linux-kernel - Re: [PATCH 3/5] irqchip/bcm2836: Make IPIs use handle_percpu_devid

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Message-ID: <26426427-3459-6eb9-42fe-d7406bcf2b14@roeck-us.net>
Date:   Tue, 15 Dec 2020 08:23:23 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Andrew Lunn <andrew@...n.ch>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Scott Branden <sbranden@...adcom.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH 3/5] irqchip/bcm2836: Make IPIs use
 handle_percpu_devid_irq()

On 12/15/20 7:46 AM, Marc Zyngier wrote:
> On 2020-12-15 15:39, Guenter Roeck wrote:
>> On 12/15/20 7:26 AM, Marc Zyngier wrote:
>>> On 2020-12-15 15:21, Guenter Roeck wrote:
>>>> Hi Marc,
>>>>
>>>> On 12/15/20 2:19 AM, Marc Zyngier wrote:
>>>>> Hi Gunter,
>>>>>
>>>>> On 2020-12-15 00:21, Guenter Roeck wrote:
>>>>>> On Mon, Nov 09, 2020 at 09:41:19AM +0000, Valentin Schneider wrote:
>>>>>>> As done for the Arm GIC irqchips, move IPIs to handle_percpu_devid_irq() as
>>>>>>> handle_percpu_devid_fasteoi_ipi() isn't actually required.
>>>>>>>
>>>>>>> Signed-off-by: Valentin Schneider <valentin.schneider@....com>
>>>>>>
>>>>>> This patch results in boot failures (silent stall) for the qemu
>>>>>> raspi2 emulation. Unfortunately it can not be reverted because
>>>>>> handle_percpu_devid_fasteoi_ipi no longer exists in next-20201214,
>>>>>> so I don't know if it is the only problem.
>>>>>
>>>>> This is odd. This works just fine for me on both the RPi2 and 3
>>>>> emulation, running a full Debian userspace. Could this be caused
>>>>> by the version of QEMU you are using? Here's what I have:
>>>>>
>>>>> $ qemu-system-arm --version
>>>>> QEMU emulator version 5.1.0 (Debian 1:5.1+dfsg-4+b1)
>>>>>
>>>>
>>>> I used qemu 5.0 which - up to now - worked fine. Let me try with
>>>> 5.1 and 5.2. Sorry, I should have tried first before bothering you.
>>>
>>> No bother at all. If this works for you on more recent versions of
>>> QEMU, that'd be an interesting data point. I'm also interested in
>>> the result of the patch either way.
>>>
>>
>> It doesn't work for me with qemu 5.1, nor with qemu 5.2. My userspace
>> is generated with buildroot, busybox-based, and very basic.
> 
> OK, so something is definitely different between our setups.
> Mind pointing me to your config and your QEMU invocation?
> 

Configuration is multi_v7_defconfig with various additional options enabled.
You'll find it attached.

qemu invocation:

qemu-system-arm -M raspi2 -kernel arch/arm/boot/zImage -no-reboot
    -initrd  /var/cache/buildbot/arm/rootfs-armv7a.cpio
    --append "panic=-1 slub_debug=FZPUA rdinit=/sbin/init earlycon=pl011,0x3f201000 console=ttyAMA0"
    -dtb arch/arm/boot/dts/bcm2836-rpi-2-b.dtb -nographic -monitor null -serial stdio

initrd is from:
    https://github.com/groeck/linux-build-test/blob/master/rootfs/arm/rootfs-armv7a.cpio.gz

Without your patch, boot always stalls at:

[   10.197299] PCI: CLS 0 bytes, default 64
[   10.210594] Trying to unpack rootfs image as initramfs...
[   10.573055] Freeing initrd memory: 3256K
[   10.581294] hw perfevents: enabled with armv7_cortex_a7 PMU driver, 5 counters available

With your patch applied, it proceeds:

[    9.594508] PCI: CLS 0 bytes, default 64
[    9.603180] Trying to unpack rootfs image as initramfs...
[    9.987446] Freeing initrd memory: 3256K
[   10.000387] hw perfevents: enabled with armv7_cortex_a7 PMU driver, 5 counters available
[   17.180317] Initialise system trusted keyrings
[   17.184302] workingset: timestamp_bits=30 max_order=18 bucket_order=0
[   17.428873] squashfs: version 4.0 (2009/01/31) Phillip Lougher
...

Guenter

View attachment "defconfig" of type "text/plain" (27964 bytes)