From: David Hildenbrand <david@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>, Igor Mammedov <imammedo@redhat.com>
Subject: Re: [PATCH v3 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff
Date: Fri, 16 Dec 2016 17:48:24 +0100 [thread overview]
Message-ID: <8cec3a67-1f2e-1475-52a5-65f06230599c@redhat.com> (raw)
In-Reply-To: <20161215170648.15714-5-rkrcmar@redhat.com>
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
prev parent reply other threads:[~2016-12-16 16:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-15 17:06 [PATCH v3 0/4] " Radim Krčmář
2016-12-15 17:06 ` [PATCH v3 1/4] KVM: x86: use delivery to self in hyperv synic Radim Krčmář
2016-12-15 17:06 ` [PATCH v3 2/4] KVM: x86: replace kvm_apic_id with kvm_{x,x2}apic_id Radim Krčmář
2016-12-16 15:41 ` David Hildenbrand
2016-12-15 17:06 ` [PATCH v3 3/4] KVM: x86: make interrupt delivery fast and slow path behave the same Radim Krčmář
2016-12-16 16:41 ` David Hildenbrand
2016-12-16 16:53 ` Paolo Bonzini
2016-12-16 17:07 ` [PATCH v4 " Radim Krčmář
2016-12-19 14:57 ` David Hildenbrand
2016-12-15 17:06 ` [PATCH v3 4/4] KVM: x86: allow hotplug of VCPU with APIC ID over 0xff Radim Krčmář
2016-12-16 16:48 ` David Hildenbrand [this message]
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