linux-kernel - Re: [RFC PATCH 03/23] genirq: Introduce IRQF_DELIVER_AS

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Date:   Wed, 13 Jun 2018 11:25:18 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Borislav Petkov <bp@...e.de>,
        Tony Luck <tony.luck@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>, x86@...nel.org,
        sparclinux@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Jacob Pan <jacob.jun.pan@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Doug Berger <opendmb@...il.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        iommu@...ts.linux-foundation.org
Subject: Re: [RFC PATCH 03/23] genirq: Introduce IRQF_DELIVER_AS_NMI



On 13/06/18 10:57, Thomas Gleixner wrote:
> On Wed, 13 Jun 2018, Julien Thierry wrote:
>> On 13/06/18 10:20, Thomas Gleixner wrote:
>>> Adding NMI delivery support at low level architecture irq chip level is
>>> perfectly fine, but the exposure of that needs to be restricted very
>>> much. Adding it to the generic interrupt control interfaces is not going to
>>> happen. That's doomed to begin with and a complete abuse of the interface
>>> as the handler can not ever be used for that.
>>>
>>
>> Understood, however the need would be to provide a way for a driver to request
>> an interrupt to be delivered as an NMI (if irqchip supports it).
> 
> s/driver/specialized code written by people who know what they are doing/
> 
>> But from your response this would be out of the question (in the
>> interrupt/irq/irqchip definitions).
> 
> Adding some magic to the irq chip is fine, because that's where the low
> level integration needs to be done, but exposing it through the generic
> interrupt subsystem is a NONO for obvious reasons.
> 
>> Or somehow the concerned irqchip informs the arch it supports NMI delivery and
>> it is up to the interested drivers to query the arch whether NMI delivery is
>> supported by the system?
> 
> Yes, we need some infrastructure for that, but that needs to be separate
> and with very limited exposure.
> 

Right, makes sense. I'll check with Marc how such an infrastructure 
should be introduced.

Thanks,

-- 
Julien Thierry