Re: [PATCH RFC 1/2] x86/apic: Do not make an exception for PIC_CASCADE_IR when marking legacy irqs in irq_matrix

Thomas Gleixner
2021-03-18T10:10:52Z

On Thu, Mar 18 2021 at 09:29, Vitaly Kuznetsov wrote:
> Thomas Gleixner <tglx@linutronix.de> writes:
>> Out of paranoia I'd rather ignore that IO/APIC pin completely if it
>> claims to be IRQ2. I assume there is no device connected to it at all,
>> right?
>
> The original issue was observed on Amazon's r5d.xlarge instance
> type. Your assumption seems to be correct, I don't see any device on
> IRQ2.
>
>>
>> Can you please provide a dmesg with apic=verbose on the command line?
>>
>
> Here you go, attached.

> [ 0.931305] init IO_APIC IRQs
> [ 0.931312] IOAPIC[0]: Preconfigured routing entry (0-0 -> IRQ 0 Level:0 ActiveLow:0)
> [ 0.931316] IOAPIC[0]: Preconfigured routing entry (0-1 -> IRQ 1 Level:0 ActiveLow:0)

There you go:

> [ 0.931320] IOAPIC[0]: Preconfigured routing entry (0-2 -> IRQ 2 Level:0 ActiveLow:0)

Yet another virtualization feature :)

Thanks,

tglx