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From: Florian Fainelli <f.fainelli@gmail.com>
To: Marc Zyngier <maz@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Cc: Sumit Garg <sumit.garg@linaro.org>,
	Russell King <linux@arm.linux.org.uk>,
	Jason Cooper <jason@lakedaemon.net>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	kernel-team@android.com
Subject: Re: [PATCH 00/11] arm/arm64: Turning IPIs into normal interrupts
Date: Tue, 19 May 2020 12:47:44 -0700
Message-ID: <7b06f351-40f3-74c3-5d16-d7d58ab490b6@gmail.com> (raw)
In-Reply-To: <d1ac7873-0f02-dbe0-dd3c-4fd14a87cf03@gmail.com>



On 5/19/2020 10:50 AM, Florian Fainelli wrote:
> 
> 
> On 5/19/2020 9:17 AM, Marc Zyngier wrote:
>> For as long as SMP ARM has existed, IPIs have been handled as
>> something special. The arch code and the interrupt controller exchange
>> a couple of hooks (one to generate an IPI, another to handle it).
>>
>> Although this is perfectly manageable, it prevents the use of features
>> that we could use if IPIs were Linux IRQs (such as pseudo-NMIs). It
>> also means that each interrupt controller driver has to follow an
>> architecture-specific interface instead of just implementing the base
>> irqchip functionnalities. The arch code also duplicates a number of
>> things that the core irq code already does (such as calling
>> set_irq_regs(), irq_enter()...).
>>
>> This series tries to remedy this on arm/arm64 by offering a new
>> registration interface where the irqchip gives the arch code a range
>> of interrupts to use for IPIs. The arch code requests these as normal
>> interrupts.
>>
>> The bulk of the work is at the interrupt controller level, where all 3
>> irqchips used on arm64 get converted.
>>
>> Finally, the arm64 code drops the legacy registration interface. The
>> same thing could be done on 32bit as well once the two remaining
>> irqchips using that interface get converted.
>>
>> There is probably more that could be done: statistics are still
>> architecture-private code, for example, and no attempt is made to
>> solve that (apart from hidding the IRQs from /proc/interrupt).
>>
>> This has been tested on a bunch of 32 and 64bit guests.
> 
> Does this patch series change your position on this patch series
> 
> https://lore.kernel.org/linux-arm-kernel/20191023000547.7831-3-f.fainelli@gmail.com/T/
> 
> or is this still a no-no?

Our firmware specifies SGI interrupts with the first interrupt cell
specifier set to 2, so changing GIC_IRQ_TYPE_SGI to 2 allows me to use a
nearly unmodified firmware with your changes, sweet! I know this is not
supposed to be used that way, but the temptation was too big.

FWIW, on ARM64:

Tested-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

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Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 16:17 Marc Zyngier
2020-05-19 16:17 ` [PATCH 01/11] genirq: Add fasteoi IPI flow Marc Zyngier
2020-05-19 19:47   ` Florian Fainelli
2020-06-12  9:54     ` Marc Zyngier
2020-05-19 22:25   ` Valentin Schneider
2020-05-19 22:29     ` Valentin Schneider
2020-06-12  9:58     ` Marc Zyngier
2020-05-19 16:17 ` [PATCH 02/11] genirq: Allow interrupts to be excluded from /proc/interrupts Marc Zyngier
2020-05-19 16:17 ` [PATCH 03/11] arm64: Allow IPIs to be handled as normal interrupts Marc Zyngier
2020-05-21 14:03   ` Valentin Schneider
2020-05-19 16:17 ` [PATCH 04/11] ARM: " Marc Zyngier
2020-05-19 22:24   ` Russell King - ARM Linux admin
2020-05-21 14:03     ` Valentin Schneider
2020-05-21 15:12       ` Russell King - ARM Linux admin
2020-05-21 16:11         ` Valentin Schneider
2020-05-19 16:17 ` [PATCH 05/11] irqchip/gic-v3: Describe the SGI range Marc Zyngier
2020-05-19 16:17 ` [PATCH 06/11] irqchip/gic-v3: Configure SGIs as standard interrupts Marc Zyngier
2020-05-20  9:52   ` Sumit Garg
2020-05-20 10:24     ` Marc Zyngier
2020-05-21 14:04   ` Valentin Schneider
2020-06-12 10:39     ` Marc Zyngier
2020-05-19 16:17 ` [PATCH 07/11] irqchip/gic: Refactor SMP configuration Marc Zyngier
2020-05-19 16:17 ` [PATCH 08/11] irqchip/gic: Configure SGIs as standard interrupts Marc Zyngier
2021-04-20 20:37   ` dann frazier
2021-04-20 21:25     ` dann frazier
2021-04-21 10:58       ` Marc Zyngier
2021-04-21 14:52         ` dann frazier
2021-04-21 15:49           ` Marc Zyngier
2020-05-19 16:17 ` [PATCH 09/11] irqchip/gic-common: Don't enable SGIs by default Marc Zyngier
2020-05-19 16:17 ` [PATCH 10/11] irqchip/bcm2836: Configure mailbox interrupts as standard interrupts Marc Zyngier
2020-05-19 16:17 ` [PATCH 11/11] arm64: Kill __smp_cross_call and co Marc Zyngier
2020-05-19 17:50 ` [PATCH 00/11] arm/arm64: Turning IPIs into normal interrupts Florian Fainelli
2020-05-19 19:47   ` Florian Fainelli [this message]
2020-06-12  9:49   ` Marc Zyngier
2020-06-12 16:57     ` Florian Fainelli
2020-05-19 22:25 ` Valentin Schneider

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