2016-12-07 13:03+0100, Paolo Bonzini: > On 02/12/2016 20:44, Radim Krčmář wrote: >> LAPIC after reset is in xAPIC mode, which poses a problem for hotplug of >> VCPUs with high APIC ID, because reset VCPU is waiting for INIT/SIPI, >> but there is no way to uniquely address it using xAPIC. >> >> From many possible options, we chose the one that also works on real >> hardware: accepting interrupts addressed to LAPIC's x2APIC ID even in >> xAPIC mode. >> >> KVM intentionally differs from real hardware, because real hardware >> (Knights Landing) does just "x2apic_id & 0xff" to decide whether to >> accept the interrupt in xAPIC mode and it can deliver one interrupt to >> more than one physical destination, e.g. 0x123 to 0x123 and 0x23. >> >> Add a capability to let userspace know that we do something now. > > I wouldn't even bother with the capability. It's a bit borderline for > stable, but I think it's okay. We can always Cc and let the maintainer > reject it.
Ok, David also mentioned that I should tone down compatibility ... Thanks to both, I'll prepare v2.
