Is IRQ remapping similar or related to IRQ priorities?

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nick87720z
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Is IRQ remapping similar or related to IRQ priorities?

Post by nick87720z »

During attempt to optimize kernel configuration for my laptop, only this day I noticed option, which was disabled:

Code: Select all

  │ CONFIG_X86_X2APIC:
  │
  │ This enables x2apic support on CPUs that have this feature.
  │ 
  │ This allows 32-bit apic IDs (so it can support very large systems),
  │ and accesses the local apic via MSRs not via mmio.
  │
  │ If you don't know what to do here, say N.
  │
  │ Symbol: X86_X2APIC [=y]
  │ Type  : bool
  │ Prompt: Support x2apic
  │   Location:
  │     -> Processor type and features
I rebuild kernel with this option, but on reboot found this in dmesg:
[ 0.289191] x2apic: IRQ remapping doesn't support X2APIC mode

It looks different comparing to IRQ priorities, for whom there is rtirq. At least terms are different.

I have example of where it happens:
https://en.wikipedia.org/wiki/Input-out ... ement_unit

And some related discussion:
https://arstechnica.com/civis/viewtopic ... 0&t=899001

However, I can't find any info in context of audio optimizations or comparizons with IRQ priorities.
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