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Subject: Re: [PATCH v2 0/5] PCI: dwc: improve msi handling
To:     Jisheng Zhang <Jisheng.Zhang@synaptics.com>
CC:     Kishon Vijay Abraham I <kishon@ti.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
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References: <20200924190421.549cb8fc@xhacker.debian>
 <de4d9294-4f6d-c7d1-efc7-c8ef6570bd64@nvidia.com>
 <20200929184851.22682ff1@xhacker.debian>
From:   Jon Hunter <jonathanh@nvidia.com>
Message-ID: <8e06a370-a37a-5f33-b43b-2830adb31b3e@nvidia.com>
Date:   Tue, 29 Sep 2020 14:22:57 +0100
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Hi Jisheng,

On 29/09/2020 11:48, Jisheng Zhang wrote:
> Hi Jon,
> 
> On Fri, 25 Sep 2020 09:53:45 +0100 Jon Hunter wrote:
> 
>>
>> On 24/09/2020 12:05, Jisheng Zhang wrote:
>>> Improve the msi code:
>>> 1. Add proper error handling.
>>> 2. Move dw_pcie_msi_init() from each users to designware host to solve
>>> msi page leakage in resume path.  
>>
>> Apologies if this is slightly off topic, but I have been meaning to ask
>> about MSIs and PCI. On Tegra194 which uses the DWC PCI driver, whenever we
>> hotplug CPUs we see the following warnings ...
>>
>>  [      79.068351] WARNING KERN IRQ70: set affinity failed(-22).
>>  [      79.068362] WARNING KERN IRQ71: set affinity failed(-22).
>>
> 
> I tried to reproduce this issue on Synaptics SoC, but can't reproduce it.
> Per my understanding of the code in kernel/irq/cpuhotplug.c, this warning
> happened when we migrate irqs away from the offline cpu, this implicitly
> implies that before this point the irq has bind to the offline cpu, but how
> could this happen given current dw_pci_msi_set_affinity() implementation
> always return -EINVAL

By default the smp_affinity should be set so that all CPUs can be
interrupted ...

$ cat /proc/irq/70/smp_affinity
0xff

In my case there are 8 CPUs and so 0xff implies that the interrupt can
be triggered on any of the 8 CPUs.

Do you see the set_affinity callback being called for the DWC irqchip in
migrate_one_irq()?

Cheers
Jon

-- 
nvpublic