From: ebiederm@xmission•com (Eric W. Biederman)
To: Ian Campbell <Ian.Campbell@citrix•com>
Cc: Jeremy Fitzhardinge <jeremy@goop•org>,
"x86@kernel•org" <x86@kernel•org>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>,
"linuxppc-dev@ozlabs•org" <linuxppc-dev@ozlabs•org>,
Ingo Molnar <mingo@redhat•com>, Paul Mackerras <paulus@samba•org>,
"H. Peter Anvin" <hpa@zytor•com>,
Thomas Gleixner <tglx@linutronix•de>,
Yinghai Lu <yinghai@kernel•org>
Subject: Re: [PATCH] irq: move some interrupt arch_* functions into struct irq_chip.
Date: Wed, 10 Mar 2010 09:42:08 -0800 [thread overview]
Message-ID: <m1iq94gjkf.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <1268225473.11737.69196.camel@zakaz.uk.xensource.com> (Ian Campbell's message of "Wed\, 10 Mar 2010 12\:51\:13 +0000")
Ian Campbell <Ian.Campbell@citrix•com> writes:
> On Wed, 2010-03-10 at 12:06 +0000, Yinghai Lu wrote:
>> On Wed, Mar 10, 2010 at 2:55 AM, <ijc@hellion•org.uk> wrote:
>> > From: Ian Campbell <ian.campbell@citrix•com>
>> >
>> > Move arch_init_copy_chip_data and arch_free_chip_data into function
>> > pointers in struct irq_chip since they operate on irq_desc->chip_data.
>> >
>> > arch_init_chip_data cannot be moved into struct irq_chip at this time
>> > because irq_desc->chip is not known at the time the irq_desc is
>> > setup. For now rename arch_init_chip_data to arch_init_irq_desc (for
>> > PowerPC, the only other user, whose usage better matches the new name)
>> > and on x86 convert arch_init_chip_data to ioapic_init_chip_data and
>> > call this whenever the IO APIC code allocates a new IRQ.
>> >
>> > I've retained the chip_data behaviour for uv_irq although it isn't
>> > clear to me if these interrupt types support migration or how closely
>> > related to the APIC modes they really are. If it weren't for this the
>> > ioapic_{init,copy,free}_chip_data functions could be static to
>> > io_apic.c.
>> >
>> > I've tested by booting on a 64 bit system, but it's not clear to me
>> > what actions I need to take to actually exercise some of these code
>> > paths.
>> >
>>
>> can you just add another pointer field in irq_desc?
>>
>> some kind of *irq_info etc.
>
> I think I don't understand what you are suggesting.
YH another field doesn't make much sense. Xen is a bizarre subarch
with an incompatible irq model. Xen simply needs the ability to
handle the entire lifetime of an irq_chip.
All we need between the Xen and the rest of x86 is a convention
so that we never manage the same irqs. At least for domU we are
in an either/or situation so I don't see even that being a problem.
> There is already a pointer for irq_chip specific use i.e.
> irq_desc->chip_data. This patchset is just about ensuring that the field
> really is available to any chip implementation rather than just assuming
> it is always used for the acpi chip types (on x86 at least).
Ian Xen in this sense is simply not x86. irq_cfg is not acpi or ioapic
or anything but x86 specific. It has everything to do with having a per
cpu vector table of 256 entries and architecturally receiving a vector
number when an interrupt is fired.
It totally makes sense for Xen to do something different because
architecturally it has a completely different irq subsystem.
At the same time let's not pretend that the reason for this is anything
except that Xen has a completely different notion of interrupt delivery
than the rest of x86 and so it is it's own bizarre subarch.
This is not a case where you simply need a driver because something is
a bit different but fits into the existing model.
So the best solution here seems to be a parameter that we pass into
irq_to_desc_alloc_node that does what is needed. The second best
would be to have arch_init_chip_data to call something like
platfrom_init_chip_data(). But I think we can avoid that in
this case.
Eric
next prev parent reply other threads:[~2010-03-10 17:42 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1268218524.11737.68547.camel@zakaz.uk.xensource.com>
2010-03-10 10:55 ` [PATCH] irq: move some interrupt arch_* functions into struct irq_chip ijc
2010-03-10 11:00 ` Ian Campbell
2010-03-10 17:18 ` Eric W. Biederman
2010-03-10 17:41 ` Ian Campbell
2010-03-10 18:11 ` Eric W. Biederman
2010-03-10 12:06 ` Yinghai Lu
2010-03-10 12:51 ` Ian Campbell
2010-03-10 17:42 ` Eric W. Biederman [this message]
2010-03-10 17:50 ` Ian Campbell
2010-03-10 18:15 ` Eric W. Biederman
2010-03-10 18:28 ` Ian Campbell
2010-03-10 18:27 ` Jeremy Fitzhardinge
2010-03-10 18:59 ` Yinghai Lu
2010-03-10 19:15 ` Eric W. Biederman
2010-03-10 22:07 ` Michael Ellerman
2010-03-12 9:44 [GITPULL+PATCH 0/2] " Ian Campbell
2010-03-12 9:45 ` [PATCH] " Ian Campbell
2010-03-12 19:26 ` Yinghai Lu
2010-03-13 0:29 ` Eric W. Biederman
2010-03-16 8:50 ` Ian Campbell
2010-03-16 9:18 ` Eric W. Biederman
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