diff options
| -rw-r--r-- | arch/arm64/kvm/vgic/vgic-init.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 1f33e71c2a73..0611a1c2ce8e 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -84,15 +84,40 @@ int kvm_vgic_create(struct kvm *kvm, u32 type) !kvm_vgic_global_state.can_emulate_gicv2) return -ENODEV; - /* Must be held to avoid race with vCPU creation */ + /* + * Ensure mutual exclusion with vCPU creation and any vCPU ioctls by: + * + * - Holding kvm->lock to prevent KVM_CREATE_VCPU from reaching + * kvm_arch_vcpu_precreate() and ensuring created_vcpus is stable. + * This alone is insufficient, as kvm_vm_ioctl_create_vcpu() drops + * the kvm->lock before completing the vCPU creation. + */ lockdep_assert_held(&kvm->lock); + /* + * - Acquiring the vCPU mutex for every *online* vCPU to prevent + * concurrent vCPU ioctls for vCPUs already visible to userspace. + */ ret = -EBUSY; if (!lock_all_vcpus(kvm)) return ret; + /* + * - Taking the config_lock which protects VGIC data structures such + * as the per-vCPU arrays of private IRQs (SGIs, PPIs). + */ mutex_lock(&kvm->arch.config_lock); + /* + * - Bailing on the entire thing if a vCPU is in the middle of creation, + * dropped the kvm->lock, but hasn't reached kvm_arch_vcpu_create(). + * + * The whole combination of this guarantees that no vCPU can get into + * KVM with a VGIC configuration inconsistent with the VM's VGIC. + */ + if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus)) + goto out_unlock; + if (irqchip_in_kernel(kvm)) { ret = -EEXIST; goto out_unlock; |