RE: [5.14-rc1] mlx5_core receives no interrupts with maxcpus=8

[Dexuan Cui <decui@microsoft.com>]

> From: Thomas Gleixner <tglx@linutronix.de>
> Sent: Wednesday, July 21, 2021 2:17 PM
> To: Dexuan Cui <decui@microsoft.com>; Saeed Mahameed
> 
> On Mon, Jul 19 2021 at 20:33, Dexuan Cui wrote:
> > This is a bare metal x86-64 host with Intel CPUs. Yes, I believe the
> > issue is in the IOMMU Interrupt Remapping mechanism rather in the
> > NIC driver. I just don't understand why bringing the CPUs online and
> > offline can work around the issue. I'm trying to dump the IOMMU IR
> > table entries to look for any error.
> 
> can you please enable GENERIC_IRQ_DEBUGFS and provide the output of
> 
> cat /sys/kernel/debug/irq/irqs/$THENICIRQS
> 
> Thanks,
> 
>         tglx

Sorry for the late response! I checked the below sys file, and the output is
exactly the same in the good/bad cases -- in both cases, I use maxcpus=8;
the only difference in the good case is that I online and then offline CPU 8~31:
for i in `seq 8 31`;  do echo 1 >  /sys/devices/system/cpu/cpu$i/online; done
for i in `seq 8 31`;  do echo 0 >  /sys/devices/system/cpu/cpu$i/online; done

# cat /sys/kernel/debug/irq/irqs/209
handler:  handle_edge_irq
device:   0000:d8:00.0
status:   0x00004000
istate:   0x00000000
ddepth:   0
wdepth:   0
dstate:   0x35409200
            IRQD_ACTIVATED
            IRQD_IRQ_STARTED
            IRQD_SINGLE_TARGET
            IRQD_MOVE_PCNTXT
            IRQD_AFFINITY_SET
            IRQD_AFFINITY_ON_ACTIVATE
            IRQD_CAN_RESERVE
            IRQD_HANDLE_ENFORCE_IRQCTX
node:     1
affinity: 0-7
effectiv: 5
pending:
domain:  INTEL-IR-MSI-3-3
 hwirq:   0x6c00000
 chip:    IR-PCI-MSI
  flags:   0x30
             IRQCHIP_SKIP_SET_WAKE
             IRQCHIP_ONESHOT_SAFE
 parent:
    domain:  INTEL-IR-3
     hwirq:   0x20000
     chip:    INTEL-IR
      flags:   0x0
     parent:
        domain:  VECTOR
         hwirq:   0xd1
         chip:    APIC
          flags:   0x0
         Vector:    42
         Target:     5
         move_in_progress: 0
         is_managed:       0
         can_reserve:      1
         has_reserved:     0
         cleanup_pending:  0

Thanks,
Dexuan