linux-kernel - Re: [PATCH v3 00/16] arm/arm64: Turning IPIs into normal interrupts

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Date:   Wed, 16 Sep 2020 09:54:17 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Marc Zyngier <maz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Sumit Garg <sumit.garg@...aro.org>,
        Valentin Schneider <Valentin.Schneider@....com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Saravana Kannan <saravanak@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v3 00/16] arm/arm64: Turning IPIs into normal interrupts



On 9/1/2020 7:43 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 functionalities. 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
> per-cpu interrupts.
> 
> The bulk of the work is at the interrupt controller level, where all 5
> irqchips used on arm+SMP/arm64 get converted.
> 
> Finally, we drop the legacy registration interface as well as the
> custom statistics 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 different requirements, so there is hardly anything
> to consolidate for now. Maybe some as hip04 and the Marvell horror get
> cleaned up (the latter certainly could do with a good dusting).
> 
> This has been tested on a bunch of 32 and 64bit guests (GICv2, GICv3),
> as well 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-tested.
> 
> I'm aiming for 5.10 for this, so any comment would be appreciated.

FWIW, I boot tested this on a Brahma-B53 device (GIC-400) in 32-bit and 
64-bit mode and on a Brahma-B15 device (GIC-400 as well) and both 
devices worked in all 3 configurations:

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

All cores were brought up successfully. All of these devices use 
PSCI/ATF FWIW.
-- 
Florian