From: Valentin Schneider <valentin.schneider@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Sumit Garg <sumit.garg@linaro.org>,
Florian Fainelli <f.fainelli@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
Jason Cooper <jason@lakedaemon.net>,
kernel-team@android.com, Andrew Lunn <andrew@lunn.ch>,
Catalin Marinas <catalin.marinas@arm.com>,
Gregory Clement <gregory.clement@bootlin.com>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 06/17] irqchip/gic-v3: Configure SGIs as standard interrupts
Date: Thu, 02 Jul 2020 15:24:30 +0100 [thread overview]
Message-ID: <jhjlfk28069.mognet@arm.com> (raw)
In-Reply-To: <1f3ac757acd15f6804917e222194c9cf@kernel.org>
On 02/07/20 14:48, Marc Zyngier wrote:
> On 2020-07-02 14:23, Valentin Schneider wrote:
>> On 30/06/20 11:15, Marc Zyngier wrote:
>>> On 2020-06-25 19:25, Valentin Schneider wrote:
>>>> Also, while staring at this it dawned on me that IPI's don't need the
>>>> eoimode=0 isb(): due to how the IPI flow-handler is structured, we'll
>>>> get a
>>>> gic_eoi_irq() just before calling into the irqaction. Dunno how much
>>>> we
>>>> care about it.
>>>
>>> That's interesting. This ISB is a leftover from the loop we had before
>>> the pseudo-NMI code, where we had to make sure the write to EOIR was
>>> ordered with the read from IAR.
>>>
>>> Given that we have an exception return right after the interrupt
>>> handling, I *think* we could get rid of it (but that would need
>>> mode checking on broken systems such as TX1...). I don't think
>>> this is specific to IPIs though.
>>>
>>
>> If I got this one right:
>>
>> 39a06b67c2c1 ("irqchip/gic: Ensure we have an ISB between ack and
>> ->handle_irq")
>>
>> you're describing case 2, which is indeed gone on gic-v3. However IIUC
>> we
>> also want an ISB between poking IAR and calling into the irqaction
>> (case 1)
>> - we get just that with IPIs due to the early gic_eoi_irq(), but we
>> don't
>> for the other flows.
>
> You just made me realise something amazing: I've started to forget about
> all this crap. Which is wonderful! ;-)
>
:)
> More seriously, you are absolutely right. If we wanted to address this,
> we'd probably have to give IPIs their own irqchip so that they get their
> own eoi callback. Not sure that's worth it.
>
I was initially thinking of something like
if (static_branch_likely(&supports_deactivate_key))
gic_write_eoir(irqnr);
else if (__get_intid_range(irqnr) != SGI_RANGE)
isb();
which is not particularly pretty, so maybe we should just slap this to the
isb():
/* Superfluous for SGIs, but who cares */
> M.
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next prev parent reply other threads:[~2020-07-02 14:25 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 19:57 [PATCH v2 00/17] arm/arm64: Turning IPIs into normal interrupts Marc Zyngier
2020-06-24 19:57 ` [PATCH v2 01/17] genirq: Add fasteoi IPI flow Marc Zyngier
2020-06-24 19:57 ` [PATCH v2 02/17] genirq: Allow interrupts to be excluded from /proc/interrupts Marc Zyngier
2020-06-24 19:57 ` [PATCH v2 03/17] arm64: Allow IPIs to be handled as normal interrupts Marc Zyngier
2020-06-25 18:25 ` Valentin Schneider
2020-07-10 19:58 ` Valentin Schneider
2020-06-24 19:57 ` [PATCH v2 04/17] ARM: " Marc Zyngier
2020-06-25 18:25 ` Valentin Schneider
2020-06-29 9:37 ` Marc Zyngier
2020-06-24 19:57 ` [PATCH v2 05/17] irqchip/gic-v3: Describe the SGI range Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 06/17] irqchip/gic-v3: Configure SGIs as standard interrupts Marc Zyngier
2020-06-25 18:25 ` Valentin Schneider
2020-06-30 10:15 ` Marc Zyngier
2020-07-02 13:23 ` Valentin Schneider
2020-07-02 13:48 ` Marc Zyngier
2020-07-02 14:24 ` Valentin Schneider [this message]
2020-06-24 19:58 ` [PATCH v2 07/17] irqchip/gic: Atomically update affinity Marc Zyngier
2020-07-01 19:33 ` Sasha Levin
2020-07-10 14:02 ` Sasha Levin
2021-09-09 15:22 ` Geert Uytterhoeven
2021-09-09 15:37 ` Russell King (Oracle)
2021-09-10 10:22 ` Marc Zyngier
2021-09-10 13:19 ` Geert Uytterhoeven
2021-09-11 2:49 ` Magnus Damm
2021-09-11 19:32 ` Marc Zyngier
2021-09-12 5:40 ` Magnus Damm
2021-09-13 8:05 ` Geert Uytterhoeven
2021-09-15 3:28 ` Magnus Damm
2020-06-24 19:58 ` [PATCH v2 08/17] irqchip/gic: Refactor SMP configuration Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 09/17] irqchip/gic: Configure SGIs as standard interrupts Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 10/17] irqchip/gic-common: Don't enable SGIs by default Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 11/17] irqchip/bcm2836: Configure mailbox interrupts as standard interrupts Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 12/17] irqchip/hip04: Configure IPIs " Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 13/17] irqchip/armada-370-xp: " Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 14/17] arm64: Kill __smp_cross_call and co Marc Zyngier
2020-06-25 18:25 ` Valentin Schneider
2020-07-02 13:37 ` Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 15/17] arm64: Remove custom IRQ stat accounting Marc Zyngier
2020-06-25 18:26 ` Valentin Schneider
2020-06-26 11:58 ` Marc Zyngier
2020-06-26 23:15 ` Valentin Schneider
2020-06-27 11:42 ` Marc Zyngier
2020-07-10 19:58 ` Valentin Schneider
2020-06-24 19:58 ` [PATCH v2 16/17] ARM: Kill __smp_cross_call and co Marc Zyngier
2020-06-24 19:58 ` [PATCH v2 17/17] ARM: Remove custom IRQ stat accounting Marc Zyngier
2020-06-25 18:24 ` [PATCH v2 00/17] arm/arm64: Turning IPIs into normal interrupts Valentin Schneider
2020-07-10 19:58 ` Valentin Schneider
2020-08-11 13:15 ` Sumit Garg
2020-08-11 13:58 ` Marc Zyngier
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