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From:   "hasegawa-hitomi@fujitsu.com" <hasegawa-hitomi@fujitsu.com>
To:     'Marc Zyngier' <maz@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Sumit Garg <sumit.garg@linaro.org>,
        "kernel-team@android.com" <kernel-team@android.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Russell King <linux@arm.linux.org.uk>,
        Jason Cooper <jason@lakedaemon.net>,
        Saravana Kannan <saravanak@google.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Gregory Clement <gregory.clement@bootlin.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will@kernel.org>,
        Valentin Schneider <Valentin.Schneider@arm.com>
Subject: RE: [PATCH v3 00/16] arm/arm64: Turning IPIs into normal interrupts
Thread-Topic: [PATCH v3 00/16] arm/arm64: Turning IPIs into normal interrupts
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Date:   Mon, 7 Sep 2020 06:06:12 +0000
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Hi Marc.

I am interested in this feature.
I have confirmed this patch works fine on Fujitsu FX1000. Thanks for creati=
ng it.
I look forward to the day when this patch is merged.
We plan to post a patch that implements IPI for CPU stop Interrupt (for cra=
sh dump) with pseudo NMI.

Tested-by: Hitomi Hasegawa <hasegwa-hitomi@fujitsu.com>
Thanks.

-----Original Message-----
From: linux-arm-kernel <linux-arm-kernel-bounces@lists.infradead.org> On Be=
half Of Marc Zyngier
Sent: Tuesday, September 1, 2020 11:43 PM
To: linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org
Cc: Sumit Garg <sumit.garg@linaro.org>; kernel-team@android.com; Florian Fa=
inelli <f.fainelli@gmail.com>; Russell King <linux@arm.linux.org.uk>; Jason=
 Cooper <jason@lakedaemon.net>; Saravana Kannan <saravanak@google.com>; And=
rew Lunn <andrew@lunn.ch>; Catalin Marinas <catalin.marinas@arm.com>; Grego=
ry Clement <gregory.clement@bootlin.com>; Thomas Gleixner <tglx@linutronix.=
de>; Will Deacon <will@kernel.org>; Valentin Schneider <Valentin.Schneider@=
arm.com>
Subject: [PATCH v3 00/16] arm/arm64: Turning IPIs into normal interrupts

For as long as SMP ARM has existed, IPIs have been handled as something spe=
cial. 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-specifi=
c interface instead of just implementing the base irqchip functionalities. =
The arch code also duplicates a number of things that the core irq code alr=
eady does (such as calling set_irq_regs(), irq_enter()...).

This series tries to remedy this on arm/arm64 by offering a new registratio=
n interface where the irqchip gives the arch code a range of interrupts to =
use for IPIs. The arch code requests these as normal per-cpu interrupts.

The bulk of the work is at the interrupt controller level, where all 5 irqc=
hips used on arm+SMP/arm64 get converted.

Finally, we drop the legacy registration interface as well as the custom st=
atistics accounting.

Note that I have had a look at providing a "generic" interface by expanding=
 the kernel/irq/ipi.c bag of helpers, but so far all irqchips have very dif=
ferent requirements, so there is hardly anything to consolidate for now. Ma=
ybe some as hip04 and the Marvell horror get cleaned up (the latter certain=
ly could do with a good dusting).

This has been tested on a bunch of 32 and 64bit guests (GICv2, GICv3), as w=
ell as 64bit bare metal (GICv3). The RPi part has only been tested in QEMU =
as a 64bit guest, while the HiSi and Marvell parts have only been compile-t=
ested.

I'm aiming for 5.10 for this, so any comment would be appreciated.

* From v2:
  - Tidied up the arch code (__read_mostly for the IPI handling data,
    WARN_ON_ONCE on setup and teardown), dropped spurious prototype
    on 32bit
  - Prevent IPIs from being forwarded to VCPUs
  - Merged the GIC affinity fix, hence one less patch
  - Added RBs from Valentin

* From v1:
  - Clarified the effect of nesting irq_enter/exit (Russell)
  - Changed the point where we tear IPIs down on (Valentin)
  - IPIs are no longer accessible from DT
  - HIP04 and Armada 370-XP have been converted, but are untested
  - arch-specific kstat accounting is removed
  - ARM's legacy interface is dropped

Marc Zyngier (16):
  genirq: Add fasteoi IPI flow
  genirq: Allow interrupts to be excluded from /proc/interrupts
  arm64: Allow IPIs to be handled as normal interrupts
  ARM: Allow IPIs to be handled as normal interrupts
  irqchip/gic-v3: Describe the SGI range
  irqchip/gic-v3: Configure SGIs as standard interrupts
  irqchip/gic: Refactor SMP configuration
  irqchip/gic: Configure SGIs as standard interrupts
  irqchip/gic-common: Don't enable SGIs by default
  irqchip/bcm2836: Configure mailbox interrupts as standard interrupts
  irqchip/hip04: Configure IPIs as standard interrupts
  irqchip/armada-370-xp: Configure IPIs as standard interrupts
  arm64: Kill __smp_cross_call and co
  arm64: Remove custom IRQ stat accounting
  ARM: Kill __smp_cross_call and co
  ARM: Remove custom IRQ stat accounting

 arch/arm/Kconfig                    |   1 +
 arch/arm/include/asm/hardirq.h      |  17 --
 arch/arm/include/asm/smp.h          |   5 +-
 arch/arm/kernel/smp.c               | 135 +++++++++-----
 arch/arm64/Kconfig                  |   1 +
 arch/arm64/include/asm/hardirq.h    |   9 -
 arch/arm64/include/asm/irq_work.h   |   4 +-
 arch/arm64/include/asm/smp.h        |   6 +-
 arch/arm64/kernel/smp.c             | 121 ++++++++-----
 drivers/irqchip/irq-armada-370-xp.c | 262 +++++++++++++++++++---------
 drivers/irqchip/irq-bcm2836.c       | 151 +++++++++++++---
 drivers/irqchip/irq-gic-common.c    |   3 -
 drivers/irqchip/irq-gic-v3.c        | 104 ++++++-----
 drivers/irqchip/irq-gic.c           | 177 +++++++++++--------
 drivers/irqchip/irq-hip04.c         |  89 +++++-----
 include/linux/irq.h                 |   5 +-
 kernel/irq/chip.c                   |  27 +++
 kernel/irq/debugfs.c                |   1 +
 kernel/irq/proc.c                   |   2 +-
 kernel/irq/settings.h               |   7 +
 20 files changed, 720 insertions(+), 407 deletions(-)

--
2.27.0


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