Re: [PATCH v3 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff

From	David Hildenbrand <david@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff
Date	2016-12-16 17:50 +0100
Message-ID	<sP3RM-69y-3@gated-at.bofh.it> (permalink)
References	<sOHHA-8tl-5@gated-at.bofh.it> <sOHHA-8tl-35@gated-at.bofh.it>
Organization	Red Hat GmbH

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Am 15.12.2016 um 18:06 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.
>
> Fixes: 682f732ecf73 ("KVM: x86: bump MAX_VCPUS to 288")
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 

David

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[PATCH v3 0/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff Radim Krčmář <rkrcmar@redhat.com> - 2016-12-15 18:10 +0100
  [PATCH v3 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff Radim Krčmář <rkrcmar@redhat.com> - 2016-12-15 18:10 +0100
    Re: [PATCH v3 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over  0xff David Hildenbrand <david@redhat.com> - 2016-12-16 17:50 +0100

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