Commit c9bcd3e3 authored May 14, 2019 by Suthikulpanit, Suravee Committed by Paolo Bonzini May 24, 2019

kvm: svm/avic: fix off-by-one in checking host APIC ID



Current logic does not allow VCPU to be loaded onto CPU with
APIC ID 255. This should be allowed since the host physical APIC ID
field in the AVIC Physical APIC table entry is an 8-bit value,
and APIC ID 255 is valid in system with x2APIC enabled.
Instead, do not allow VCPU load if the host APIC ID cannot be
represented by an 8-bit value.

Also, use the more appropriate AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK
instead of AVIC_MAX_PHYSICAL_ID_COUNT.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 204c91ef

arch/x86/kvm/svm.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -2024,7 +2024,11 @@ static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
		if (!kvm_vcpu_apicv_active(vcpu))
		return;

		if (WARN_ON(h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT))
		/*
		* Since the host physical APIC id is 8 bits,
		* we can support host APIC ID upto 255.
		*/
		if (WARN_ON(h_physical_id > AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK))
		return;

		entry = READ_ONCE(*(svm->avic_physical_id_cache));

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