On Tue, Aug 23, 2022, Maxim Levitsky wrote: > Hi! > > I just noticed that this test fails when the AVIC is enabled. > > It seems that it exposes actual shortcomings in the AVIC hardware implementation, > although these should not matter in real life usage of it. > > > First of all it seems that AVIC just allows to set the APIC_ICR_BUSY bit (it should be read-only) > and it never clears it if set. > > Second AVIC seems to drop writes to low 24 bits of to ICR2, because these are not really used, > although technically not marked as reserved in the spec (though APIC_ID register in AMD spec, > states explicity that only bits 24-31 can be set, and the rest are reserved). > > And finally AVIC inhibit when x2apic is exposed to the guest was recently removed, > because in this case AVIC also works just fine (but with msr emulation) and that > means that we don't need anymore to hide x2apic from the guest to avoid AVIC inhibit. KUT's APIC test also fails for a variety of reasons when AVIC is enabled. https://lore.kernel.org/all/20220204214410.3315068-1-seanjc@xxxxxxxxxx
