Re: [PATCH for-4.15] vtd: make sure QI/IR are disabled before initialisation

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Igor Druzhinin writes ("[PATCH for-4.15] vtd: make sure QI/IR are disabled 
before initialisation"):
> BIOS might pass control to Xen leaving QI and/or IR in enabled and/or
> partially configured state. In case of x2APIC code path where EIM is
> enabled early in boot - those are correctly disabled by Xen before any
> attempt to configure. But for xAPIC that step is missing which was
> proven to cause QI initialization failures on some ICX based platforms
> where QI is left pre-enabled and partially configured by BIOS.
> 
> Unify the behaviour between x2APIC and xAPIC code paths keeping that in
> line with what Linux does.

Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>