Re: [PATCH v2 0/5] PCI: dwc: improve msi handling

Jon Hunter
2020-09-29T13:24:46Z

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