linux-kernel - Re: [PATCH] xen/events: xen_evtchn_fifo

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Message-ID: <52E7C06F.3010205@linaro.org>
Date:	Tue, 28 Jan 2014 14:36:31 +0000
From:	Julien Grall <julien.grall@...aro.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	David Vrabel <david.vrabel@...rix.com>,
	linux-kernel@...r.kernel.org, konrad.wilk@...cle.com,
	boris.ostrovsky@...cle.com, xen-devel@...ts.xenproject.org,
	ian.campbell@...rix.com, patches@...aro.org
Subject: Re: [PATCH] xen/events: xen_evtchn_fifo_init can be called very late

On 01/28/2014 02:30 PM, Stefano Stabellini wrote:
> On Tue, 28 Jan 2014, David Vrabel wrote:
>> On 28/01/14 00:34, Julien Grall wrote:
>>> On ARM, xen_init_IRQ (which calls xen_evtchn_fifo_init) is called after
>>> all CPUs are online. It would mean that the notifier will never be called.
>>
>> Why does ARM call xen_init_IRQ() so late?  Is it possible to call it
>> earlier when only the boot CPU is online?  There are problems with
>> attempting to init FIFO event channels after all CPUs are online.
>>
>> If evtchn_fifo_init_control_block(cpu) fails on anything other than the
>> first CPU, that CPU will be unable to receive any events.  Xen will have
>> been switched to FIFO mode and it is not possible to revert back to
>> 2-level mode.
> 
> We simply didn't need to be called that early.
> Most of xen_guest_init could be moved to an early_initcall, if that is
> necessary.
> 

I'm actually working on a patch to move xen_init_IRQ() in early_initcall.

-- 
Julien Grall
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