Messages in this thread |  | | Date | Tue, 29 Sep 2020 18:25:37 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v2 0/5] PCI: dwc: improve msi handling |
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On 2020-09-29 14:22, Jon Hunter wrote: > 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()?
The problem is common to all MSI implementations that end up muxing all the end-point MSIs into a single interrupt. With these systems, you cannot set the affinity of individual MSIs (they don't target a CPU, they target another interrupt... braindead). Only the mux interrupt can have its affinity changed.
So returning -EINVAL is the right thing to do.
M. -- Jazz is not dead. It just smells funny...
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