Messages in this thread | | | Subject | Re: [PATCH 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff | From | David Hildenbrand <> | Date | Mon, 5 Dec 2016 15:37:37 +0100 |
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Am 02.12.2016 um 20:44 schrieb Radim Krčmář: > 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.
Should we allow user space to turn it on/off for compatibility handling? Or do we just not care? (or how will this capability be used later on?)
--
David
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