linux-kernel - Re: [PATCH kernel v3] genirq/irqdomain: Add reference counting to IRQs

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Message-ID: <258becba10679166555137c7f2727265@kernel.org>
Date:   Sat, 14 Nov 2020 11:37:57 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Cédric Le Goater <clg@...d.org>,
        Michael Ellerman <mpe@...erman.id.au>, Qian Cai <cai@....pw>,
        Rob Herring <robh@...nel.org>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Michal Suchánek <msuchanek@...e.de>
Subject: Re: [PATCH kernel v3] genirq/irqdomain: Add reference counting to
 IRQs

On 2020-11-14 03:37, Alexey Kardashevskiy wrote:

>>> What is the easiest way to get irq-hierarchical hardware?
>>> I have a bunch of powerpc boxes (no good) but also a raspberry pi,
>>> a bunch of 32/64bit orange pi's, an "armada" arm box,
>>> thinkpads - is any of this good for the task?
>> 
>> If your HW doesn't require an interrupt hierarchy, run VMs!
>> Booting an arm64 guest with virtual PCI devices will result in
>> hierarchies being created (PCI-MSI -> GIC MSI widget -> GIC).
> 
> Absolutely :) But the beauty of ARM is that one can buy an actual ARM
> device for 20$, I have "opi one+ allwinner h6 64bit cortex a53 1GB
> RAM", is it worth using KVM on this device, or is it too small for
> that?

I've run VMs on smaller machines. 256MB of guest RAM is enough to boot
a full blown Debian system with PCI devices, and your AW box should be
up to the task as long as you run a mainline kernel on it. Please don't
add to the pile of junk!

>> You can use KVM, or even bare QEMU on x86 if you are so inclined.
> 
> Have a QEMU command line handy for x86/tcg?

/me digs, as my x86 boxes are overspec'd X terminals these days:

Here you go, courtesy of Will:
http://cdn.kernel.org/pub/linux/kernel/people/will/docs/qemu/qemu-arm64-howto.html

         M.
-- 
Jazz is not dead. It just smells funny...