
Date:	Tue, 9 Sep 2008 18:24:03 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: TARGET_CPUS in assign_irq_vector

On Tue, Sep 9, 2008 at 5:50 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> Yinghai Lu wrote:
>> On Tue, Sep 9, 2008 at 4:46 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>>
>>> Yinghai Lu wrote:
>>>
>>>> target_cpus is the cpus that could be possible to used to take vector
>>>> and process that irq. so at least it should be online.
>>>>
>>>>
>>> Would it be wrong to make it possible_cpu_mask?
>>>
>>>
>> it is wrong
>
> What happens if you online a new cpu and migrate the irq to it?  Does it
> get allocated a new vector?

for phys_flat mode: it will get new vector for on new cpu.

>
> I'm using create_irq() as a general irq and vector allocation mechanism
> for Xen interrupts.  I'd like to be able to allocate a vector across all
> possible cpus so I can bind Xen event channels to vectors.  Should I: 1)
> add a create_irq_cpus() which takes a cpu mask rather than defaulting to
> TARGET_CPUS, 2) modify struct genapic to insert by own target_cpus(),
> 3) give up because the idea is fundamentally ill-conceived, or 4)
> something else?

seems need to rework __assign_irq_vector a little bit.

to
cpumask_t (*vector_allocation_domain_t)(int cpu)
static int __assign_irq_vector(int irq, cpumask_t mask,
vector_allocation_domain_t p)

...

and you could have your own

static cpumask_t vec_domain_alloc(int cpu)
{
        cpumask_t domain = cpu_possible_map;
        return domain;
}


static int assign_irq_vector_all(int irq)
{
        int err;
        unsigned long flags;
        cpumask_t mask = cpu_possible_map;

        spin_lock_irqsave(&vector_lock, flags);
        err = __assign_irq_vector(irq, mask, vec_domain_alloc);
        spin_unlock_irqrestore(&vector_lock, flags);
        return err;
}

YH
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