Re: [PATCH] x86: fix probe_nr_irqs for xen

[Jeremy Fitzhardinge <jeremy@goop.org>]

Yinghai Lu wrote:
> On Thu, Aug 21, 2008 at 4:33 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>   
>> Yinghai Lu wrote:
>>     
>>> otherwise Xen is _completely_ unusable with 5 or more VCPUs.
>>> ( when !CONFIG_HAVE_SPARSE_IRQ)
>>>
>>> based on Alex's patch
>>>
>>> also add +1 offset after redir_entries
>>>
>>> Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
>>> Cc: Alex Nixon <alex.nixon@citrix.com>
>>>
>>>       
>> Looks good to me.  We can fix this in a better way later.
>>     
>
> later could set CONFIG_HAVE_SPARSE_IRQ to true by default.
>   

Well, perhaps.  But we can use vectors rather than IRQs for Xen event
channel mappings, which will save us from having to allocate lots of
per-cpu irqs.

Also, implementing probe_nr_irqs() in a more generic (rather than
io_apic-specific) way.  Using some interface that queries each irq chip
for how many irqs it supports, or something.

    J