linux-kernel - Re: MSI interrupt for xhci still lost on 5.6-rc6 after cpu hotplug

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Date:   Wed, 25 Mar 2020 19:12:20 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Evan Green <evgreen@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     x86@...nel.org, linux-pci <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Ghorai, Sukumar" <sukumar.ghorai@...el.com>,
        "Amara, Madhusudanarao" <madhusudanarao.amara@...el.com>,
        "Nandamuri, Srikanth" <srikanth.nandamuri@...el.com>
Subject: Re: MSI interrupt for xhci still lost on 5.6-rc6 after cpu hotplug

On 24.3.2020 18.17, Evan Green wrote:
> 
> Another experiment would be to try my old patch in [1]. I'm not
> advocating for this patch as a solution, Thomas and Bjorn have
> convinced me that it will break the rest of the world. But your PCI
> device 0xa3af seems to be Comet Lake. I was also on Comet Lake. So I'd
> expect to at least see it mask your problem. Again, if it didn't, that
> might be an interesting datapoint.
> 
> [1] https://lore.kernel.org/lkml/20200117162444.v2.1.I9c7e72144ef639cc135ea33ef332852a6b33730f@changeid/
> 

Yes I'm testing on a Comet Lake, oddly your patch doesn't mask the problem.
Did a few rounds, seems that xhci interrupts don't always stop when both vector
and apicid are updated. Sometimes just apicid update triggers it.

(tail of) round 1:
          <idle>-0     [001] d.h.   249.040051: xhci_irq: xhci irq
          <idle>-0     [001] d.h.   249.040122: do_IRQ: vector: 33 desc ffff9e84075b1800
          <idle>-0     [001] d.h.   249.040125: xhci_irq: xhci irq
     migration/1-14    [001] d..1   249.045231: msi_set_affinity: direct update msi 123, vector 33 -> 33, apicid: 2 -> 6
     migration/3-24    [003] d..1   249.069563: msi_set_affinity: twostep update msi, irq 123, vector 33 -> 35, apicid: 6 -> 0
          <idle>-0     [000] d.h.   250.294934: do_IRQ: vector: 33 desc ffff9e84066df200
          <idle>-0     [000] d.h.   250.294940: msi_set_affinity: direct update msi 122, vector 33 -> 33, apicid: 0 -> 0
          <idle>-0     [000] d.h.   252.276099: do_IRQ: vector: 33 desc ffff9e84066df200
round 2:
          <idle>-0     [001] d.h.    75.580577: do_IRQ: vector: 33 desc ffffa0449d084a00
          <idle>-0     [001] d.h.    75.580578: xhci_irq: xhci irq
          <idle>-0     [001] d.h.    75.580639: do_IRQ: vector: 33 desc ffffa0449d084a00
          <idle>-0     [001] d.h.    75.580640: xhci_irq: xhci irq
           <...>-14    [001] d..1    75.585814: msi_set_affinity: direct update msi 123, vector 33 -> 33, apicid: 2 -> 6
     migration/3-24    [003] d..1    75.606381: msi_set_affinity: direct update msi 123, vector 33 -> 33, apicid: 6 -> 0
          <idle>-0     [000] d.h.    76.275792: do_IRQ: vector: 35 desc ffffa04486009a00

round 3:
          <idle>-0     [001] d.h.   117.383266: xhci_irq: xhci irq
          <idle>-0     [001] d.h.   117.383407: do_IRQ: vector: 33 desc ffff92515d0d5800
          <idle>-0     [001] d.h.   117.383410: xhci_irq: xhci irq
     migration/1-14    [001] d..1   117.388527: msi_set_affinity: direct update msi 123, vector 33 -> 33, apicid: 2 -> 6
     migration/3-24    [003] d..1   117.413877: msi_set_affinity: direct update msi 123, vector 33 -> 33, apicid: 6 -> 0
          <idle>-0     [000] d.h.   119.290474: do_IRQ: vector: 35 desc ffff92514757b600

round 4:
          <idle>-0     [003] d.h.   147.950569: do_IRQ: vector: 33 desc ffff976fdd04ca00
          <idle>-0     [003] d.h.   147.950569: xhci_irq: xhci irq
          <idle>-0     [003] d.h.   147.950689: do_IRQ: vector: 33 desc ffff976fdd04ca00
          <idle>-0     [003] d.h.   147.950690: xhci_irq: xhci irq
     migration/3-24    [003] d..1   147.951368: msi_set_affinity: direct update msi 123, vector 33 -> 33, apicid: 6 -> 0
          <idle>-0     [000] d.h.   148.491193: do_IRQ: vector: 35 desc ffff976fdcc9da00
          <idle>-0     [000] d.h.   148.491198: msi_set_affinity: direct update msi 122, vector 35 -> 35, apicid: 0 -> 0

-Mathias