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KVM: arm/arm64: Fix vgic init race

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The vgic_init function can race with kvm_arch_vcpu_create() which does
not hold kvm_lock() and we therefore have no synchronization primitives
to ensure we're doing the right thing.

As the user is trying to initialize or run the VM while at the same time
creating more VCPUs, we just have to refuse to initialize the VGIC in
this case rather than silently failing with a broken VCPU.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Christoffer Dall 2018-07-03 22:54:14 +02:00 committed by Marc Zyngier
parent de73708915
commit 1d47191de7
1 changed files with 4 additions and 0 deletions
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4
virt/kvm/arm/vgic/vgic-init.c
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@ -271,6 +271,10 @@ int vgic_init(struct kvm *kvm)
if (vgic_initialized(kvm))
return 0;
/* Are we also in the middle of creating a VCPU? */
if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
return -EBUSY;
/* freeze the number of spis */
if (!dist->nr_spis)
dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;